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Groups > linux.kernel > #1738005
| From | Ingo Molnar <mingo@kernel.org> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | [PATCH 31/33] x86/fpu: Simplify and speed up fpu__copy() |
| Date | 2017-09-23 15:10 +0200 |
| Message-ID | <usSlY-3wU-21@gated-at.bofh.it> (permalink) |
| References | <usSlX-3wU-3@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
fpu__copy() has a preempt_disable()/enable() pair, which it had to do to
be able to atomically unlazy the current task when doing an FNSAVE.
But we don't unlazy tasks anymore, we always do direct saves/restores of
FPU context.
So remove both the unnecessary critical section, and update the comments.
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Eric Biggers <ebiggers3@gmail.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/kernel/fpu/core.c | 15 +++------------
1 file changed, 3 insertions(+), 12 deletions(-)
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index 4acfc0ebc160..e935f8faf287 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -206,22 +206,13 @@ int fpu__copy(struct fpu *dst_fpu, struct fpu *src_fpu)
* Save current FPU registers directly into the child
* FPU context, without any memory-to-memory copying.
*
- * We have to do all this with preemption disabled,
- * mostly because of the FNSAVE case, because in that
- * case we must not allow preemption in the window
- * between the FNSAVE and us marking the context lazy.
- *
- * It shouldn't be an issue as even FNSAVE is plenty
- * fast in terms of critical section length.
+ * ( The function 'fails' in the FNSAVE case, which destroys
+ * register contents so we have to copy them back. )
*/
- preempt_disable();
if (!copy_fpregs_to_fpstate(dst_fpu)) {
- memcpy(&src_fpu->state, &dst_fpu->state,
- fpu_kernel_xstate_size);
-
+ memcpy(&src_fpu->state, &dst_fpu->state, fpu_kernel_xstate_size);
copy_kernel_to_fpregs(&src_fpu->state);
}
- preempt_enable();
trace_x86_fpu_copy_src(src_fpu);
trace_x86_fpu_copy_dst(dst_fpu);
--
2.11.0
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[PATCH 00/33] x86 FPU fixes and cleanups for v4.14 Ingo Molnar <mingo@kernel.org> - 2017-09-23 15:10 +0200
[PATCH 19/33] x86/fpu: Decouple fpregs_activate()/fpregs_deactivate() from fpu->fpregs_active Ingo Molnar <mingo@kernel.org> - 2017-09-23 15:10 +0200
[tip:x86/fpu] x86/fpu: Decouple fpregs_activate()/fpregs_deactivate() from fpu->fpregs_active tip-bot for Ingo Molnar <tipbot@zytor.com> - 2017-09-26 10:40 +0200
[PATCH 15/33] x86/fpu: Simplify fpu->fpregs_active use Ingo Molnar <mingo@kernel.org> - 2017-09-23 15:10 +0200
[tip:x86/fpu] x86/fpu: Simplify fpu->fpregs_active use tip-bot for Ingo Molnar <tipbot@zytor.com> - 2017-09-26 10:40 +0200
[PATCH 26/33] x86/fpu: Reinitialize FPU registers if restoring FPU state fails Ingo Molnar <mingo@kernel.org> - 2017-09-23 15:10 +0200
