* SRR1 wake reason field for system reset interrupt on wakeup from nap
is now a 4-bit field on P8, compared to 3 bits on P7.
* Set PECEDP in LPCR when napping because of H_CEDE so guest doorbells
will wake us up.
* Waking up from nap because of a guest doorbell interrupt is not a
reason to exit the guest.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
Currently in book3s_hv_rmhandlers.S we have three places where we
have woken up from nap mode and we check the reason field in SRR1
to see what event woke us up. This consolidates them into a new
function, kvmppc_check_wake_reason. It looks at the wake reason
field in SRR1, and if it indicates that an external interrupt caused
the wakeup, calls kvmppc_read_intr to check what sort of interrupt
it was.
This also consolidates the two places where we synthesize an external
interrupt (0x500 vector) for the guest. Now, if the guest exit code
finds that there was an external interrupt which has been handled
(i.e. it was an IPI indicating that there is now an interrupt pending
for the guest), it jumps to deliver_guest_interrupt, which is in the
last part of the guest entry code, where we synthesize guest external
and decrementer interrupts. That code has been streamlined a little
and now clears LPCR[MER] when appropriate as well as setting it.
The extra clearing of any pending IPI on a secondary, offline CPU
thread before going back to nap mode has been removed. It is no longer
necessary now that we have code to read and acknowledge IPIs in the
guest exit path.
This fixes a minor bug in the H_CEDE real-mode handling - previously,
if we found that other threads were already exiting the guest when we
were about to go to nap mode, we would branch to the cede wakeup path
and end up looking in SRR1 for a wakeup reason. Now we branch to a
point after we have checked the wakeup reason.
This also fixes a minor bug in kvmppc_read_intr - previously it could
return 0xff rather than 1, in the case where we find that a host IPI
is pending after we have cleared the IPI. Now it returns 1.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
POWER8 has 512 sets in the TLB, compared to 128 for POWER7, so we need
to do more tlbiel instructions when flushing the TLB on POWER8.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
This adds fields to the struct kvm_vcpu_arch to store the new
guest-accessible SPRs on POWER8, adds code to the get/set_one_reg
functions to allow userspace to access this state, and adds code to
the guest entry and exit to context-switch these SPRs between host
and guest.
Note that DPDES (Directed Privileged Doorbell Exception State) is
shared between threads on a core; hence we store it in struct
kvmppc_vcore and have the master thread save and restore it.
Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
On a threaded processor such as POWER7, we group VCPUs into virtual
cores and arrange that the VCPUs in a virtual core run on the same
physical core. Currently we don't enforce any correspondence between
virtual thread numbers within a virtual core and physical thread
numbers. Physical threads are allocated starting at 0 on a first-come
first-served basis to runnable virtual threads (VCPUs).
POWER8 implements a new "msgsndp" instruction which guest kernels can
use to interrupt other threads in the same core or sub-core. Since
the instruction takes the destination physical thread ID as a parameter,
it becomes necessary to align the physical thread IDs with the virtual
thread IDs, that is, to make sure virtual thread N within a virtual
core always runs on physical thread N.
This means that it's possible that thread 0, which is where we call
__kvmppc_vcore_entry, may end up running some other vcpu than the
one whose task called kvmppc_run_core(), or it may end up running
no vcpu at all, if for example thread 0 of the virtual core is
currently executing in userspace. However, we do need thread 0
to be responsible for switching the MMU -- a previous version of
this patch that had other threads switching the MMU was found to
be responsible for occasional memory corruption and machine check
interrupts in the guest on POWER7 machines.
To accommodate this, we no longer pass the vcpu pointer to
__kvmppc_vcore_entry, but instead let the assembly code load it from
the PACA. Since the assembly code will need to know the kvm pointer
and the thread ID for threads which don't have a vcpu, we move the
thread ID into the PACA and we add a kvm pointer to the virtual core
structure.
In the case where thread 0 has no vcpu to run, it still calls into
kvmppc_hv_entry in order to do the MMU switch, and then naps until
either its vcpu is ready to run in the guest, or some other thread
needs to exit the guest. In the latter case, thread 0 jumps to the
code that switches the MMU back to the host. This control flow means
that now we switch the MMU before loading any guest vcpu state.
Similarly, on guest exit we now save all the guest vcpu state before
switching the MMU back to the host. This has required substantial
code movement, making the diff rather large.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
POWER8 doesn't have the DABR and DABRX registers; instead it has
new DAWR/DAWRX registers, which will be handled in a later patch.
Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
This modifies kvmppc_load_fp and kvmppc_save_fp to use the generic
FP/VSX and VMX load/store functions instead of open-coding the
FP/VSX/VMX load/store instructions. Since kvmppc_load/save_fp don't
follow C calling conventions, we make them private symbols within
book3s_hv_rmhandlers.S.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
This uses struct thread_fp_state and struct thread_vr_state to store
the floating-point, VMX/Altivec and VSX state, rather than flat arrays.
