I noticed ksm spending quite a lot of time in memcmp on a large
KVM box. The current memcmp loop is very unoptimised - byte at a
time compares with no loop unrolling. We can do much much better.
Optimise the loop in a few ways:
- Unroll the byte at a time loop
- For large (at least 32 byte) comparisons that are also 8 byte
aligned, use an unrolled modulo scheduled loop using 8 byte
loads. This is similar to our glibc memcmp.
A simple microbenchmark testing 10000000 iterations of an 8192 byte
memcmp was used to measure the performance:
baseline: 29.93 s
modified: 1.70 s
Just over 17x faster.
v2: Incorporated some suggestions from Segher:
- Use andi. instead of rdlicl.
- Convert bdnzt eq, to bdnz. It's just duplicating the earlier compare
and was a relic from a previous version.
- Don't use cr5, we have plans to use that CR field for fast local
atomics.
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
In the Makefile, string.o (which is generated from string.S) is
included into the list of objects being built unconditionally
(obj-y) in line 12.
Additionally, if CONFIG_PPC64 is set, it is included again in
line 17.
This patch removes the latter unnecessary inclusion.
Signed-off-by: Andreas Ruprecht <rupran@einserver.de>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Although we are now selecting NO_BOOTMEM, we still have some traces of
bootmem lying around. That is because even with NO_BOOTMEM there is
still a shim that converts bootmem calls into memblock calls, but
ultimately we want to remove all traces of bootmem.
Most of the patch is conversions from alloc_bootmem() to
memblock_virt_alloc(). In general a call such as:
p = (struct foo *)alloc_bootmem(x);
Becomes:
p = memblock_virt_alloc(x, 0);
We don't need the cast because memblock_virt_alloc() returns a void *.
The alignment value of zero tells memblock to use the default alignment,
which is SMP_CACHE_BYTES, the same value alloc_bootmem() uses.
We remove a number of NULL checks on the result of
memblock_virt_alloc(). That is because memblock_virt_alloc() will panic
if it can't allocate, in exactly the same way as alloc_bootmem(), so the
NULL checks are and always have been redundant.
The memory returned by memblock_virt_alloc() is already zeroed, so we
remove several memsets of the result of memblock_virt_alloc().
Finally we convert a few uses of __alloc_bootmem(x, y, MAX_DMA_ADDRESS)
to just plain memblock_virt_alloc(). We don't use memblock_alloc_base()
because MAX_DMA_ADDRESS is ~0ul on powerpc, so limiting the allocation
to that is pointless, 16XB ought to be enough for anyone.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Commit be96f63375 ("powerpc: Split out instruction analysis
part of emulate_step()") added some calls to do_fp_load()
and do_fp_store(), which fail to compile on configs with
CONFIG_PPC_FPU=n and CONFIG_PPC_EMULATE_SSTEP=y. This fixes
the compile by adding #ifdef CONFIG_PPC_FPU around the code
that calls these functions.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Added in 2008, but has never had any in-tree users, and no other
architectures provide it.
Signed-off-by: Kyle McMartin <kyle@redhat.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
The size field of the op.type word is now the total number of bytes
to be loaded or stored.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This extends the instruction emulation done by analyse_instr() and
emulate_step() to handle a few more instructions that are found in
the kernel.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This splits out the instruction analysis part of emulate_step() into
a separate analyse_instr() function, which decodes the instruction,
but doesn't execute any load or store instructions. It does execute
integer instructions and branches which can be executed purely by
updating register values in the pt_regs struct. For other instructions,
it returns the instruction type and other details in a new
instruction_op struct. emulate_step() then uses that information
to execute loads, stores, cache operations, mfmsr, mtmsr[d], and
(on 64-bit) sc instructions.
The reason for doing this is so that the KVM code can use it instead
of having its own separate instruction emulation code. Possibly the
alignment interrupt handler could also use this.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Move the lib symbol exports closer to their function definitions
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Similar to the previous commit which described why we need to add a
barrier to arch_spin_is_locked(), we have a similar problem with
spin_unlock_wait().
