Re: [PATCH] x86/fpu: Revert earlier patch of Disable AVX when eagerfpu is off
On 03/09/2016 04:46 AM, Ingo Molnar wrote: > > * Yu-cheng Yu wrote: > >> AVX was mistakenly believed to be dependent on eagerfpu switch. >> This turns out to be false. The earlier patch should be reverted. >> >> Original patch: >> http://git.kernel.org/tip/394db20ca240741a08d472173db13d6f6a6e5a28 > > So the original patch had a whole host of explanations of why that change is > correct. This revert should explain where that argumentation was wrong. > > Also note that eagerfpu=off is on the way out, on v4.6 we'll switch all CPUs > to > eagerfpu: > > 58122bf1d856 x86/fpu: Default eagerfpu=on on all CPUs > > and in the not so distant future, if everything goes fine with the eager > mode, I'd > like to drop the lazy FPU context switching code altogether - which will > simplify > a lot of code. At that point the 'eagerfpu' boot option will go away as well. > Last I heard the only use case which was seeing trouble with eagerfpu was KVM during service of I/O events. Might be worth checking into... -hpa
Re: [PATCH] x86/fpu: Revert earlier patch of Disable AVX when eagerfpu is off
* Yu-cheng Yu wrote: > On Wed, Mar 09, 2016 at 01:46:26PM +0100, Ingo Molnar wrote: > > > > * Yu-cheng Yu wrote: > > > > > AVX was mistakenly believed to be dependent on eagerfpu switch. > > > This turns out to be false. The earlier patch should be reverted. > > > > > > Original patch: > > > http://git.kernel.org/tip/394db20ca240741a08d472173db13d6f6a6e5a28 > > > > So the original patch had a whole host of explanations of why that change > > is > > correct. This revert should explain where that argumentation was wrong. > > I will send out another version that includes more details. Great, thanks! Ingo
Re: [PATCH] x86/fpu: Revert earlier patch of Disable AVX when eagerfpu is off
On Wed, Mar 09, 2016 at 01:46:26PM +0100, Ingo Molnar wrote: > > * Yu-cheng Yu wrote: > > > AVX was mistakenly believed to be dependent on eagerfpu switch. > > This turns out to be false. The earlier patch should be reverted. > > > > Original patch: > > http://git.kernel.org/tip/394db20ca240741a08d472173db13d6f6a6e5a28 > > So the original patch had a whole host of explanations of why that change is > correct. This revert should explain where that argumentation was wrong. I will send out another version that includes more details. Thanks, Yu-cheng
Re: [PATCH] x86/fpu: Revert earlier patch of Disable AVX when eagerfpu is off
* Yu-cheng Yu wrote: > AVX was mistakenly believed to be dependent on eagerfpu switch. > This turns out to be false. The earlier patch should be reverted. > > Original patch: > http://git.kernel.org/tip/394db20ca240741a08d472173db13d6f6a6e5a28 So the original patch had a whole host of explanations of why that change is correct. This revert should explain where that argumentation was wrong. Also note that eagerfpu=off is on the way out, on v4.6 we'll switch all CPUs to eagerfpu: 58122bf1d856 x86/fpu: Default eagerfpu=on on all CPUs and in the not so distant future, if everything goes fine with the eager mode, I'd like to drop the lazy FPU context switching code altogether - which will simplify a lot of code. At that point the 'eagerfpu' boot option will go away as well. Thanks, Ingo
[PATCH] x86/fpu: Revert earlier patch of Disable AVX when eagerfpu is off
AVX was mistakenly believed to be dependent on eagerfpu switch.
This turns out to be false. The earlier patch should be reverted.
Original patch:
http://git.kernel.org/tip/394db20ca240741a08d472173db13d6f6a6e5a28
Signed-off-by: Yu-cheng Yu
Reported_by: Leonid Shatz
Cc: x...@kernel.org
Cc: H. Peter Anvin
Cc: Thomas Gleixner
Cc: Dave Hansen
Cc: Ingo Molnar
Cc: Borislav Petkov
Cc: Sai Praneeth Prakhya
Cc: Ravi V. Shankar
Cc: Leonid Shatz
Cc: Fenghua Yu
---
arch/x86/include/asm/fpu/xstate.h | 9 -
arch/x86/kernel/fpu/init.c| 6 --
2 files changed, 4 insertions(+), 11 deletions(-)
diff --git a/arch/x86/include/asm/fpu/xstate.h
b/arch/x86/include/asm/fpu/xstate.h
index af30fde..f23cd8c 100644
--- a/arch/x86/include/asm/fpu/xstate.h
+++ b/arch/x86/include/asm/fpu/xstate.h
@@ -20,16 +20,15 @@
/* Supported features which support lazy state saving */
#define XFEATURE_MASK_LAZY (XFEATURE_MASK_FP | \
-XFEATURE_MASK_SSE)
-
-/* Supported features which require eager state saving */
-#define XFEATURE_MASK_EAGER(XFEATURE_MASK_BNDREGS | \
-XFEATURE_MASK_BNDCSR | \
+XFEATURE_MASK_SSE | \
XFEATURE_MASK_YMM | \
XFEATURE_MASK_OPMASK | \
XFEATURE_MASK_ZMM_Hi256 | \
XFEATURE_MASK_Hi16_ZMM)
+/* Supported features which require eager state saving */
+#define XFEATURE_MASK_EAGER(XFEATURE_MASK_BNDREGS | XFEATURE_MASK_BNDCSR)
+
/* All currently supported features */
#define XCNTXT_MASK(XFEATURE_MASK_LAZY | XFEATURE_MASK_EAGER)
diff --git a/arch/x86/kernel/fpu/init.c b/arch/x86/kernel/fpu/init.c
index 6d9f0a7..f0ab368 100644
--- a/arch/x86/kernel/fpu/init.c
+++ b/arch/x86/kernel/fpu/init.c
@@ -300,12 +300,6 @@ u64 __init fpu__get_supported_xfeatures_mask(void)
static void __init fpu__clear_eager_fpu_features(void)
{
setup_clear_cpu_cap(X86_FEATURE_MPX);
- setup_clear_cpu_cap(X86_FEATURE_AVX);
- setup_clear_cpu_cap(X86_FEATURE_AVX2);
- setup_clear_cpu_cap(X86_FEATURE_AVX512F);
- setup_clear_cpu_cap(X86_FEATURE_AVX512PF);
- setup_clear_cpu_cap(X86_FEATURE_AVX512ER);
- setup_clear_cpu_cap(X86_FEATURE_AVX512CD);
}
/*
--
1.9.1