This makes transferring the state to/from the thread_struct simpler
and allows us to unify the get/set_one_reg implementations for the
VSX registers.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
We don't use PACATOC for PR. Avoid updating HOST_R2 with PR
KVM mode when both HV and PR are enabled in the kernel. Without this we
get the below crash
(qemu)
Unable to handle kernel paging request for data at address 0xffffffffffff8310
Faulting instruction address: 0xc00000000001d5a4
cpu 0x2: Vector: 300 (Data Access) at [c0000001dc53aef0]
pc: c00000000001d5a4: .vtime_delta.isra.1+0x34/0x1d0
lr: c00000000001d760: .vtime_account_system+0x20/0x60
sp: c0000001dc53b170
msr: 8000000000009032
dar: ffffffffffff8310
dsisr: 40000000
current = 0xc0000001d76c62d0
paca = 0xc00000000fef1100 softe: 0 irq_happened: 0x01
pid = 4472, comm = qemu-system-ppc
enter ? for help
[c0000001dc53b200] c00000000001d760 .vtime_account_system+0x20/0x60
[c0000001dc53b290] c00000000008d050 .kvmppc_handle_exit_pr+0x60/0xa50
[c0000001dc53b340] c00000000008f51c kvm_start_lightweight+0xb4/0xc4
[c0000001dc53b510] c00000000008cdf0 .kvmppc_vcpu_run_pr+0x150/0x2e0
[c0000001dc53b9e0] c00000000008341c .kvmppc_vcpu_run+0x2c/0x40
[c0000001dc53ba50] c000000000080af4 .kvm_arch_vcpu_ioctl_run+0x54/0x1b0
[c0000001dc53bae0] c00000000007b4c8 .kvm_vcpu_ioctl+0x478/0x730
[c0000001dc53bca0] c0000000002140cc .do_vfs_ioctl+0x4ac/0x770
[c0000001dc53bd80] c0000000002143e8 .SyS_ioctl+0x58/0xb0
[c0000001dc53be30] c000000000009e58 syscall_exit+0x0/0x98
Signed-off-by: Alexander Graf <agraf@suse.de>
In some scene, e.g openstack CI, PR guest can trigger "sc 1" frequently,
this patch optimizes the path by directly delivering BOOK3S_INTERRUPT_SYSCALL
to HV guest, so powernv can return to HV guest without heavy exit, i.e,
no need to swap TLB, HTAB,.. etc
Signed-off-by: Liu Ping Fan <pingfank@linux.vnet.ibm.com>
Signed-off-by: Alexander Graf <agraf@suse.de>
Some users have reported instances of the host hanging with secondary
threads of a core waiting for the primary thread to exit the guest,
and the primary thread stuck in nap mode. This prompted a review of
the memory barriers in the guest entry/exit code, and this is the
result. Most of these changes are the suggestions of Dean Burdick
<deanburdick@us.ibm.com>.
The barriers between updating napping_threads and reading the
entry_exit_count on the one hand, and updating entry_exit_count and
reading napping_threads on the other, need to be isync not lwsync,
since we need to ensure that either the napping_threads update or the
entry_exit_count update get seen. It is not sufficient to order the
load vs. lwarx, as lwsync does; we need to order the load vs. the
stwcx., so we need isync.
In addition, we need a full sync before sending IPIs to wake other
threads from nap, to ensure that the write to the entry_exit_count is
visible before the IPI occurs.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
With this patch if HV is included, interrupts come in to the HV version
of the kvmppc_interrupt code, which then jumps to the PR handler,
renamed to kvmppc_interrupt_pr, if the guest is a PR guest. This helps
in enabling both HV and PR, which we do in later patch
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Alexander Graf <agraf@suse.de>
When an interrupt or exception happens in the guest that comes to the
host, the CPU goes to hypervisor real mode (MMU off) to handle the
exception but doesn't change the MMU context. After saving a few
registers, we then clear the "in guest" flag. If, for any reason,
we get an exception in the real-mode code, that then gets handled
by the normal kernel exception handlers, which turn the MMU on. This
is disastrous if the MMU is still set to the guest context, since we
end up executing instructions from random places in the guest kernel
with hypervisor privilege.
In order to catch this situation, we define a new value for the "in guest"
flag, KVM_GUEST_MODE_HOST_HV, to indicate that we are in hypervisor real
mode with guest MMU context. If the "in guest" flag is set to this value,
we branch off to an emergency handler. For the moment, this just does
a branch to self to stop the CPU from doing anything further.
While we're here, we define another new flag value to indicate that we
are in a HV guest, as distinct from a PR guest. This will be useful
when we have a kernel that can support both PR and HV guests concurrently.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
Both PR and HV KVM have separate, identical copies of the
kvmppc_skip_interrupt and kvmppc_skip_Hinterrupt handlers that are
used for the situation where an interrupt happens when loading the
instruction that caused an exit from the guest. To eliminate this
duplication and make it easier to compile in both PR and HV KVM,
this moves this code to arch/powerpc/kernel/exceptions-64s.S along
with other kernel interrupt handler code.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
This enables us to use the Processor Compatibility Register (PCR) on
POWER7 to put the processor into architecture 2.05 compatibility mode
when running a guest. In this mode the new instructions and registers
that were introduced on POWER7 are disabled in user mode. This
includes all the VSX facilities plus several other instructions such
as ldbrx, stdbrx, popcntw, popcntd, etc.
To select this mode, we have a new register accessible through the
set/get_one_reg interface, called KVM_REG_PPC_ARCH_COMPAT. Setting
this to zero gives the full set of capabilities of the processor.
Setting it to one of the "logical" PVR values defined in PAPR puts
the vcpu into the compatibility mode for the corresponding
architecture level. The supported values are:
0x0f000002 Architecture 2.05 (POWER6)
0x0f000003 Architecture 2.06 (POWER7)
0x0f100003 Architecture 2.06+ (POWER7+)
Since the PCR is per-core, the architecture compatibility level and
the corresponding PCR value are stored in the struct kvmppc_vcore, and
are therefore shared between all vcpus in a virtual core.
Signed-off-by: Paul Mackerras <paulus@samba.org>
[agraf: squash in fix to add missing break statements and documentation]
Signed-off-by: Alexander Graf <agraf@suse.de>
POWER7 and later IBM server processors have a register called the
Program Priority Register (PPR), which controls the priority of
each hardware CPU SMT thread, and affects how fast it runs compared
to other SMT threads. This priority can be controlled by writing to
the PPR or by use of a set of instructions of the form or rN,rN,rN
which are otherwise no-ops but have been defined to set the priority
to particular levels.
This adds code to context switch the PPR when entering and exiting
guests and to make the PPR value accessible through the SET/GET_ONE_REG
interface. When entering the guest, we set the PPR as late as
possible, because if we are setting a low thread priority it will
make the code run slowly from that point on. Similarly, the
first-level interrupt handlers save the PPR value in the PACA very
early on, and set the thread priority to the medium level, so that
the interrupt handling code runs at a reasonable speed.
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
This adds the ability to have a separate LPCR (Logical Partitioning
Control Register) value relating to a guest for each virtual core,
rather than only having a single value for the whole VM. This
corresponds to what real POWER hardware does, where there is a LPCR
per CPU thread but most of the fields are required to have the same
value on all active threads in a core.
The per-virtual-core LPCR can be read and written using the
GET/SET_ONE_REG interface. Userspace can can only modify the
following fields of the LPCR value:
DPFD Default prefetch depth
ILE Interrupt little-endian
TC Translation control (secondary HPT hash group search disable)
We still maintain a per-VM default LPCR value in kvm->arch.lpcr, which
contains bits relating to memory management, i.e. the Virtualized
Partition Memory (VPM) bits and the bits relating to guest real mode.