We need a barrier on entry to ensure any spinlock we have previously
taken is visibly locked prior to the load of lock->slock.
It's also not clear if spin_unlock_wait() is intended to have ACQUIRE
semantics. For now be conservative and add a barrier on exit to give it
ACQUIRE semantics.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
There are still a few occurences where it remains, because it helps to
explain something that persists.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
memmove may be called from module code copy_pages(btrfs), and it may
call memcpy, which may call back to C code, so it needs to use
_GLOBAL_TOC to set up r2 correctly.
This fixes following error when I tried to boot an le guest:
Vector: 300 (Data Access) at [c000000073f97210]
pc: c000000000015004: enable_kernel_altivec+0x24/0x80
lr: c000000000058fbc: enter_vmx_copy+0x3c/0x60
sp: c000000073f97490
msr: 8000000002009033
dar: d000000001d50170
dsisr: 40000000
current = 0xc0000000734c0000
paca = 0xc00000000fff0000 softe: 0 irq_happened: 0x01
pid = 815, comm = mktemp
enter ? for help
[c000000073f974f0] c000000000058fbc enter_vmx_copy+0x3c/0x60
[c000000073f97510] c000000000057d34 memcpy_power7+0x274/0x840
[c000000073f97610] d000000001c3179c copy_pages+0xfc/0x110 [btrfs]
[c000000073f97660] d000000001c3c248 memcpy_extent_buffer+0xe8/0x160 [btrfs]
[c000000073f97700] d000000001be4be8 setup_items_for_insert+0x208/0x4a0 [btrfs]
[c000000073f97820] d000000001be50b4 btrfs_insert_empty_items+0xf4/0x140 [btrfs]
[c000000073f97890] d000000001bfed30 insert_with_overflow+0x70/0x180 [btrfs]
[c000000073f97900] d000000001bff174 btrfs_insert_dir_item+0x114/0x2f0 [btrfs]
[c000000073f979a0] d000000001c1f92c btrfs_add_link+0x10c/0x370 [btrfs]
[c000000073f97a40] d000000001c20e94 btrfs_create+0x204/0x270 [btrfs]
[c000000073f97b00] c00000000026d438 vfs_create+0x178/0x210
[c000000073f97b50] c000000000270a70 do_last+0x9f0/0xe90
[c000000073f97c20] c000000000271010 path_openat+0x100/0x810
[c000000073f97ce0] c000000000272ea8 do_filp_open+0x58/0xd0
[c000000073f97dc0] c00000000025ade8 do_sys_open+0x1b8/0x300
[c000000073f97e30] c00000000000a008 syscall_exit+0x0/0x7c
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This fixes some bugs in emulate_step(). First, the setting of the carry
bit for the arithmetic right-shift instructions was not correct on 64-bit
machines because we were masking with a mask of type int rather than
unsigned long. Secondly, the sld (shift left doubleword) instruction was
using the wrong instruction field for the register containing the shift
count.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Commit cd64d1697c ("powerpc: mtmsrd not defined") added a check for
CONFIG_PPC_CPU were a check for CONFIG_PPC_FPU was clearly intended.
Fixes: cd64d1697c ("powerpc: mtmsrd not defined")
Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
__clear_user and copy_page load from the TOC and are also exported
to modules. This means we have to use _GLOBAL_TOC() so that we
create the global entry point that sets up the TOC.
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This series adds support for building the powerpc 64-bit
LE kernel using the new ABI v2. We already supported
running ABI v2 userspace programs but this adds support
for building the kernel itself using the new ABI.
Unaligned stores take alignment exceptions on POWER7 running in little-endian.
This is a dumb little-endian base memcpy that prevents unaligned stores.
Once booted the feature fixup code switches over to the VMX copy loops
(which are already endian safe).
The question is what we do before that switch over. The base 64bit
memcpy takes alignment exceptions on POWER7 so we can't use it as is.