[tip:x86/fpu] x86/fpu: Reinitialize FPU registers if restoring FPU state fails tip-bot for Eric Biggers <tipbot@zytor.com> - 2017-09-26 10:40 +0200
[PATCH 32/33] x86/fpu: Rename fpu__activate_curr() to fpu__initialize() Ingo Molnar <mingo@kernel.org> - 2017-09-23 15:10 +0200
[tip:x86/fpu] x86/fpu: Rename fpu__activate_curr() to fpu__initialize() tip-bot for Ingo Molnar <tipbot@zytor.com> - 2017-09-26 10:50 +0200
[PATCH 31/33] x86/fpu: Simplify and speed up fpu__copy() Ingo Molnar <mingo@kernel.org> - 2017-09-23 15:10 +0200
[tip:x86/fpu] x86/fpu: Simplify and speed up fpu__copy() tip-bot for Ingo Molnar <tipbot@zytor.com> - 2017-09-26 10:50 +0200
[PATCH 21/33] x86/fpu: Add FPU state copying quirk to handle XRSTOR failure on Intel Skylake CPUs Ingo Molnar <mingo@kernel.org> - 2017-09-23 15:10 +0200
[tip:x86/fpu] x86/fpu: Add FPU state copying quirk to handle XRSTOR failure on Intel Skylake CPUs tip-bot for Rik van Riel <tipbot@zytor.com> - 2017-09-26 10:40 +0200
[PATCH 13/33] x86/fpu: Remove 'kbuf' parameter from the copy_user_to_xstate() API Ingo Molnar <mingo@kernel.org> - 2017-09-23 15:10 +0200
[tip:x86/fpu] x86/fpu: Remove 'kbuf' parameter from the copy_user_to_xstate() API tip-bot for Ingo Molnar <tipbot@zytor.com> - 2017-09-26 10:40 +0200
[PATCH 33/33] x86/fpu: Rename fpu__activate_fpstate_read/write() to fpu__read/write() Ingo Molnar <mingo@kernel.org> - 2017-09-23 15:10 +0200
[PATCH 02/33] x86/fpu: Split copy_xstate_to_user() into copy_xstate_to_kernel() & copy_xstate_to_user() Ingo Molnar <mingo@kernel.org> - 2017-09-23 15:10 +0200
[tip:x86/fpu] x86/fpu: Split copy_xstate_to_user() into copy_xstate_to_kernel() & copy_xstate_to_user() tip-bot for Ingo Molnar <tipbot@zytor.com> - 2017-09-26 10:30 +0200
[PATCH 16/33] x86/fpu: Make the fpu state change in fpu__clear() scheduler-atomic Ingo Molnar <mingo@kernel.org> - 2017-09-23 15:10 +0200
[tip:x86/fpu] x86/fpu: Make the fpu state change in fpu__clear() scheduler-atomic tip-bot for Ingo Molnar <tipbot@zytor.com> - 2017-09-26 10:40 +0200
[PATCH 14/33] x86/fpu: Flip the parameter order in copy_*_to_xstate() Ingo Molnar <mingo@kernel.org> - 2017-09-23 15:10 +0200
[tip:x86/fpu] x86/fpu: Flip the parameter order in copy_*_to_xstate() tip-bot for Ingo Molnar <tipbot@zytor.com> - 2017-09-26 10:40 +0200
[PATCH 11/33] x86/fpu: Split copy_user_to_xstate() into copy_kernel_to_xstate() & copy_user_to_xstate() Ingo Molnar <mingo@kernel.org> - 2017-09-23 15:10 +0200
[tip:x86/fpu] x86/fpu: Split copy_user_to_xstate() into copy_kernel_to_xstate() & copy_user_to_xstate() tip-bot for Ingo Molnar <tipbot@zytor.com> - 2017-09-26 10:40 +0200
[PATCH 07/33] x86/fpu: Remove the 'start_pos' parameter from the __copy_xstate_to_*() functions Ingo Molnar <mingo@kernel.org> - 2017-09-23 15:10 +0200
[tip:x86/fpu] x86/fpu: Remove the 'start_pos' parameter from the __copy_xstate_to_*() functions tip-bot for Ingo Molnar <tipbot@zytor.com> - 2017-09-26 10:40 +0200
