Commit Graph

56 Commits

Author SHA1 Message Date
Marcelo Tosatti a6085fbaf6 KVM: MMU: bail out pagewalk on kvm_read_guest error
Exit the guest pagetable walk loop if reading gpte failed. Otherwise its
possible to enter an endless loop processing the previous present pte.

Cc: stable@kernel.org
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
2010-01-25 12:26:38 -02:00
Marcelo Tosatti fb341f572d KVM: MMU: remove prefault from invlpg handler
The invlpg prefault optimization breaks Windows 2008 R2 occasionally.

The visible effect is that the invlpg handler instantiates a pte which
is, microseconds later, written with a different gfn by another vcpu.

The OS could have other mechanisms to prevent a present translation from
being used, which the hypervisor is unaware of.

While the documentation states that the cpu is at liberty to prefetch tlb
entries, it looks like this is not heeded, so remove tlb prefetch from
invlpg.

Cc: stable@kernel.org
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
2009-12-27 13:36:30 -02:00
Marcelo Tosatti 5f5c35aad5 KVM: MMU: update invlpg handler comment
Large page translations are always synchronized (either in level 3
or level 2), so its not necessary to properly deal with them
in the invlpg handler.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
2009-12-03 09:32:23 +02:00
Izik Eidus 1403283acc KVM: MMU: add SPTE_HOST_WRITEABLE flag to the shadow ptes
this flag notify that the host physical page we are pointing to from
the spte is write protected, and therefore we cant change its access
to be write unless we run get_user_pages(write = 1).

(this is needed for change_pte support in kvm)

Signed-off-by: Izik Eidus <ieidus@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
2009-10-04 17:04:50 +02:00
Joerg Roedel 7e4e4056f7 KVM: MMU: shadow support for 1gb pages
This patch adds support for shadow paging to the 1gb page table code in KVM.
With this code the guest can use 1gb pages even if the host does not support
them.

[ Marcelo: fix shadow page collision on pmd level if a guest 1gb page is mapped
           with 4kb ptes on host level ]

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
2009-09-10 08:33:19 +03:00
Joerg Roedel e04da980c3 KVM: MMU: make page walker aware of mapping levels
The page walker may be used with nested paging too when accessing mmio
areas.  Make it support the additional page-level too.

[ Marcelo: fix reserved bit check for 1gb pte ]

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
2009-09-10 08:33:18 +03:00
Joerg Roedel 852e3c19ac KVM: MMU: make direct mapping paths aware of mapping levels
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
2009-09-10 08:33:18 +03:00
Joerg Roedel d25797b24c KVM: MMU: rename is_largepage_backed to mapping_level
With the new name and the corresponding backend changes this function
can now support multiple hugepage sizes.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
2009-09-10 08:33:18 +03:00
Avi Kivity 0742017159 KVM: MMU: Trace guest pagetable walker
Signed-off-by: Avi Kivity <avi@redhat.com>
2009-09-10 08:33:09 +03:00
Joerg Roedel ec04b2604c KVM: Prepare memslot data structures for multiple hugepage sizes
[avi: fix build on non-x86]

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
2009-09-10 08:33:02 +03:00
Avi Kivity d555c333aa KVM: MMU: s/shadow_pte/spte/
We use shadow_pte and spte inconsistently, switch to the shorter spelling.

Rename set_shadow_pte() to __set_spte() to avoid a conflict with the
existing set_spte(), and to indicate its lowlevelness.

Signed-off-by: Avi Kivity <avi@redhat.com>
2009-09-10 08:32:51 +03:00
Avi Kivity 43a3795a3a KVM: MMU: Adjust pte accessors to explicitly indicate guest or shadow pte
Since the guest and host ptes can have wildly different format, adjust
the pte accessor names to indicate on which type of pte they operate on.

No functional changes.

Signed-off-by: Avi Kivity <avi@redhat.com>
2009-09-10 08:32:51 +03:00
Avi Kivity 6de4f3ada4 KVM: Cache pdptrs
Instead of reloading the pdptrs on every entry and exit (vmcs writes on vmx,
guest memory access on svm) extract them on demand.

Signed-off-by: Avi Kivity <avi@redhat.com>
2009-09-10 08:32:46 +03:00
Jaswinder Singh Rajput bde8922325 KVM: shut up uninit compiler warning in paging_tmpl.h
Dixes compilation warning:
  CC      arch/x86/kernel/io_delay.o
 arch/x86/kvm/paging_tmpl.h: In function ‘paging64_fetch’:
 arch/x86/kvm/paging_tmpl.h:279: warning: ‘sptep’ may be used uninitialized in this function
 arch/x86/kvm/paging_tmpl.h: In function ‘paging32_fetch’:
 arch/x86/kvm/paging_tmpl.h:279: warning: ‘sptep’ may be used uninitialized in this function

warning is bogus (always have a least one level), but need to shut the compiler
up.

