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Groups > linux.kernel > #1354091 > unrolled thread
| Started by | Ingo Molnar <mingo@kernel.org> |
|---|---|
| First post | 2016-03-09 13:50 +0100 |
| Last post | 2016-03-09 20:00 +0100 |
| Articles | 4 — 3 participants |
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Re: [PATCH] x86/fpu: Revert earlier patch of Disable AVX when eagerfpu is off Ingo Molnar <mingo@kernel.org> - 2016-03-09 13:50 +0100
Re: [PATCH] x86/fpu: Revert earlier patch of Disable AVX when eagerfpu is off Yu-cheng Yu <yu-cheng.yu@intel.com> - 2016-03-09 18:30 +0100
Re: [PATCH] x86/fpu: Revert earlier patch of Disable AVX when eagerfpu is off Ingo Molnar <mingo@kernel.org> - 2016-03-09 19:50 +0100
Re: [PATCH] x86/fpu: Revert earlier patch of Disable AVX when eagerfpu is off "H. Peter Anvin" <hpa@zytor.com> - 2016-03-09 20:00 +0100
| From | Ingo Molnar <mingo@kernel.org> |
|---|---|
| Date | 2016-03-09 13:50 +0100 |
| Subject | Re: [PATCH] x86/fpu: Revert earlier patch of Disable AVX when eagerfpu is off |
| Message-ID | <raLIS-7XZ-15@gated-at.bofh.it> |
* Yu-cheng Yu <yu-cheng.yu@intel.com> 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
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| From | Yu-cheng Yu <yu-cheng.yu@intel.com> |
|---|---|
| Date | 2016-03-09 18:30 +0100 |
| Message-ID | <raQ5Q-2LL-17@gated-at.bofh.it> |
| In reply to | #1354091 |
On Wed, Mar 09, 2016 at 01:46:26PM +0100, Ingo Molnar wrote: > > * Yu-cheng Yu <yu-cheng.yu@intel.com> 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
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| From | Ingo Molnar <mingo@kernel.org> |
|---|---|
| Date | 2016-03-09 19:50 +0100 |
| Message-ID | <raRlg-3wv-13@gated-at.bofh.it> |
| In reply to | #1354301 |
* Yu-cheng Yu <yu-cheng.yu@intel.com> wrote: > On Wed, Mar 09, 2016 at 01:46:26PM +0100, Ingo Molnar wrote: > > > > * Yu-cheng Yu <yu-cheng.yu@intel.com> 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
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| From | "H. Peter Anvin" <hpa@zytor.com> |
|---|---|
| Date | 2016-03-09 20:00 +0100 |
| Message-ID | <raRuW-3zK-15@gated-at.bofh.it> |
| In reply to | #1354091 |
On 03/09/2016 04:46 AM, Ingo Molnar wrote: > > * Yu-cheng Yu <yu-cheng.yu@intel.com> 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
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