Fixing the causes of alignment exception would slow it down, because
we'd need to ensure all loads and stores are aligned either through
rotate tricks or bytewise loads and stores. Either would be bad for
all other 64bit platforms.
[ I simplified the loop a bit - Anton ]
Signed-off-by: Philippe Bergheaud <felix@linux.vnet.ibm.com>
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
If an assembly function that calls back into c code is exported to
modules, we need to ensure r2 is setup correctly. There are only
two places crazy enough to do it (two of which are my fault).
Signed-off-by: Anton Blanchard <anton@samba.org>
Some of the assembler files in lib/ make use of the fact that in the
ELFv1 ABI, the caller guarantees to provide stack space to save the
parameter registers r3 ... r10. This guarantee is no longer present
in ELFv2 for functions that have no variable argument list and no
more than 8 arguments.
Change the affected routines to temporarily store registers in the
red zone and/or the top of their own stack frame (in the space
provided to save r31 .. r29, which is actually not used in these
routines).
In opal_query_takeover, simply always allocate a stack frame;
the routine is not performance critical.
Signed-off-by: Ulrich Weigand <ulrich.weigand@de.ibm.com>
Signed-off-by: Anton Blanchard <anton@samba.org>
binutils is smart enough to know that a branch to a function
descriptor is actually a branch to the functions text address.
Alan tells me that binutils has been doing this for 9 years.
Signed-off-by: Anton Blanchard <anton@samba.org>
Turn Anton's memcpy / copy_tofrom_user test into something that can
live in tools/testing/selftests.
It requires one turd in arch/powerpc/lib/memcpy_64.S, but it's pretty
harmless IMHO.
We are sailing very close to the wind with the feature macros. We define
them to nothing, which currently means we get a few extra nops and
include the unaligned calls.
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
GCC 4.8 now generates out-of-line vr save/restore functions when
optimizing for size. They are needed for the raid6 altivec support.
Signed-off-by: Andreas Schwab <schwab@linux-m68k.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Merge a pile of fixes that went into the "merge" branch (3.13-rc's) such
as Anton Little Endian fixes.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
The powerpc 64-bit __copy_tofrom_user() function uses shifts to handle
unaligned invocations. However, these shifts were designed for
big-endian systems: On little-endian systems, they must shift in the
opposite direction.
This commit relies on the C preprocessor to insert the correct shifts
into the assembly code.
[ This is a rare but nasty LE issue. Most of the time we use the POWER7
optimised __copy_tofrom_user_power7 loop, but when it hits an exception
we fall back to the base __copy_tofrom_user loop. - Anton ]
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
So that it can be used by other codes. No function change.
Signed-off-by: Kevin Hao <haokexin@gmail.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Add a VMX optimised xor, used primarily for RAID5. On a POWER7 blade
this is a decent win:
32regs : 17932.800 MB/sec
altivec : 19724.800 MB/sec
The bigger gain is when the same test is run in SMT4 mode, as it
would if there was a lot of work going on:
8regs : 8377.600 MB/sec
altivec : 15801.600 MB/sec
I tested this against an array created without the patch, and also
verified it worked as expected on a little endian kernel.
[ Fix !CONFIG_ALTIVEC build -- BenH ]
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This patch addresses unaligned single precision floating point loads
and stores in the single-step code. The old implementation
improperly treated an 8 byte structure as an array of two 4 byte
words, which is a classic little endian bug.
Signed-off-by: Tom Musta <tmusta@gmail.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This patch modifies the unaligned access routines of the sstep.c
module so that it properly reverses the bytes of storage operands
in the little endian kernel kernel. This is implemented by
breaking an unaligned little endian access into a combination of
single byte accesses plus an overal byte reversal operation.
Signed-off-by: Tom Musta <tmusta@gmail.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
We need to fix some endian issues in our memcpy code. For now
just enable the generic memcpy routine for little endian builds.
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
We need to fix some endian issues in our checksum code. For now
just enable the generic checksum routines for little endian builds.