Signed-off-by: Jaswinder Singh Rajput <jaswinderrajput@gmail.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
2009-06-28 14:10:32 +03:00
Marcelo Tosatti c2d0ee46e6 KVM: MMU: remove global page optimization logic
Complexity to fix it not worthwhile the gains, as discussed
in http://article.gmane.org/gmane.comp.emulators.kvm.devel/28649.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
2009-06-10 11:48:39 +03:00
Dong, Eddie 82725b20e2 KVM: MMU: Emulate #PF error code of reserved bits violation
Detect, indicate, and propagate page faults where reserved bits are set.
Take care to handle the different paging modes, each of which has different
sets of reserved bits.

[avi: fix pte reserved bits for efer.nxe=0]

Signed-off-by: Eddie Dong <eddie.dong@intel.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
2009-06-10 11:48:35 +03:00
Eddie Dong a8b876b1a4 KVM: MMU: Fix comment in page_fault()
The original one is for the code before refactoring.

Signed-off-by: Yaozu (Eddie) Dong <eddie.dong@intel.com>
Signed-off-by: Sheng Yang <sheng@linux.intel.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
2009-06-10 11:48:34 +03:00
Joerg Roedel f5a1e9f895 KVM: MMU: remove call to kvm_mmu_pte_write from walk_addr
There is no reason to update the shadow pte here because the guest pte
is only changed to dirty state.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
2009-06-10 11:48:26 +03:00
Andrea Arcangeli 4539b35881 KVM: Fix missing smp tlb flush in invlpg
When kvm emulates an invlpg instruction, it can drop a shadow pte, but
leaves the guest tlbs intact.  This can cause memory corruption when
swapping out.

Without this the other cpu can still write to a freed host physical page.
tlb smp flush must happen if rmap_remove is called always before mmu_lock
is released because the VM will take the mmu_lock before it can finally add
the page to the freelist after swapout. mmu notifier makes it safe to flush
the tlb after freeing the page (otherwise it would never be safe) so we can do
a single flush for multiple sptes invalidated.

Cc: stable@kernel.org
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
2009-03-24 11:03:14 +02:00
Joerg Roedel c5bc224240 KVM: MMU: Fix another largepage memory leak
In the paging_fetch function rmap_remove is called after setting a large
pte to non-present. This causes rmap_remove to not drop the reference to
the large page. The result is a memory leak of that page.

Cc: stable@kernel.org
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Acked-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
2009-03-24 11:03:11 +02:00
Avi Kivity f6e2c02b6d KVM: MMU: Rename "metaphysical" attribute to "direct"
This actually describes what is going on, rather than alerting the reader
that something strange is going on.

Signed-off-by: Avi Kivity <avi@redhat.com>
2009-03-24 11:03:04 +02:00
Avi Kivity a461930bc3 KVM: MMU: Replace walk_shadow() by for_each_shadow_entry() in invlpg()
Signed-off-by: Avi Kivity <avi@redhat.com>
2009-03-24 11:02:53 +02:00
Avi Kivity e7a04c99b5 KVM: MMU: Replace walk_shadow() by for_each_shadow_entry() in fetch()
Effectively reverting to the pre walk_shadow() version -- but now
with the reusable for_each().

Signed-off-by: Avi Kivity <avi@redhat.com>
2009-03-24 11:02:52 +02:00
Marcelo Tosatti 8791723920 KVM: MMU: handle large host sptes on invlpg/resync
The invlpg and sync walkers lack knowledge of large host sptes,
descending to non-existant pagetable level.

Stop at directory level in such case.

Fixes SMP Windows XP with hugepages.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
2008-12-31 16:55:49 +02:00
Marcelo Tosatti ad218f85e3 KVM: MMU: prepopulate the shadow on invlpg
If the guest executes invlpg, peek into the pagetable and attempt to
prepopulate the shadow entry.

Also stop dirty fault updates from interfering with the fork detector.

2% improvement on RHEL3/AIM7.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
2008-12-31 16:55:44 +02:00
Marcelo Tosatti 6cffe8ca4a KVM: MMU: skip global pgtables on sync due to cr3 switch
Skip syncing global pages on cr3 switch (but not on cr4/cr0). This is
important for Linux 32-bit guests with PAE, where the kmap page is
marked as global.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
2008-12-31 16:55:44 +02:00
Marcelo Tosatti 6c475352e8 KVM: MMU: avoid creation of unreachable pages in the shadow
It is possible for a shadow page to have a parent link
pointing to a freed page. When zapping a high level table,
kvm_mmu_page_unlink_children fails to remove the parent_pte link.
For that to happen, the child must be unreachable via the shadow
tree, which can happen in shadow_walk_entry if the guest pte was
modified in between walk() and fetch(). Remove the parent pte
reference in such case.

