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Groups > linux.kernel > #1392386
| From | Yu-cheng Yu <yu-cheng.yu@intel.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH v4 04/10] x86/xsaves: Introduce a new check that allows correct xstates copy from kernel to user directly |
| Date | 2016-05-02 19:30 +0200 |
| Message-ID | <rupPt-7D1-21@gated-at.bofh.it> (permalink) |
| References | (4 earlier) <rtr6V-76c-1@gated-at.bofh.it> <ruoA2-6AD-25@gated-at.bofh.it> <ruoA2-6AD-23@gated-at.bofh.it> <rup35-6RX-21@gated-at.bofh.it> <rupcJ-6XH-3@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On Mon, May 02, 2016 at 09:43:47AM -0700, Dave Hansen wrote:
> > If (fpu.fpstate_active == 0), then the task does not use FPU; we don't
> > want to save these registers, right?
>
> No. It's possible to have fpstate_active=0 while fpregs_active=1. Such
> a task uses the FPU, but just hasn't done an XSAVE* to save the register
> content to the fpstate buffer.
>
> Note, this is just theoretical, and does not happen in this particular
> call path today.
What about...
static int may_copy_fpregs_to_sigframe(void)
{
if (fpregs_active())
return 1;
WARN_ONCE(!current->thread.fpu.fpstate_active,
"direct FPU save with no math use\n");
if (boot_cpu_has(X86_FEATURE_XSAVES))
return 1;
return 0;
}
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Re: [PATCH v4 04/10] x86/xsaves: Introduce a new check that allows correct xstates copy from kernel to user directly Dave Hansen <dave.hansen@linux.intel.com> - 2016-04-29 22:10 +0200
Re: [PATCH v4 04/10] x86/xsaves: Introduce a new check that allows correct xstates copy from kernel to user directly Yu-cheng Yu <yu-cheng.yu@intel.com> - 2016-04-30 00:50 +0200
Re: [PATCH v4 04/10] x86/xsaves: Introduce a new check that allows correct xstates copy from kernel to user directly Dave Hansen <dave.hansen@linux.intel.com> - 2016-04-30 02:40 +0200
Re: [PATCH v4 04/10] x86/xsaves: Introduce a new check that allows correct xstates copy from kernel to user directly Dave Hansen <dave.hansen@linux.intel.com> - 2016-05-02 18:10 +0200
Re: [PATCH v4 04/10] x86/xsaves: Introduce a new check that allows correct xstates copy from kernel to user directly Yu-cheng Yu <yu-cheng.yu@intel.com> - 2016-05-02 18:40 +0200
Re: [PATCH v4 04/10] x86/xsaves: Introduce a new check that allows correct xstates copy from kernel to user directly Dave Hansen <dave.hansen@linux.intel.com> - 2016-05-02 18:50 +0200
Re: [PATCH v4 04/10] x86/xsaves: Introduce a new check that allows correct xstates copy from kernel to user directly Yu-cheng Yu <yu-cheng.yu@intel.com> - 2016-05-02 19:30 +0200
Re: [PATCH v4 04/10] x86/xsaves: Introduce a new check that allows correct xstates copy from kernel to user directly Dave Hansen <dave.hansen@linux.intel.com> - 2016-05-02 19:40 +0200
Re: [PATCH v4 04/10] x86/xsaves: Introduce a new check that allows correct xstates copy from kernel to user directly Yu-cheng Yu <yu-cheng.yu@intel.com> - 2016-05-02 23:30 +0200
Re: [PATCH v4 04/10] x86/xsaves: Introduce a new check that allows correct xstates copy from kernel to user directly Yu-cheng Yu <yu-cheng.yu@intel.com> - 2016-05-02 23:30 +0200
Re: [PATCH v4 04/10] x86/xsaves: Introduce a new check that allows correct xstates copy from kernel to user directly Dave Hansen <dave.hansen@linux.intel.com> - 2016-05-02 23:40 +0200
Re: [PATCH v4 04/10] x86/xsaves: Introduce a new check that allows correct xstates copy from kernel to user directly Yu-cheng Yu <yu-cheng.yu@intel.com> - 2016-05-03 00:30 +0200
Re: [PATCH v4 04/10] x86/xsaves: Introduce a new check that allows correct xstates copy from kernel to user directly Dave Hansen <dave.hansen@linux.intel.com> - 2016-05-03 00:40 +0200
Re: [PATCH v4 04/10] x86/xsaves: Introduce a new check that allows correct xstates copy from kernel to user directly Yu-cheng Yu <yu-cheng.yu@intel.com> - 2016-05-02 18:10 +0200
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