[PATCH 01/33] x86/fpu: Rename copyin_to_xsaves()/copyout_from_xsaves() to copy_user_to_xstate()/copy_xstate_to_user() Ingo Molnar <mingo@kernel.org> - 2017-09-23 15:10 +0200
[tip:x86/fpu] x86/fpu: Rename copyin_to_xsaves()/copyout_from_xsaves() to copy_user_to_xstate()/copy_xstate_to_user() tip-bot for Ingo Molnar <tipbot@zytor.com> - 2017-09-26 10:30 +0200
[PATCH 29/33] x86/fpu: Rename fpu::fpstate_active to fpu::initialized Ingo Molnar <mingo@kernel.org> - 2017-09-23 15:10 +0200
[tip:x86/fpu] x86/fpu: Rename fpu::fpstate_active to fpu::initialized tip-bot for Ingo Molnar <tipbot@zytor.com> - 2017-09-26 10:50 +0200
[PATCH 17/33] x86/fpu: Split the state handling in fpu__drop() Ingo Molnar <mingo@kernel.org> - 2017-09-23 15:10 +0200
[tip:x86/fpu] x86/fpu: Split the state handling in fpu__drop() tip-bot for Ingo Molnar <tipbot@zytor.com> - 2017-09-26 10:40 +0200
[PATCH 09/33] x86/fpu: Change 'size_total' parameter to unsigned and standardize the size checks in copy_xstate_to_*() Ingo Molnar <mingo@kernel.org> - 2017-09-23 15:10 +0200
[tip:x86/fpu] x86/fpu: Change 'size_total' parameter to unsigned and standardize the size checks in copy_xstate_to_*() tip-bot for Ingo Molnar <tipbot@zytor.com> - 2017-09-26 10:40 +0200
[PATCH 30/33] x86/fpu: Fix stale comments about lazy FPU logic Ingo Molnar <mingo@kernel.org> - 2017-09-23 15:10 +0200
[tip:x86/fpu] x86/fpu: Fix stale comments about lazy FPU logic tip-bot for Ingo Molnar <tipbot@zytor.com> - 2017-09-26 10:50 +0200
[PATCH 08/33] x86/fpu: Clarify parameter names in the copy_xstate_to_*() methods Ingo Molnar <mingo@kernel.org> - 2017-09-23 15:10 +0200
Re: [PATCH 08/33] x86/fpu: Clarify parameter names in the copy_xstate_to_*() methods Thomas Gleixner <tglx@linutronix.de> - 2017-09-25 22:00 +0200
Re: [PATCH 08/33] x86/fpu: Clarify parameter names in the copy_xstate_to_*() methods Thomas Gleixner <tglx@linutronix.de> - 2017-09-25 22:10 +0200
[tip:x86/fpu] x86/fpu: Clarify parameter names in the copy_xstate_to_*() methods tip-bot for Ingo Molnar <tipbot@zytor.com> - 2017-09-26 10:40 +0200
[PATCH 20/33] x86/fpu: Remove struct fpu::fpregs_active Ingo Molnar <mingo@kernel.org> - 2017-09-23 15:10 +0200
[tip:x86/fpu] x86/fpu: Remove struct fpu::fpregs_active tip-bot for Ingo Molnar <tipbot@zytor.com> - 2017-09-26 10:40 +0200
[PATCH 03/33] x86/fpu: Remove 'ubuf' parameter from the copy_xstate_to_kernel() APIs Ingo Molnar <mingo@kernel.org> - 2017-09-23 15:10 +0200
[tip:x86/fpu] x86/fpu: Remove 'ubuf' parameter from the copy_xstate_to_kernel() APIs tip-bot for Ingo Molnar <tipbot@zytor.com> - 2017-09-26 10:30 +0200
[PATCH 23/33] x86/fpu: Turn WARN_ON() in context switch into WARN_ON_FPU() Ingo Molnar <mingo@kernel.org> - 2017-09-23 15:10 +0200
[tip:x86/fpu] x86/fpu: Turn WARN_ON() in context switch into WARN_ON_FPU() tip-bot for Andi Kleen <tipbot@zytor.com> - 2017-09-26 10:40 +0200
