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Groups > linux.kernel > #1517395
| From | Peter Zijlstra <peterz@infradead.org> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH 2/4] x86: Prepare vm86 tasks to handle User-Mode Instruction Prevention |
| Date | 2016-11-08 18:10 +0100 |
| Message-ID | <sBi4i-3IU-31@gated-at.bofh.it> (permalink) |
| References | <sB7Vg-5Hp-5@gated-at.bofh.it> <sB7Vg-5Hp-27@gated-at.bofh.it> <sBh8e-37L-13@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On Tue, Nov 08, 2016 at 08:01:39AM -0800, Andy Lutomirski wrote:
> > diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
> > index 0888a87..32b7301 100644
> > --- a/arch/x86/kernel/process.c
> > +++ b/arch/x86/kernel/process.c
> > @@ -233,6 +233,16 @@ void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p,
> > */
> > memset(tss->io_bitmap, 0xff, prev->io_bitmap_max);
> > }
> > +
> > +#if defined(CONFIG_VM86) && defined(CONFIG_X86_INTEL_UMIP)
> > + if (next->vm86 && next->vm86->saved_sp0 && next->vm86->disable_x86_umip)
> > + cr4_clear_bits(X86_CR4_UMIP);
> > + else {
> > + if (static_cpu_has(X86_FEATURE_UMIP))
> > + cr4_set_bits(X86_CR4_UMIP);
> > + }
> > +#endif
> > +
>
> NAK. If this code is going to exist, it needs to be deeply buried in
> some unlikely if statement that already exists. There's no good
> reason to penalize all context switches to support some nonsensical
> vm86 use case.
Agreed, now if instead vm86 get to emulate these instructions, this all
magically goes away..
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[PATCH 0/4] x86: enable User-Mode Instruction Prevention Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2016-11-08 07:20 +0100
[PATCH 3/4] x86: Enable User-Mode Instruction Prevention Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2016-11-08 07:20 +0100
[PATCH 4/4] selftests/x86: Add tests for User-Mode Instruction Prevention Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2016-11-08 07:20 +0100
[PATCH 2/4] x86: Prepare vm86 tasks to handle User-Mode Instruction Prevention Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2016-11-08 07:20 +0100
Re: [PATCH 2/4] x86: Prepare vm86 tasks to handle User-Mode Instruction Prevention Andy Lutomirski <luto@amacapital.net> - 2016-11-08 17:10 +0100
Re: [PATCH 2/4] x86: Prepare vm86 tasks to handle User-Mode Instruction Prevention Peter Zijlstra <peterz@infradead.org> - 2016-11-08 18:10 +0100
Re: [PATCH 2/4] x86: Prepare vm86 tasks to handle User-Mode Instruction Prevention Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2016-11-09 05:30 +0100
Re: [PATCH 0/4] x86: enable User-Mode Instruction Prevention Peter Zijlstra <peterz@infradead.org> - 2016-11-08 14:20 +0100
Re: [PATCH 0/4] x86: enable User-Mode Instruction Prevention Andy Lutomirski <luto@amacapital.net> - 2016-11-08 16:40 +0100
Re: [PATCH 0/4] x86: enable User-Mode Instruction Prevention Thomas Gleixner <tglx@linutronix.de> - 2016-11-08 18:00 +0100
Re: [PATCH 0/4] x86: enable User-Mode Instruction Prevention Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2016-11-09 05:30 +0100
Re: [PATCH 0/4] x86: enable User-Mode Instruction Prevention Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2016-11-09 05:40 +0100
Re: [PATCH 0/4] x86: enable User-Mode Instruction Prevention Andy Lutomirski <luto@amacapital.net> - 2016-11-09 12:40 +0100
Re: [PATCH 0/4] x86: enable User-Mode Instruction Prevention Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2016-11-10 07:50 +0100
Re: [PATCH 0/4] x86: enable User-Mode Instruction Prevention Stas Sergeev <stsp@list.ru> - 2016-11-10 10:00 +0100
Re: [PATCH 0/4] x86: enable User-Mode Instruction Prevention Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2016-11-11 05:20 +0100
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