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Re: [PATCH 3/2] x86/microcode/intel: Add a helper which gives the microcode revision

From Boris Ostrovsky <boris.ostrovsky@oracle.com>
Newsgroups linux.kernel
Subject Re: [PATCH 3/2] x86/microcode/intel: Add a helper which gives the microcode revision
Date 2016-12-28 20:30 +0100
Message-ID <sTs5b-4f0-3@gated-at.bofh.it> (permalink)
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On 12/28/2016 07:53 AM, Borislav Petkov wrote:
> On Wed, Dec 28, 2016 at 12:21:20PM +0100, Borislav Petkov wrote:
>> From: Borislav Petkov <bp@suse.de>
>>
>> Intel supplies the microcode revision value in MSR 0x8b
>> (IA32_BIOS_SIGN_ID) after CPUID(1) has been executed. Execute it each
>> time before reading that MSR.
>
> And then, we can go a step further and even do a separate helper which does the
> required steps to read out the microcode revision so that we don't forget them
> next time we change the code.
>
> Provided that works for xen, though, because I need to do the native
> variants but early_init_intel() can call the paravirt *msr() versions
> and I have no idea whether that's kosher on xen pv.
>
> Boris, any objections?

I think this should work. MSR_IA32_UCODE_REV can be natively read and 
written with zero without any side effects.

-boris

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[PATCH] x86: Fix Intel microcode revision detection Junichi Nomura <j-nomura@ce.jp.nec.com> - 2016-12-28 05:50 +0100
  [PATCH 1/2] x86/CPU: Add native CPUID variants returning a single  datum Borislav Petkov <bp@alien8.de> - 2016-12-28 12:30 +0100
    Re: [PATCH 1/2] x86/CPU: Add native CPUID variants returning a single datum Andy Lutomirski <luto@amacapital.net> - 2016-12-28 19:20 +0100
      Re: [PATCH 1/2] x86/CPU: Add native CPUID variants returning a  single datum Borislav Petkov <bp@alien8.de> - 2016-12-29 10:40 +0100
        Re: [PATCH 1/2] x86/CPU: Add native CPUID variants returning a single datum Andy Lutomirski <luto@amacapital.net> - 2016-12-31 03:20 +0100
          Re: [PATCH 1/2] x86/CPU: Add native CPUID variants returning a  single datum Borislav Petkov <bp@alien8.de> - 2016-12-31 12:20 +0100
  [PATCH 2/2] x86/microcode: Use native CPUID to tickle out microcode  revision Borislav Petkov <bp@alien8.de> - 2016-12-28 12:30 +0100
    [PATCH 3/2] x86/microcode/intel: Add a helper which gives the  microcode revision Borislav Petkov <bp@alien8.de> - 2016-12-28 14:00 +0100
      Re: [PATCH 3/2] x86/microcode/intel: Add a helper which gives the  microcode revision Andy Lutomirski <luto@amacapital.net> - 2016-12-28 19:20 +0100
        Re: [PATCH 3/2] x86/microcode/intel: Add a helper which gives the  microcode revision Borislav Petkov <bp@alien8.de> - 2016-12-29 10:40 +0100
      Re: [PATCH 3/2] x86/microcode/intel: Add a helper which gives the  microcode revision Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2016-12-28 20:30 +0100
        Re: [PATCH 3/2] x86/microcode/intel: Add a helper which gives the  microcode revision Borislav Petkov <bp@alien8.de> - 2016-12-29 10:40 +0100
  Re: [PATCH] x86: Fix Intel microcode revision detection Borislav Petkov <bp@alien8.de> - 2016-12-28 12:30 +0100

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