Re: [PATCH v5 12/13] x86/xsaves: Fix fpstate_init() for XSAVES

From	Dave Hansen <dave.hansen@linux.intel.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH v5 12/13] x86/xsaves: Fix fpstate_init() for XSAVES
Date	2016-05-10 02:10 +0200
Message-ID	<rx3pp-81T-41@gated-at.bofh.it> (permalink)
References	<rx0rx-4yi-11@gated-at.bofh.it> <rx0ry-4yi-45@gated-at.bofh.it> <rx362-7sX-29@gated-at.bofh.it> <rx3fI-7Ae-7@gated-at.bofh.it>
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On 05/09/2016 04:50 PM, Yu-cheng Yu wrote:
>> > 
>> > Oh, and if you decided to do this for some reason, please have mercy and
>> > go make a macro for 1<<63.
>> > 
>> > Also, I don't think the kernel ever checks for this bit.  So are we
>> > really calling XRSTORS on otherwise uninitialized xsave buffers?
> Right now if we do fpstate_init(), without this patch, it will 
> trigger a warning from copy_kernel_to_fxregs() when the task is
> scheduled.

Please include this in the patch description.  It's a pretty important
piece of justification.  Did you mean "copy_kernel_to_xregs()" without
the "f"?

I think we should probably also have an _explicit_ FPU_WARN_ON() in the
XRSTORS path for this.  *Both* the booting and regular ones, btw...

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[PATCH v5 12/13] x86/xsaves: Fix fpstate_init() for XSAVES Yu-cheng Yu <yu-cheng.yu@intel.com> - 2016-05-09 23:00 +0200
  Re: [PATCH v5 12/13] x86/xsaves: Fix fpstate_init() for XSAVES Dave Hansen <dave.hansen@linux.intel.com> - 2016-05-10 01:50 +0200
    Re: [PATCH v5 12/13] x86/xsaves: Fix fpstate_init() for XSAVES Yu-cheng Yu <yu-cheng.yu@intel.com> - 2016-05-10 02:00 +0200
      Re: [PATCH v5 12/13] x86/xsaves: Fix fpstate_init() for XSAVES Dave Hansen <dave.hansen@linux.intel.com> - 2016-05-10 02:10 +0200

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