When this default value is updated, the update needs to be propagated
to the per-vcore values, so we add a kvmppc_update_lpcr() helper to do
that.
Signed-off-by: Paul Mackerras <paulus@samba.org>
[agraf: fix whitespace]
Signed-off-by: Alexander Graf <agraf@suse.de>
The yield count in the VPA is supposed to be incremented every time
we enter the guest, and every time we exit the guest, so that its
value is even when the vcpu is running in the guest and odd when it
isn't. However, it's currently possible that we increment the yield
count on the way into the guest but then find that other CPU threads
are already exiting the guest, so we go back to nap mode via the
secondary_too_late label. In this situation we don't increment the
yield count again, breaking the relationship between the LSB of the
count and whether the vcpu is in the guest.
To fix this, we move the increment of the yield count to a point
after we have checked whether other CPU threads are exiting.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
This moves the code in book3s_hv_rmhandlers.S that reads any pending
interrupt from the XICS interrupt controller, and works out whether
it is an IPI for the guest, an IPI for the host, or a device interrupt,
into a new function called kvmppc_read_intr. Later patches will
need this.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
We have two paths into and out of the low-level guest entry and exit
code: from a vcpu task via kvmppc_hv_entry_trampoline, and from the
system reset vector for an offline secondary thread on POWER7 via
kvm_start_guest. Currently both just branch to kvmppc_hv_entry to
enter the guest, and on guest exit, we test the vcpu physical thread
ID to detect which way we came in and thus whether we should return
to the vcpu task or go back to nap mode.
In order to make the code flow clearer, and to keep the code relating
to each flow together, this turns kvmppc_hv_entry into a subroutine
that follows the normal conventions for call and return. This means
that kvmppc_hv_entry_trampoline() and kvmppc_hv_entry() now establish
normal stack frames, and we use the normal stack slots for saving
return addresses rather than local_paca->kvm_hstate.vmhandler. Apart
from that this is mostly moving code around unchanged.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
This allows guests to have a different timebase origin from the host.
This is needed for migration, where a guest can migrate from one host
to another and the two hosts might have a different timebase origin.
However, the timebase seen by the guest must not go backwards, and
should go forwards only by a small amount corresponding to the time
taken for the migration.
Therefore this provides a new per-vcpu value accessed via the one_reg
interface using the new KVM_REG_PPC_TB_OFFSET identifier. This value
defaults to 0 and is not modified by KVM. On entering the guest, this
value is added onto the timebase, and on exiting the guest, it is
subtracted from the timebase.
This is only supported for recent POWER hardware which has the TBU40
(timebase upper 40 bits) register. Writing to the TBU40 register only
alters the upper 40 bits of the timebase, leaving the lower 24 bits
unchanged. This provides a way to modify the timebase for guest
migration without disturbing the synchronization of the timebase
registers across CPU cores. The kernel rounds up the value given
to a multiple of 2^24.
Timebase values stored in KVM structures (struct kvm_vcpu, struct
kvmppc_vcore, etc.) are stored as host timebase values. The timebase
values in the dispatch trace log need to be guest timebase values,
however, since that is read directly by the guest. This moves the
setting of vcpu->arch.dec_expires on guest exit to a point after we
have restored the host timebase so that vcpu->arch.dec_expires is a
host timebase value.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
Currently we are not saving and restoring the SIAR and SDAR registers in
the PMU (performance monitor unit) on guest entry and exit. The result
is that performance monitoring tools in the guest could get false
information about where a program was executing and what data it was
accessing at the time of a performance monitor interrupt. This fixes
it by saving and restoring these registers along with the other PMU
registers on guest entry/exit.
This also provides a way for userspace to access these values for a
vcpu via the one_reg interface.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
This fixes a typo in the code that saves the guest DSCR (Data Stream
Control Register) into the kvm_vcpu_arch struct on guest exit. The
effect of the typo was that the DSCR value was saved in the wrong place,
so changes to the DSCR by the guest didn't persist across guest exit
and entry, and some host kernel memory got corrupted.
Cc: stable@vger.kernel.org [v3.1+]
Signed-off-by: Paul Mackerras <paulus@samba.org>
Acked-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Pull powerpc updates from Ben Herrenschmidt:
"Here's the powerpc batch for this merge window. Some of the
highlights are:
- A bunch of endian fixes ! We don't have full LE support yet in that
release but this contains a lot of fixes all over arch/powerpc to
use the proper accessors, call the firmware with the right endian
mode, etc...
- A few updates to our "powernv" platform (non-virtualized, the one
to run KVM on), among other, support for bridging the P8 LPC bus
for UARTs, support and some EEH fixes.
- Some mpc51xx clock API cleanups in preparation for a clock API
overhaul
- A pile of cleanups of our old math emulation code, including better
support for using it to emulate optional FP instructions on
embedded chips that otherwise have a HW FPU.
- Some infrastructure in selftest, for powerpc now, but could be
generalized, initially used by some tests for our perf instruction
counting code.
- A pile of fixes for hotplug on pseries (that was seriously
bitrotting)
- The usual slew of freescale embedded updates, new boards, 64-bit
hiberation support, e6500 core PMU support, etc..."
* 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/benh/powerpc: (146 commits)
powerpc: Correct FSCR bit definitions
powerpc/xmon: Fix printing of set of CPUs in xmon
powerpc/pseries: Move lparcfg.c to platforms/pseries
powerpc/powernv: Return secondary CPUs to firmware on kexec
powerpc/btext: Fix CONFIG_PPC_EARLY_DEBUG_BOOTX on ppc32
powerpc: Cleanup handling of the DSCR bit in the FSCR register
powerpc/pseries: Child nodes are not detached by dlpar_detach_node
powerpc/pseries: Add mising of_node_put in delete_dt_node
powerpc/pseries: Make dlpar_configure_connector parent node aware
powerpc/pseries: Do all node initialization in dlpar_parse_cc_node
powerpc/pseries: Fix parsing of initial node path in update_dt_node
powerpc/pseries: Pack update_props_workarea to map correctly to rtas buffer header
powerpc/pseries: Fix over writing of rtas return code in update_dt_node
powerpc/pseries: Fix creation of loop in device node property list
powerpc: Skip emulating & leave interrupts off for kernel program checks
powerpc: Add more exception trampolines for hypervisor exceptions
powerpc: Fix location and rename exception trampolines
powerpc: Add more trap names to xmon
powerpc/pseries: Add a warning in the case of cross-cpu VPA registration
powerpc: Update the 00-Index in Documentation/powerpc
...
