Re: [PATCH] KVM: X86: Allow userspace to define the microcode version

Wanpeng Li
2018-02-26T11:25:34Z

2018-02-26 19:16 GMT+08:00 Borislav Petkov <bp@alien8.de>:
> On Mon, Feb 26, 2018 at 07:02:29PM +0800, Wanpeng Li wrote:
>> > So a guest will have *two* microcode revisions - both of which are most
>> > likely wrong?!
>>
>> Just one revision.
>
> So what does "the non-sensical value which is written by the guest will
> not reflect to guest-visible microcode revision" even mean then?
>
> cat /proc/cpuinfo
>
> in the guest shows what exactly?
>
> And what would RDMSR 0x8b show then?

Both are the same values set by kvm userspace.

>
>> https://lkml.org/lkml/2017/12/9/29 The original discussion explain in
>> more details.
>

> approach. Instead, the kernel should not look at microcode revisions if
> it runs virtualized.

This is correct. The link explains why the userspace sets microcode
revision is still needed.

Regards,
Wanpeng Li