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

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Message-ID: <CANRm+CzwY2yzKFXF7r=vfqDaHHoHxC221TSBtSHC2XtvkrQxHA@mail.gmail.com>
Date:   Mon, 26 Feb 2018 19:37:32 +0800
From:   Wanpeng Li <kernellwp@...il.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     LKML <linux-kernel@...r.kernel.org>, kvm <kvm@...r.kernel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>
Subject: Re: [PATCH] KVM: X86: Allow userspace to define the microcode version

2018-02-26 19:30 GMT+08:00 Borislav Petkov <bp@...en8.de>:
> On Mon, Feb 26, 2018 at 07:25:28PM +0800, Wanpeng Li wrote:
>> Both are the same values set by kvm userspace.
>
> This still doesn't answer my question what "the non-sensical value which
> is written by the guest will not reflect to guest-visible microcode
> revision" means?

The guest write is ignored as the original kvm implementation before the patch.

>
>> This is correct. The link explains why the userspace sets microcode
>> revision is still needed.
>
> Why is it still needed?

Hmm, the apic_check_deadline_errata() example can be referred to.

Regards,
Wanpeng Li