Possible cause for oops in bug #2217430.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
2008-11-26 12:34:27 +02:00
Marcelo Tosatti 4731d4c7a0 KVM: MMU: out of sync shadow core
Allow guest pagetables to go out of sync.  Instead of emulating write
accesses to guest pagetables, or unshadowing them, we un-write-protect
the page table and allow the guest to modify it at will.  We rely on
invlpg executions to synchronize individual ptes, and will synchronize
the entire pagetable on tlb flushes.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
2008-10-15 14:25:25 +02:00
Marcelo Tosatti a7052897b3 KVM: x86: trap invlpg
With pages out of sync invlpg needs to be trapped. For now simply nuke
the entry.

Untested on AMD.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
2008-10-15 14:25:21 +02:00
Marcelo Tosatti e8bc217aef KVM: MMU: mode specific sync_page
Examine guest pagetable and bring the shadow back in sync. Caller is responsible
for local TLB flush before re-entering guest mode.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
2008-10-15 14:25:19 +02:00
Marcelo Tosatti 93a423e704 KVM: MMU: flush remote TLBs on large->normal entry overwrite
It is necessary to flush all TLB's when a large spte entry is
overwritten with a normal page directory pointer.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
2008-10-15 14:25:15 +02:00
Marcelo Tosatti 4c2155ce81 KVM: switch to get_user_pages_fast
Convert gfn_to_pfn to use get_user_pages_fast, which can do lockless
pagetable lookups on x86. Kernel compilation on 4-way guest is 3.7%
faster on VMX.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
2008-10-15 14:25:06 +02:00
Sheng Yang d40a1ee485 KVM: MMU: Modify kvm_shadow_walk.entry to accept u64 addr
EPT is 4 level by default in 32pae(48 bits), but the addr parameter
of kvm_shadow_walk->entry() only accept unsigned long as virtual
address, which is 32bit in 32pae. This result in SHADOW_PT_INDEX()
overflow when try to fetch level 4 index.

Fix it by extend kvm_shadow_walk->entry() to accept 64bit addr in
parameter.

Signed-off-by: Sheng Yang <sheng.yang@intel.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-10-15 10:15:25 +02:00
Avi Kivity abb9e0b8e3 KVM: MMU: Convert the paging mode shadow walk to use the generic walker
Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-10-15 10:15:23 +02:00
Avi Kivity 135f8c2b07 KVM: MMU: Move SHADOW_PT_INDEX to mmu.c
It is not specific to the paging mode, so can be made global (and reusable).

Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-10-15 10:15:22 +02:00
Avi Kivity cd5998ebfb KVM: MMU: Fix torn shadow pte
The shadow code assigns a pte directly in one place, which is nonatomic on
i386 can can cause random memory references.  Fix by using an atomic setter.

Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-08-25 17:24:27 +03:00
Andrea Arcangeli e930bffe95 KVM: Synchronize guest physical memory map to host virtual memory map
Synchronize changes to host virtual addresses which are part of
a KVM memory slot to the KVM shadow mmu.  This allows pte operations
like swapping, page migration, and madvise() to transparently work
with KVM.

Signed-off-by: Andrea Arcangeli <andrea@qumranet.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-07-29 12:33:53 +03:00
Avi Kivity eab9f71feb KVM: MMU: Optimize prefetch_page()
Instead of reading each pte individually, read 256 bytes worth of ptes and
batch process them.

Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-07-20 12:42:28 +03:00
Avi Kivity ebb0e6264c KVM: MMU: Fix printk() format string
Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-06-06 21:36:20 +03:00
Anthony Liguori 35149e2129 KVM: MMU: Don't assume struct page for x86
This patch introduces a gfn_to_pfn() function and corresponding functions like
kvm_release_pfn_dirty().  Using these new functions, we can modify the x86
MMU to no longer assume that it can always get a struct page for any given gfn.

We don't want to eliminate gfn_to_page() entirely because a number of places
assume they can do gfn_to_page() and then kmap() the results.  When we support
IO memory, gfn_to_page() will fail for IO pages although gfn_to_pfn() will
succeed.

This does not implement support for avoiding reference counting for reserved
RAM or for IO memory.  However, it should make those things pretty straight
forward.