Our ppc64 spinlocks and rwlocks use a trick where a lock token and
the paca index are placed in the lock with a single store. Since we
are using two u16s they need adjusting for little endian.
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
The lppaca, slb_shadow and dtl_entry hypervisor structures are
big endian, so we have to byte swap them in little endian builds.
LE KVM hosts will also need to be fixed but for now add an #error
to remind us.
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
The table of offsets to real-mode hcall handlers in book3s_hv_rmhandlers.S
can contain negative values, if some of the handlers end up before the
table in the vmlinux binary. Thus we need to use a sign-extending load
to read the values in the table rather than a zero-extending load.
Without this, the host crashes when the guest does one of the hcalls
with negative offsets, due to jumping to a bogus address.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
This streamlines our handling of external interrupts that come in
while we're in the guest. First, when waking up a hardware thread
that was napping, we split off the "napping due to H_CEDE" case
earlier, and use the code that handles an external interrupt (0x500)
in the guest to handle that too. Secondly, the code that handles
those external interrupts now checks if any other thread is exiting
to the host before bouncing an external interrupt to the guest, and
also checks that there is actually an external interrupt pending for
the guest before setting the LPCR MER bit (mediated external request).
This also makes sure that we clear the "ceded" flag when we handle a
wakeup from cede in real mode, and fixes a potential infinite loop
in kvmppc_run_vcpu() which can occur if we ever end up with the ceded
flag set but MSR[EE] off.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
This adds an implementation of the XICS hypercalls in real mode for HV
KVM, which allows us to avoid exiting the guest MMU context on all
threads for a variety of operations such as fetching a pending
interrupt, EOI of messages, IPIs, etc.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
Currently, we wake up a CPU by sending a host IPI with
smp_send_reschedule() to thread 0 of that core, which will take all
threads out of the guest, and cause them to re-evaluate their
interrupt status on the way back in.
This adds a mechanism to differentiate real host IPIs from IPIs sent
by KVM for guest threads to poke each other, in order to target the
guest threads precisely when possible and avoid that global switch of
the core to host state.
We then use this new facility in the in-kernel XICS code.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
At present, the KVM_GET_DIRTY_LOG ioctl doesn't report modifications
done by the host to the virtual processor areas (VPAs) and dispatch
trace logs (DTLs) registered by the guest. This is because those
modifications are done either in real mode or in the host kernel
context, and in neither case does the access go through the guest's
HPT, and thus no change (C) bit gets set in the guest's HPT.
However, the changes done by the host do need to be tracked so that
the modified pages get transferred when doing live migration. In
order to track these modifications, this adds a dirty flag to the
struct representing the VPA/DTL areas, and arranges to set the flag
when the VPA/DTL gets modified by the host. Then, when we are
collecting the dirty log, we also check the dirty flags for the
VPA and DTL for each vcpu and set the relevant bit in the dirty log
if necessary. Doing this also means we now need to keep track of
the guest physical address of the VPA/DTL areas.
So as not to lose track of modifications to a VPA/DTL area when it gets
unregistered, or when a new area gets registered in its place, we need
to transfer the dirty state to the rmap chain. This adds code to
kvmppc_unpin_guest_page() to do that if the area was dirty. To simplify
that code, we now require that all VPA, DTL and SLB shadow buffer areas
fit within a single host page. Guests already comply with this
requirement because pHyp requires that these areas not cross a 4k
boundary.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
The CFAR (Come-From Address Register) is a useful debugging aid that
exists on POWER7 processors. Currently HV KVM doesn't save or restore
the CFAR register for guest vcpus, making the CFAR of limited use in
guests.
This adds the necessary code to capture the CFAR value saved in the
early exception entry code (it has to be saved before any branch is
executed), save it in the vcpu.arch struct, and restore it on entry
to the guest.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Currently, if a machine check interrupt happens while we are in the
guest, we exit the guest and call the host's machine check handler,
which tends to cause the host to panic. Some machine checks can be
triggered by the guest; for example, if the guest creates two entries
in the SLB that map the same effective address, and then accesses that
effective address, the CPU will take a machine check interrupt.
To handle this better, when a machine check happens inside the guest,
we call a new function, kvmppc_realmode_machine_check(), while still in
real mode before exiting the guest. On POWER7, it handles the cases
that the guest can trigger, either by flushing and reloading the SLB,
or by flushing the TLB, and then it delivers the machine check interrupt
directly to the guest without going back to the host. On POWER7, the
OPAL firmware patches the machine check interrupt vector so that it
gets control first, and it leaves behind its analysis of the situation
in a structure pointed to by the opal_mc_evt field of the paca. The
kvmppc_realmode_machine_check() function looks at this, and if OPAL
reports that there was no error, or that it has handled the error, we
also go straight back to the guest with a machine check. We have to
deliver a machine check to the guest since the machine check interrupt
might have trashed valid values in SRR0/1.
If the machine check is one we can't handle in real mode, and one that
OPAL hasn't already handled, or on PPC970, we exit the guest and call
the host's machine check handler. We do this by jumping to the
machine_check_fwnmi label, rather than absolute address 0x200, because
we don't want to re-execute OPAL's handler on POWER7. On PPC970, the
two are equivalent because address 0x200 just contains a branch.
Then, if the host machine check handler decides that the system can
continue executing, kvmppc_handle_exit() delivers a machine check
interrupt to the guest -- once again to let the guest know that SRR0/1
have been modified.
Signed-off-by: Paul Mackerras <paulus@samba.org>
[agraf: fix checkpatch warnings]
Signed-off-by: Alexander Graf <agraf@suse.de>
When we change or remove a HPT (hashed page table) entry, we can do
either a global TLB invalidation (tlbie) that works across the whole
machine, or a local invalidation (tlbiel) that only affects this core.