[PATCH 22/33] x86/fpu: Fix boolreturn.cocci warnings Ingo Molnar <mingo@kernel.org> - 2017-09-23 15:10 +0200
[tip:x86/fpu] x86/fpu: Fix boolreturn.cocci warnings tip-bot for kbuild test robot <tipbot@zytor.com> - 2017-09-26 10:40 +0200
[PATCH 06/33] x86/fpu: Clean up the parameter definitions of copy_xstate_to_*() Ingo Molnar <mingo@kernel.org> - 2017-09-23 15:10 +0200
[tip:x86/fpu] x86/fpu: Clean up the parameter definitions of copy_xstate_to_*() tip-bot for Ingo Molnar <tipbot@zytor.com> - 2017-09-26 10:40 +0200
[PATCH 04/33] x86/fpu: Remove 'kbuf' parameter from the copy_xstate_to_user() APIs Ingo Molnar <mingo@kernel.org> - 2017-09-23 15:10 +0200
[tip:x86/fpu] x86/fpu: Remove 'kbuf' parameter from the copy_xstate_to_user() APIs tip-bot for Ingo Molnar <tipbot@zytor.com> - 2017-09-26 10:40 +0200
[PATCH 05/33] x86/fpu: Clean up parameter order in the copy_xstate_to_*() APIs Ingo Molnar <mingo@kernel.org> - 2017-09-23 15:10 +0200
[tip:x86/fpu] x86/fpu: Clean up parameter order in the copy_xstate_to_*() APIs tip-bot for Ingo Molnar <tipbot@zytor.com> - 2017-09-26 10:40 +0200
[PATCH 24/33] x86/fpu: Don't let userspace set bogus xcomp_bv Ingo Molnar <mingo@kernel.org> - 2017-09-23 15:10 +0200
[tip:x86/fpu] x86/fpu: Don't let userspace set bogus xcomp_bv tip-bot for Eric Biggers <tipbot@zytor.com> - 2017-09-26 10:50 +0200
[PATCH 18/33] x86/fpu: Change fpu->fpregs_active users to fpu->fpstate_active Ingo Molnar <mingo@kernel.org> - 2017-09-23 15:10 +0200
[tip:x86/fpu] x86/fpu: Change fpu->fpregs_active users to fpu->fpstate_active tip-bot for Ingo Molnar <tipbot@zytor.com> - 2017-09-26 10:40 +0200
[PATCH 27/33] x86/fpu: Simplify fpu__activate_fpstate_read() Ingo Molnar <mingo@kernel.org> - 2017-09-23 15:10 +0200
[tip:x86/fpu] x86/fpu: Fix fpu__activate_fpstate_read() and update comments tip-bot for Ingo Molnar <tipbot@zytor.com> - 2017-09-26 10:40 +0200
[PATCH 12/33] x86/fpu: Remove 'ubuf' parameter from the copy_kernel_to_xstate() API Ingo Molnar <mingo@kernel.org> - 2017-09-23 15:10 +0200
[tip:x86/fpu] x86/fpu: Remove 'ubuf' parameter from the copy_kernel_to_xstate() API tip-bot for Ingo Molnar <tipbot@zytor.com> - 2017-09-26 10:40 +0200
[PATCH 25/33] x86/fpu: Tighten validation of user-supplied xstate_header Ingo Molnar <mingo@kernel.org> - 2017-09-23 15:10 +0200
[PATCH 28/33] x86/fpu: Remove fpu__current_fpstate_write_begin/end() Ingo Molnar <mingo@kernel.org> - 2017-09-23 15:10 +0200
[tip:x86/fpu] x86/fpu: Remove fpu__current_fpstate_write_begin/end() tip-bot for Ingo Molnar <tipbot@zytor.com> - 2017-09-26 10:40 +0200
Re: [PATCH 00/33] x86 FPU fixes and cleanups for v4.14 Ingo Molnar <mingo@kernel.org> - 2017-09-23 15:10 +0200
Re: [PATCH 00/33] x86 FPU fixes and cleanups for v4.14 Juergen Gross <jgross@suse.com> - 2017-09-23 17:10 +0200
Re: [PATCH 00/33] x86 FPU fixes and cleanups for v4.14 Ingo Molnar <mingo@kernel.org> - 2017-09-24 01:30 +0200
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