Since we're only introducing new common symbols, I don't think it will break
the non-x86 architectures but I haven't tested those.  I've tested Intel,
AMD, NPT, and hugetlbfs with Windows and Linux guests.

[avi: fix overflow when shifting left pfns by adding casts]

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-04-27 12:01:15 +03:00
Marcelo Tosatti 3200f405a1 KVM: MMU: unify slots_lock usage
Unify slots_lock acquision around vcpu_run(). This is simpler and less
error-prone.

Also fix some callsites that were not grabbing the lock properly.

[avi: drop slots_lock while in guest mode to avoid holding the lock
      for indefinite periods]

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-04-27 12:00:52 +03:00
Avi Kivity 947da53830 KVM: MMU: Set the accessed bit on non-speculative shadow ptes
If we populate a shadow pte due to a fault (and not speculatively due to a
pte write) then we can set the accessed bit on it, as we know it will be
set immediately on the next guest instruction.  This saves a read-modify-write
operation.

Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-04-27 12:00:33 +03:00
Harvey Harrison b8688d51bb KVM: replace remaining __FUNCTION__ occurances
__FUNCTION__ is gcc-specific, use __func__

Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-04-27 11:53:27 +03:00
Marcelo Tosatti 05da45583d KVM: MMU: large page support
Create large pages mappings if the guest PTE's are marked as such and
the underlying memory is hugetlbfs backed.  If the largepage contains
write-protected pages, a large pte is not used.

Gives a consistent 2% improvement for data copies on ram mounted
filesystem, without NPT/EPT.

Anthony measures a 4% improvement on 4-way kernbench, with NPT.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-04-27 11:53:25 +03:00
Avi Kivity d196e34336 KVM: MMU: Decouple mmio from shadow page tables
Currently an mmio guest pte is encoded in the shadow pagetable as a
not-present trapping pte, with the SHADOW_IO_MARK bit set.  However
nothing is ever done with this information, so maintaining it is a
useless complication.

This patch moves the check for mmio to before shadow ptes are instantiated,
so the shadow code is never invoked for ptes that reference mmio.  The code
is simpler, and with future work, can be made to handle mmio concurrently.

Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-04-27 11:53:17 +03:00
Dong, Eddie 489f1d6526 KVM: MMU: Update shadow ptes on partial guest pte writes
A guest partial guest pte write will leave shadow_trap_nonpresent_pte
in spte, which generates a vmexit at the next guest access through that pte.

This patch improves this by reading the full guest pte in advance and thus
being able to update the spte and eliminate the vmexit.

This helps pae guests which use two 32-bit writes to set a single 64-bit pte.

[truncation fix by Eric]

Signed-off-by: Yaozu (Eddie) Dong <eddie.dong@intel.com>
Signed-off-by: Feng (Eric) Liu <eric.e.liu@intel.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-04-27 11:53:13 +03:00
Avi Kivity f7d9c7b7b9 KVM: MMU: Fix race when instantiating a shadow pte
For improved concurrency, the guest walk is performed concurrently with other
vcpus.  This means that we need to revalidate the guest ptes once we have
write-protected the guest page tables, at which point they can no longer be
modified.

The current code attempts to avoid this check if the shadow page table is not
new, on the assumption that if it has existed before, the guest could not have
modified the pte without the shadow lock.  However the assumption is incorrect,
as the racing vcpu could have modified the pte, then instantiated the shadow
page, before our vcpu regains control:

  vcpu0        vcpu1

  fault
  walk pte

               modify pte
               fault in same pagetable
               instantiate shadow page

  lookup shadow page
  conclude it is old
  instantiate spte based on stale guest pte

We could do something clever with generation counters, but a test run by
Marcelo suggests this is unnecessary and we can just do the revalidation
unconditionally.  The pte will be in the processor cache and the check can
be quite fast.

Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-03-04 15:19:49 +02:00
Marcelo Tosatti 24993d5349 KVM: make MMU_DEBUG compile again
the cr3 variable is now inside the vcpu->arch structure.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-03-04 15:19:47 +02:00
Izik Eidus 72dc67a696 KVM: remove the usage of the mmap_sem for the protection of the memory slots.
This patch replaces the mmap_sem lock for the memory slots with a new
kvm private lock, it is needed beacuse untill now there were cases where
kvm accesses user memory while holding the mmap semaphore.

Signed-off-by: Izik Eidus <izike@qumranet.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-03-04 15:19:40 +02:00
Dong, Eddie 5882842f9b KVM: MMU: Merge shadow level check in FNAME(fetch)
Remove the redundant level check when fetching
shadow pte for present & non-present spte.

Signed-off-by: Yaozu (Eddie) Dong <eddie.dong@intel.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-01-30 18:01:21 +02:00