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Fix the permute loops for little endian.
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
The csum_partial_copy_generic() function saves the PowerPC non-volatile
r14, r15, and r16 registers for the main checksum-and-copy loop.
Unfortunately, it fails to restore them upon error exit from this loop,
which results in silent corruption of these registers in the presumably
rare event of an access exception within that loop.
This commit therefore restores these register on error exit from the loop.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Anton Blanchard <anton@samba.org>
Cc: stable@vger.kernel.org
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
The csum_partial_copy_generic() uses register r7 to adjust the remaining
bytes to process. Unfortunately, r7 also holds a parameter, namely the
address of the flag to set in case of access exceptions while reading
the source buffer. Lacking a quantum implementation of PowerPC, this
commit instead uses register r9 to do the adjusting, leaving r7's
pointer uncorrupted.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Anton Blanchard <anton@samba.org>
Cc: stable@vger.kernel.org
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
We've been keeping that field in thread_struct for a while, it contains
the "limit" of the current stack pointer and is meant to be used for
detecting stack overflows.
It has a few problems however:
- First, it was never actually *used* on 64-bit. Set and updated but
not actually exploited
- When switching stack to/from irq and softirq stacks, it's update
is racy unless we hard disable interrupts, which is costly. This
is fine on 32-bit as we don't soft-disable there but not on 64-bit.
Thus rather than fixing 2 in order to implement 1 in some hypothetical
future, let's remove the code completely from 64-bit. In order to avoid
a clutter of ifdef's, we remove the updates from C code completely
during interrupt stack switching, and instead maintain it from the
asm helper that is used to do the stack switching in the first place.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
The stmw instruction was incorrectly decoded as an update form instruction
and thus the RA register was being clobbered.
Also, the utility routine to write memory to unaligned addresses breaks the
operation into smaller aligned accesses but was incorrectly incrementing
the address by only one; it needs to increment the address by the size of
the smaller aligned chunk.
Signed-off-by: Tom Musta <tmusta@us.ibm.com>
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>
Check truncate_if_32bit() on final write to nip.
Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
No code changes, just documenting what's happening a little better.
Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Uprobes uses emulate_step in sstep.c, but we haven't explicitly specified
the dependency. On pseries HAVE_HW_BREAKPOINT protects us, but 44x has no
such luxury.
Consolidate other users that depend on sstep and create a new config option.
Signed-off-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Signed-off-by: Suzuki K. Poulose <suzuki@in.ibm.com>
Cc: linuxppc-dev@ozlabs.org
Cc: stable@vger.kernel.org
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Finally remove the two level TOC and build with -mcmodel=medium.
Unfortunately we can't build modules with -mcmodel=medium due to
the tricks the kernel module loader plays with percpu data:
# -mcmodel=medium breaks modules because it uses 32bit offsets from
# the TOC pointer to create pointers where possible. Pointers into the
# percpu data area are created by this method.
#
# The kernel module loader relocates the percpu data section from the
# original location (starting with 0xd...) to somewhere in the base
# kernel percpu data space (starting with 0xc...). We need a full
# 64bit relocation for this to work, hence -mcmodel=large.
On older kernels we fall back to the two level TOC (-mminimal-toc)
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
We don't do the real store operation for kprobing 'stwu Rx,(y)R1'
since this may corrupt the exception frame, now we will do this
operation safely in exception return code after migrate current
exception frame below the kprobed function stack.
So we only update gpr[1] here and trigger a thread flag to mask
this.
Note we should make sure if we trigger kernel stack over flow.
Signed-off-by: Tiejun Chen <tiejun.chen@windriver.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
patch_instruction() can be called very early on ppc32, when the kernel
isn't yet running at it's linked address. That can cause the !
is_kernel_addr() test in __put_user() to trip and call might_sleep()
which is very bad at that point during boot.
Use a lower level function instead for now, at least until we get to
rework ppc32 boot process to do the code patching later, like ppc64
does.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Michael Ellerman