Currently we do local invalidations if the VM has only one vcpu or if
the guest requests it with the H_LOCAL flag, though the guest Linux
kernel currently doesn't ever use H_LOCAL. Then, to cope with the
possibility that vcpus moving around to different physical cores might
expose stale TLB entries, there is some code in kvmppc_hv_entry to
flush the whole TLB of entries for this VM if either this vcpu is now
running on a different physical core from where it last ran, or if this
physical core last ran a different vcpu.
There are a number of problems on POWER7 with this as it stands:
- The TLB invalidation is done per thread, whereas it only needs to be
done per core, since the TLB is shared between the threads.
- With the possibility of the host paging out guest pages, the use of
H_LOCAL by an SMP guest is dangerous since the guest could possibly
retain and use a stale TLB entry pointing to a page that had been
removed from the guest.
- The TLB invalidations that we do when a vcpu moves from one physical
core to another are unnecessary in the case of an SMP guest that isn't
using H_LOCAL.
- The optimization of using local invalidations rather than global should
apply to guests with one virtual core, not just one vcpu.
(None of this applies on PPC970, since there we always have to
invalidate the whole TLB when entering and leaving the guest, and we
can't support paging out guest memory.)
To fix these problems and simplify the code, we now maintain a simple
cpumask of which cpus need to flush the TLB on entry to the guest.
(This is indexed by cpu, though we only ever use the bits for thread
0 of each core.) Whenever we do a local TLB invalidation, we set the
bits for every cpu except the bit for thread 0 of the core that we're
currently running on. Whenever we enter a guest, we test and clear the
bit for our core, and flush the TLB if it was set.
On initial startup of the VM, and when resetting the HPT, we set all the
bits in the need_tlb_flush cpumask, since any core could potentially have
stale TLB entries from the previous VM to use the same LPID, or the
previous contents of the HPT.
Then, we maintain a count of the number of online virtual cores, and use
that when deciding whether to use a local invalidation rather than the
number of online vcpus. The code to make that decision is extracted out
into a new function, global_invalidates(). For multi-core guests on
POWER7 (i.e. when we are using mmu notifiers), we now never do local
invalidations regardless of the H_LOCAL flag.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
Subsequent patches implementing in-kernel XICS emulation will make it
possible for IPIs to arrive at secondary threads at arbitrary times.
This fixes some races in how we start the secondary threads, which
if not fixed could lead to occasional crashes of the host kernel.
This makes sure that (a) we have grabbed all the secondary threads,
and verified that they are no longer in the kernel, before we start
any thread, (b) that the secondary thread loads its vcpu pointer
after clearing the IPI that woke it up (so we don't miss a wakeup),
and (c) that the secondary thread clears its vcpu pointer before
incrementing the nap count. It also removes unnecessary setting
of the vcpu and vcore pointers in the paca in kvmppc_core_vcpu_load.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
Critical exception on 64-bit booke uses user-visible SPRG3 as scratch.
Restore VDSO information in SPRG3 on exception prolog.
Use a common sprg3 field in PACA for all powerpc64 architectures.
Signed-off-by: Mihai Caraman <mihai.caraman@freescale.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
In handling the H_CEDE hypercall, if this vcpu has already been
prodded (with the H_PROD hypercall, which Linux guests don't in fact
use), we branch to a numeric label '1f'. Unfortunately there is
another '1:' label before the one that we want to jump to. This fixes
the problem by using a textual label, 'kvm_cede_prodded'. It also
changes the label for another longish branch from '2:' to
'kvm_cede_exit' to avoid a possible future problem if code modifications
add another numeric '2:' label in between.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
We have a request for a fast method of getting CPU and NUMA node IDs
from userspace. This patch implements a getcpu VDSO function,
similar to x86.
Ben suggested we use SPRG3 which is userspace readable. SPRG3 can be
modified by a KVM guest, so we save the SPRG3 value in the paca and
restore it when transitioning from the guest to the host.
I have a glibc patch that implements sched_getcpu on top of this.
Testing on a POWER7:
baseline: 538 cycles
vdso: 30 cycles
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Merge the defines of VCPU_GPR from different places.
Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Anything that uses a constructed instruction (ie. from ppc-opcode.h),
need to use the new R0 macro, as %r0 is not going to work.
Also convert usages of macros where we are just determining an offset
(usually for a load/store), like:
std r14,STK_REG(r14)(r1)
Can't use STK_REG(r14) as %r14 doesn't work in the STK_REG macro since
it's just calculating an offset.
Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Since we are taking a registers, this should never have been an sldi.
Talking to paulus offline, this is the correct fix.
Was introduced by:
commit 19ccb76a19
Author: Paul Mackerras <paulus@samba.org>
Date: Sat Jul 23 17:42:46 2011 +1000
Talking to paulus, this shouldn't be a literal.
Signed-off-by: Michael Neuling <mikey@neuling.org>
CC: <stable@kernel.org> [v3.2+]
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
It turns out that on POWER7, writing to the DABR can cause a corrupted
value to be written if the PMU is active and updating SDAR in continuous
sampling mode. To work around this, we make sure that the PMU is inactive
and SDAR updates are disabled (via MMCRA) when we are context-switching
DABR.
When the guest sets DABR via the H_SET_DABR hypercall, we use a slightly
different workaround, which is to read back the DABR and write it again
if it got corrupted.
While we are at it, make it consistent that the saving and restoring
of the guest's non-volatile GPRs and the FPRs are done with the guest
setup of the PMU active.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>
Currently on POWER7, if we are running the guest on a core and we don't
need all the hardware threads, we do nothing to ensure that the unused
threads aren't executing in the kernel (other than checking that they
are offline). We just assume they're napping and we don't do anything
to stop them trying to enter the kernel while the guest is running.
This means that a stray IPI can wake up the hardware thread and it will
then try to enter the kernel, but since the core is in guest context,
it will execute code from the guest in hypervisor mode once it turns the
MMU on, which tends to lead to crashes or hangs in the host.
