Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1565311

Re: [tip:x86/urgent] x86/fpu: Set the xcomp_bv when we fake up a XSAVES area

Show all headers | View raw

On 01/23/2017 12:57 PM, Yu-cheng Yu wrote:
> On Mon, Jan 23, 2017 at 09:23:06AM -0800, Dave Hansen wrote:
>> On 01/23/2017 08:55 AM, Yu-cheng Yu wrote:
>>>> The best fix here would be not to paper over the issue in the copy
>>>> function but find where it got clobbered, or where some initialization
>>>> code failed to set it.
>>>
>>> Someone else reported different issues from the same bug and a different
>>> patch was just tested OK this morning.  I think that adding xfeatures bits
>>> to xcomp_bv should have been done in fpstate_init().
>>
>> Right.  So where did it get cleared out?
> 
> It is not set until a task triggers XSAVES.  We did not set it in fpstate_init()
> because there is no valid data at the time.

The code is:

> void fpstate_init(union fpregs_state *state)
> {
>         if (!static_cpu_has(X86_FEATURE_FPU)) {
>                 fpstate_init_soft(&state->soft);
>                 return;
>         }
> 
>         memset(state, 0, fpu_kernel_xstate_size);
> 
>         /*
>          * XRSTORS requires that this bit is set in xcomp_bv, or
>          * it will #GP. Make sure it is replaced after the memset().
>          */
>         if (static_cpu_has(X86_FEATURE_XSAVES))
>                 state->xsave.header.xcomp_bv = XCOMP_BV_COMPACTED_FORMAT;

That seems to set it unconditionally.  What am I missing?

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

[PATCH] x86/fpu: set the xcomp_bv when we fake up a XSAVES area Kevin Hao <haokexin@gmail.com> - 2017-01-22 10:00 +0100
  [tip:x86/urgent] x86/fpu: Set the xcomp_bv when we fake up a XSAVES  area tip-bot for Kevin Hao <tipbot@zytor.com> - 2017-01-23 09:30 +0100
    Re: [tip:x86/urgent] x86/fpu: Set the xcomp_bv when we fake up a  XSAVES area Dave Hansen <dave.hansen@linux.intel.com> - 2017-01-23 16:40 +0100
      Re: [tip:x86/urgent] x86/fpu: Set the xcomp_bv when we fake up a  XSAVES area Yu-cheng Yu <yu-cheng.yu@intel.com> - 2017-01-23 18:00 +0100
        Re: [tip:x86/urgent] x86/fpu: Set the xcomp_bv when we fake up a  XSAVES area Dave Hansen <dave.hansen@linux.intel.com> - 2017-01-23 18:30 +0100
          Re: [tip:x86/urgent] x86/fpu: Set the xcomp_bv when we fake up a  XSAVES area Yu-cheng Yu <yu-cheng.yu@intel.com> - 2017-01-23 22:10 +0100
            Re: [tip:x86/urgent] x86/fpu: Set the xcomp_bv when we fake up a  XSAVES area Dave Hansen <dave.hansen@linux.intel.com> - 2017-01-23 22:20 +0100
              Re: [tip:x86/urgent] x86/fpu: Set the xcomp_bv when we fake up a  XSAVES area Yu-cheng Yu <yu-cheng.yu@intel.com> - 2017-01-23 22:30 +0100
                Re: [tip:x86/urgent] x86/fpu: Set the xcomp_bv when we fake up a  XSAVES area Dave Hansen <dave.hansen@linux.intel.com> - 2017-01-23 22:30 +0100
                Re: [tip:x86/urgent] x86/fpu: Set the xcomp_bv when we fake up a  XSAVES area Kevin Hao <haokexin@gmail.com> - 2017-01-24 01:20 +0100
                Re: [tip:x86/urgent] x86/fpu: Set the xcomp_bv when we fake up a  XSAVES area Dave Hansen <dave.hansen@linux.intel.com> - 2017-01-24 02:00 +0100
                Re: [tip:x86/urgent] x86/fpu: Set the xcomp_bv when we fake up a  XSAVES area Kevin Hao <haokexin@gmail.com> - 2017-01-24 03:00 +0100
                Re: [tip:x86/urgent] x86/fpu: Set the xcomp_bv when we fake up a  XSAVES area Dave Hansen <dave.hansen@linux.intel.com> - 2017-01-24 03:10 +0100
                Re: [tip:x86/urgent] x86/fpu: Set the xcomp_bv when we fake up a  XSAVES area Kevin Hao <haokexin@gmail.com> - 2017-01-24 03:20 +0100
                Re: [tip:x86/urgent] x86/fpu: Set the xcomp_bv when we fake up a  XSAVES area Dave Hansen <dave.hansen@linux.intel.com> - 2017-01-24 03:40 +0100
                Re: [tip:x86/urgent] x86/fpu: Set the xcomp_bv when we fake up a  XSAVES area Kevin Hao <haokexin@gmail.com> - 2017-01-24 06:20 +0100
                Re: [tip:x86/urgent] x86/fpu: Set the xcomp_bv when we fake up a  XSAVES area Ingo Molnar <mingo@kernel.org> - 2017-01-24 09:10 +0100
  [tip:x86/urgent] x86/fpu: Set the xcomp_bv when we fake up a XSAVES  area tip-bot for Kevin Hao <tipbot@zytor.com> - 2017-01-23 10:50 +0100

csiph-web