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Re: [PATCH 1/5] x86/entry/32: Clean up enable_sep_cpu to prepare for 64-bit merge

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On Thu, Jul 23, 2015 at 12:02 PM, Andy Lutomirski <luto@amacapital.net> wrote:
> On Thu, Jul 23, 2015 at 8:56 AM, Steven Rostedt <rostedt@goodmis.org> wrote:
>> On Thu, 23 Jul 2015 08:31:39 -0700
>> Andy Lutomirski <luto@kernel.org> wrote:
>>
>>> Switch from wrmsr to wrmsrl_safe to prepare to merge the 32-bit and
>>> 64-bit code, and use __KERNEL_CS explicitly to initialize
>>> MSR_IA32_SYSENTER_CS.  While we're at it, tweak the whitespace a
>>> bit.
>>
>> Saying "prepare to merge the 32-bit and 64-bit" isn't that informative
>> to why this patch is needed. Can you please describe in the change log
>> what can fault with the wrmsr call, when we do the merge?
>
> Oh...
>
> Nothing can fault in the wrmsr as far as I know, but maybe there's a
> CPU out there that advertises SEP but doesn't have the MSRs.
>
> Ingo, Thomas, want a v2 that explains that the wrmsr_safe is there for
> consistency but that I don't know why 32bit does it?  Another option
> would be to remove the _safe from the 32-bit version.

There is an erratum with SEP being advertised but not available on
early P6 models, but we already check for that in the cpu setup code.
There shouldn't be a problem with a fault.

--
Brian Gerst
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Re: [PATCH 1/5] x86/entry/32: Clean up enable_sep_cpu to prepare for  64-bit merge Brian Gerst <brgerst@gmail.com> - 2015-07-23 19:30 +0200
  Re: [PATCH 1/5] x86/entry/32: Clean up enable_sep_cpu to prepare for  64-bit merge Andy Lutomirski <luto@amacapital.net> - 2015-07-23 20:10 +0200
    Re: [PATCH 1/5] x86/entry/32: Clean up enable_sep_cpu to prepare for  64-bit merge Andy Lutomirski <luto@amacapital.net> - 2015-07-23 20:40 +0200
      Re: [PATCH 1/5] x86/entry/32: Clean up enable_sep_cpu to prepare for  64-bit merge Andy Lutomirski <luto@amacapital.net> - 2015-07-23 20:50 +0200
        Re: [PATCH 1/5] x86/entry/32: Clean up enable_sep_cpu to prepare for  64-bit merge Linus Torvalds <torvalds@linux-foundation.org> - 2015-07-23 21:00 +0200

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