This fixes the problem by adding two new one-byte flags in the
kvmppc_host_state structure in the PACA which are used to interlock
between the primary thread and the unused secondary threads when entering
the guest. With these flags, the primary thread can ensure that the
unused secondaries are not already in kernel mode (i.e. handling a stray
IPI) and then indicate that they should not try to enter the kernel
if they do get woken for any reason. Instead they will go into KVM code,
find that there is no vcpu to run, acknowledge and clear the IPI and go
back to nap mode.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>
With this, if a guest does an H_ENTER with a read/write HPTE on a page
which is currently read-only, we make the actual HPTE inserted be a
read-only version of the HPTE. We now intercept protection faults as
well as HPTE not found faults, and for a protection fault we work out
whether it should be reflected to the guest (e.g. because the guest HPTE
didn't allow write access to usermode) or handled by switching to
kernel context and calling kvmppc_book3s_hv_page_fault, which will then
request write access to the page and update the actual HPTE.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>
This adds the infrastructure to enable us to page out pages underneath
a Book3S HV guest, on processors that support virtualized partition
memory, that is, POWER7. Instead of pinning all the guest's pages,
we now look in the host userspace Linux page tables to find the
mapping for a given guest page. Then, if the userspace Linux PTE
gets invalidated, kvm_unmap_hva() gets called for that address, and
we replace all the guest HPTEs that refer to that page with absent
HPTEs, i.e. ones with the valid bit clear and the HPTE_V_ABSENT bit
set, which will cause an HDSI when the guest tries to access them.
Finally, the page fault handler is extended to reinstantiate the
guest HPTE when the guest tries to access a page which has been paged
out.
Since we can't intercept the guest DSI and ISI interrupts on PPC970,
we still have to pin all the guest pages on PPC970. We have a new flag,
kvm->arch.using_mmu_notifiers, that indicates whether we can page
guest pages out. If it is not set, the MMU notifier callbacks do
nothing and everything operates as before.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>
This provides the low-level support for MMIO emulation in Book3S HV
guests. When the guest tries to map a page which is not covered by
any memslot, that page is taken to be an MMIO emulation page. Instead
of inserting a valid HPTE, we insert an HPTE that has the valid bit
clear but another hypervisor software-use bit set, which we call
HPTE_V_ABSENT, to indicate that this is an absent page. An
absent page is treated much like a valid page as far as guest hcalls
(H_ENTER, H_REMOVE, H_READ etc.) are concerned, except of course that
an absent HPTE doesn't need to be invalidated with tlbie since it
was never valid as far as the hardware is concerned.
When the guest accesses a page for which there is an absent HPTE, it
will take a hypervisor data storage interrupt (HDSI) since we now set
the VPM1 bit in the LPCR. Our HDSI handler for HPTE-not-present faults
looks up the hash table and if it finds an absent HPTE mapping the
requested virtual address, will switch to kernel mode and handle the
fault in kvmppc_book3s_hv_page_fault(), which at present just calls
kvmppc_hv_emulate_mmio() to set up the MMIO emulation.
This is based on an earlier patch by Benjamin Herrenschmidt, but since
heavily reworked.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>
This fixes a problem where a CPU thread coming out of nap mode can
think it has valid values in the nonvolatile GPRs (r14 - r31) as saved
away in power7_idle, but in fact the values have been trashed because
the thread was used for KVM in the mean time. The result is that the
thread crashes because code that called power7_idle (e.g.,
pnv_smp_cpu_kill_self()) goes to use values in registers that have
been trashed.
The bit field in SRR1 that tells whether state was lost only reflects
the most recent nap, which may not have been the nap instruction in
power7_idle. So we need an extra PACA field to indicate that state
has been lost even if SRR1 indicates that the most recent nap didn't
lose state. We clear this field when saving the state in power7_idle,
we set it to a non-zero value when we use the thread for KVM, and we
test it in power7_wakeup_noloss.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
With a KVM guest operating in SMT4 mode (i.e. 4 hardware threads per
core), whenever a CPU goes idle, we have to pull all the other
hardware threads in the core out of the guest, because the H_CEDE
hcall is handled in the kernel. This is inefficient.
This adds code to book3s_hv_rmhandlers.S to handle the H_CEDE hcall
in real mode. When a guest vcpu does an H_CEDE hcall, we now only
exit to the kernel if all the other vcpus in the same core are also
idle. Otherwise we mark this vcpu as napping, save state that could
be lost in nap mode (mainly GPRs and FPRs), and execute the nap
instruction. When the thread wakes up, because of a decrementer or
external interrupt, we come back in at kvm_start_guest (from the
system reset interrupt vector), find the `napping' flag set in the
paca, and go to the resume path.
This has some other ramifications. First, when starting a core, we
now start all the threads, both those that are immediately runnable and
those that are idle. This is so that we don't have to pull all the
threads out of the guest when an idle thread gets a decrementer interrupt
and wants to start running. In fact the idle threads will all start
with the H_CEDE hcall returning; being idle they will just do another
H_CEDE immediately and go to nap mode.
This required some changes to kvmppc_run_core() and kvmppc_run_vcpu().
These functions have been restructured to make them simpler and clearer.
We introduce a level of indirection in the wait queue that gets woken
when external and decrementer interrupts get generated for a vcpu, so
that we can have the 4 vcpus in a vcore using the same wait queue.
We need this because the 4 vcpus are being handled by one thread.
Secondly, when we need to exit from the guest to the kernel, we now
have to generate an IPI for any napping threads, because an HDEC
interrupt doesn't wake up a napping thread.
Thirdly, we now need to be able to handle virtual external interrupts
and decrementer interrupts becoming pending while a thread is napping,
and deliver those interrupts to the guest when the thread wakes.
This is done in kvmppc_cede_reentry, just before fast_guest_return.
Finally, since we are not using the generic kvm_vcpu_block for book3s_hv,
and hence not calling kvm_arch_vcpu_runnable, we can remove the #ifdef
from kvm_arch_vcpu_runnable.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
This makes arch/powerpc/kvm/book3s_rmhandlers.S and
arch/powerpc/kvm/book3s_hv_rmhandlers.S be assembled as
separate compilation units rather than having them #included in
arch/powerpc/kernel/exceptions-64s.S. We no longer have any
conditional branches between the exception prologs in
exceptions-64s.S and the KVM handlers, so there is no need to
keep their contents close together in the vmlinux image.
In their current location, they are using up part of the limited
space between the first-level interrupt handlers and the firmware
NMI data area at offset 0x7000, and with some kernel configurations
this area will overflow (e.g. allyesconfig), leading to an
"attempt to .org backwards" error when compiling exceptions-64s.S.
