Re: [PATCH 0/3] x86/paravirt: Fix baremetal paravirt MSR ops

From: H. Peter Anvin
Date: Thu Sep 17 2015 - 07:24:23 EST


However, the difference between one CONFIG and another is quite frankly crazy. We should explicitly use the safe versions where this is appropriate, and then yes, we should do this.

Yet another reason the paravirt code is batshit crazy.

On September 17, 2015 2:31:34 AM PDT, Borislav Petkov <bp@xxxxxxxxx> wrote:
>On Thu, Sep 17, 2015 at 09:19:20AM +0200, Ingo Molnar wrote:
>> Most big distro kernels on bare metal have CONFIG_PARAVIRT=y (I
>checked Ubuntu and
>> Fedora), so we are potentially exposing a lot of users to problems.
>
>+ SUSE.
>
>> Crashing the bootup on an unknown MSR is bad. Many MSR reads and
>writes are
>> non-critical and returning the 'safe' result is much better than
>crashing or
>> hanging the bootup.
>
>... and prepending all MSR accesses with feature/CPUID checks is
>probably almost
>impossible.

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