Moving them out requires that we add some #includes that the
book3s_{,hv_}rmhandlers.S code was previously getting implicitly
via exceptions-64s.S.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
On a box with gcc 4.3.2, I see errors like:
arch/powerpc/kvm/book3s_hv_rmhandlers.S:1254: Error: Unrecognized opcode: stxvd2x
arch/powerpc/kvm/book3s_hv_rmhandlers.S:1316: Error: Unrecognized opcode: lxvd2x
Signed-off-by: Nishanth Aravamudan <nacc@us.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This adds support for running KVM guests in supervisor mode on those
PPC970 processors that have a usable hypervisor mode. Unfortunately,
Apple G5 machines have supervisor mode disabled (MSR[HV] is forced to
1), but the YDL PowerStation does have a usable hypervisor mode.
There are several differences between the PPC970 and POWER7 in how
guests are managed. These differences are accommodated using the
CPU_FTR_ARCH_201 (PPC970) and CPU_FTR_ARCH_206 (POWER7) CPU feature
bits. Notably, on PPC970:
* The LPCR, LPID or RMOR registers don't exist, and the functions of
those registers are provided by bits in HID4 and one bit in HID0.
* External interrupts can be directed to the hypervisor, but unlike
POWER7 they are masked by MSR[EE] in non-hypervisor modes and use
SRR0/1 not HSRR0/1.
* There is no virtual RMA (VRMA) mode; the guest must use an RMO
(real mode offset) area.
* The TLB entries are not tagged with the LPID, so it is necessary to
flush the whole TLB on partition switch. Furthermore, when switching
partitions we have to ensure that no other CPU is executing the tlbie
or tlbsync instructions in either the old or the new partition,
otherwise undefined behaviour can occur.
* The PMU has 8 counters (PMC registers) rather than 6.
* The DSCR, PURR, SPURR, AMR, AMOR, UAMOR registers don't exist.
* The SLB has 64 entries rather than 32.
* There is no mediated external interrupt facility, so if we switch to
a guest that has a virtual external interrupt pending but the guest
has MSR[EE] = 0, we have to arrange to have an interrupt pending for
it so that we can get control back once it re-enables interrupts. We
do that by sending ourselves an IPI with smp_send_reschedule after
hard-disabling interrupts.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
This adds infrastructure which will be needed to allow book3s_hv KVM to
run on older POWER processors, including PPC970, which don't support
the Virtual Real Mode Area (VRMA) facility, but only the Real Mode
Offset (RMO) facility. These processors require a physically
contiguous, aligned area of memory for each guest. When the guest does
an access in real mode (MMU off), the address is compared against a
limit value, and if it is lower, the address is ORed with an offset
value (from the Real Mode Offset Register (RMOR)) and the result becomes
the real address for the access. The size of the RMA has to be one of
a set of supported values, which usually includes 64MB, 128MB, 256MB
and some larger powers of 2.
Since we are unlikely to be able to allocate 64MB or more of physically
contiguous memory after the kernel has been running for a while, we
allocate a pool of RMAs at boot time using the bootmem allocator. The
size and number of the RMAs can be set using the kvm_rma_size=xx and
kvm_rma_count=xx kernel command line options.
KVM exports a new capability, KVM_CAP_PPC_RMA, to signal the availability
of the pool of preallocated RMAs. The capability value is 1 if the
processor can use an RMA but doesn't require one (because it supports
the VRMA facility), or 2 if the processor requires an RMA for each guest.
This adds a new ioctl, KVM_ALLOCATE_RMA, which allocates an RMA from the
pool and returns a file descriptor which can be used to map the RMA. It
also returns the size of the RMA in the argument structure.
Having an RMA means we will get multiple KMV_SET_USER_MEMORY_REGION
ioctl calls from userspace. To cope with this, we now preallocate the
kvm->arch.ram_pginfo array when the VM is created with a size sufficient
for up to 64GB of guest memory. Subsequently we will get rid of this
array and use memory associated with each memslot instead.
This moves most of the code that translates the user addresses into
host pfns (page frame numbers) out of kvmppc_prepare_vrma up one level
to kvmppc_core_prepare_memory_region. Also, instead of having to look
up the VMA for each page in order to check the page size, we now check
that the pages we get are compound pages of 16MB. However, if we are
adding memory that is mapped to an RMA, we don't bother with calling
get_user_pages_fast and instead just offset from the base pfn for the
RMA.
Typically the RMA gets added after vcpus are created, which makes it
inconvenient to have the LPCR (logical partition control register) value
in the vcpu->arch struct, since the LPCR controls whether the processor
uses RMA or VRMA for the guest. This moves the LPCR value into the
kvm->arch struct and arranges for the MER (mediated external request)
bit, which is the only bit that varies between vcpus, to be set in
assembly code when going into the guest if there is a pending external
interrupt request.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
This lifts the restriction that book3s_hv guests can only run one
hardware thread per core, and allows them to use up to 4 threads
per core on POWER7. The host still has to run single-threaded.
This capability is advertised to qemu through a new KVM_CAP_PPC_SMT
capability. The return value of the ioctl querying this capability
is the number of vcpus per virtual CPU core (vcore), currently 4.
To use this, the host kernel should be booted with all threads
active, and then all the secondary threads should be offlined.
This will put the secondary threads into nap mode. KVM will then
wake them from nap mode and use them for running guest code (while
they are still offline). To wake the secondary threads, we send
them an IPI using a new xics_wake_cpu() function, implemented in
arch/powerpc/sysdev/xics/icp-native.c. In other words, at this stage
we assume that the platform has a XICS interrupt controller and
we are using icp-native.c to drive it. Since the woken thread will
need to acknowledge and clear the IPI, we also export the base
physical address of the XICS registers using kvmppc_set_xics_phys()
for use in the low-level KVM book3s code.
When a vcpu is created, it is assigned to a virtual CPU core.
The vcore number is obtained by dividing the vcpu number by the
number of threads per core in the host. This number is exported
to userspace via the KVM_CAP_PPC_SMT capability. If qemu wishes
to run the guest in single-threaded mode, it should make all vcpu
numbers be multiples of the number of threads per core.
We distinguish three states of a vcpu: runnable (i.e., ready to execute
the guest), blocked (that is, idle), and busy in host. We currently
implement a policy that the vcore can run only when all its threads
are runnable or blocked. This way, if a vcpu needs to execute elsewhere
in the kernel or in qemu, it can do so without being starved of CPU
by the other vcpus.
When a vcore starts to run, it executes in the context of one of the
vcpu threads. The other vcpu threads all go to sleep and stay asleep
until something happens requiring the vcpu thread to return to qemu,
or to wake up to run the vcore (this can happen when another vcpu
thread goes from busy in host state to blocked).
It can happen that a vcpu goes from blocked to runnable state (e.g.
because of an interrupt), and the vcore it belongs to is already
running. In that case it can start to run immediately as long as
the none of the vcpus in the vcore have started to exit the guest.
We send the next free thread in the vcore an IPI to get it to start
to execute the guest. It synchronizes with the other threads via
the vcore->entry_exit_count field to make sure that it doesn't go
into the guest if the other vcpus are exiting by the time that it
is ready to actually enter the guest.
Note that there is no fixed relationship between the hardware thread
number and the vcpu number. Hardware threads are assigned to vcpus
as they become runnable, so we will always use the lower-numbered
hardware threads in preference to higher-numbered threads if not all
the vcpus in the vcore are runnable, regardless of which vcpus are
runnable.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
This improves I/O performance for guests using the PAPR
paravirtualization interface by making the H_PUT_TCE hcall faster, by
implementing it in real mode. H_PUT_TCE is used for updating virtual
IOMMU tables, and is used both for virtual I/O and for real I/O in the
PAPR interface.
Since this moves the IOMMU tables into the kernel, we define a new
KVM_CREATE_SPAPR_TCE ioctl to allow qemu to create the tables. The
ioctl returns a file descriptor which can be used to mmap the newly
created table. The qemu driver models use them in the same way as
userspace managed tables, but they can be updated directly by the
guest with a real-mode H_PUT_TCE implementation, reducing the number
of host/guest context switches during guest IO.
There are certain circumstances where it is useful for userland qemu
to write to the TCE table even if the kernel H_PUT_TCE path is used
most of the time. Specifically, allowing this will avoid awkwardness
when we need to reset the table. More importantly, we will in the
future need to write the table in order to restore its state after a
checkpoint resume or migration.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
This adds the infrastructure for handling PAPR hcalls in the kernel,
either early in the guest exit path while we are still in real mode,
or later once the MMU has been turned back on and we are in the full
kernel context. The advantage of handling hcalls in real mode if
possible is that we avoid two partition switches -- and this will
become more important when we support SMT4 guests, since a partition
switch means we have to pull all of the threads in the core out of
the guest. The disadvantage is that we can only access the kernel
linear mapping, not anything vmalloced or ioremapped, since the MMU
is off.
This also adds code to handle the following hcalls in real mode:
H_ENTER Add an HPTE to the hashed page table
H_REMOVE Remove an HPTE from the hashed page table
H_READ Read HPTEs from the hashed page table
H_PROTECT Change the protection bits in an HPTE
H_BULK_REMOVE Remove up to 4 HPTEs from the hashed page table
H_SET_DABR Set the data address breakpoint register
Plus code to handle the following hcalls in the kernel:
H_CEDE Idle the vcpu until an interrupt or H_PROD hcall arrives
H_PROD Wake up a ceded vcpu
H_REGISTER_VPA Register a virtual processor area (VPA)
The code that runs in real mode has to be in the base kernel, not in
the module, if KVM is compiled as a module. The real-mode code can
only access the kernel linear mapping, not vmalloc or ioremap space.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
This adds support for KVM running on 64-bit Book 3S processors,
specifically POWER7, in hypervisor mode. Using hypervisor mode means
that the guest can use the processor's supervisor mode. That means
that the guest can execute privileged instructions and access privileged
registers itself without trapping to the host. This gives excellent
performance, but does mean that KVM cannot emulate a processor
architecture other than the one that the hardware implements.
This code assumes that the guest is running paravirtualized using the
PAPR (Power Architecture Platform Requirements) interface, which is the
interface that IBM's PowerVM hypervisor uses. That means that existing
Linux distributions that run on IBM pSeries machines will also run
under KVM without modification. In order to communicate the PAPR
hypercalls to qemu, this adds a new KVM_EXIT_PAPR_HCALL exit code
to include/linux/kvm.h.
Currently the choice between book3s_hv support and book3s_pr support
(i.e. the existing code, which runs the guest in user mode) has to be
made at kernel configuration time, so a given kernel binary can only
do one or the other.
This new book3s_hv code doesn't support MMIO emulation at present.
Since we are running paravirtualized guests, this isn't a serious
restriction.
With the guest running in supervisor mode, most exceptions go straight
to the guest. We will never get data or instruction storage or segment
interrupts, alignment interrupts, decrementer interrupts, program
interrupts, single-step interrupts, etc., coming to the hypervisor from
the guest. Therefore this introduces a new KVMTEST_NONHV macro for the
exception entry path so that we don't have to do the KVM test on entry
to those exception handlers.
We do however get hypervisor decrementer, hypervisor data storage,
hypervisor instruction storage, and hypervisor emulation assist
interrupts, so we have to handle those.
In hypervisor mode, real-mode accesses can access all of RAM, not just
a limited amount. Therefore we put all the guest state in the vcpu.arch
and use the shadow_vcpu in the PACA only for temporary scratch space.
We allocate the vcpu with kzalloc rather than vzalloc, and we don't use
anything in the kvmppc_vcpu_book3s struct, so we don't allocate it.
We don't have a shared page with the guest, but we still need a
kvm_vcpu_arch_shared struct to store the values of various registers,
so we include one in the vcpu_arch struct.
The POWER7 processor has a restriction that all threads in a core have
to be in the same partition. MMU-on kernel code counts as a partition
(partition 0), so we have to do a partition switch on every entry to and
exit from the guest. At present we require the host and guest to run
in single-thread mode because of this hardware restriction.
This code allocates a hashed page table for the guest and initializes
it with HPTEs for the guest's Virtual Real Memory Area (VRMA). We
require that the guest memory is allocated using 16MB huge pages, in
order to simplify the low-level memory management. This also means that
we can get away without tracking paging activity in the host for now,
since huge pages can't be paged or swapped.
This also adds a few new exports needed by the book3s_hv code.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
Paul Mackerras