linux-kernel - Re: [PATCH v5 2/2] KVM: X86: Allow userspace to define the microcode version

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Date:   Wed, 28 Feb 2018 13:59:24 +0800
From:   Wanpeng Li <kernellwp@...il.com>
To:     Tom Lendacky <thomas.lendacky@....com>
Cc:     LKML <linux-kernel@...r.kernel.org>, kvm <kvm@...r.kernel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Liran Alon <liran.alon@...cle.com>,
        Nadav Amit <nadav.amit@...il.com>,
        Borislav Petkov <bp@...en8.de>
Subject: Re: [PATCH v5 2/2] KVM: X86: Allow userspace to define the microcode version

2018-02-28 13:55 GMT+08:00 Tom Lendacky <thomas.lendacky@....com>:
> On 2/27/2018 9:34 PM, Wanpeng Li wrote:
>> From: Wanpeng Li <wanpengli@...cent.com>
>>
>> Linux (among the others) has checks to make sure that certain features
>> aren't enabled on a certain family/model/stepping if the microcode version
>> isn't greater than or equal to a known good version.
>>
>> By exposing the real microcode version, we're preventing buggy guests that
>> don't check that they are running virtualized (i.e., they should trust the
>> hypervisor) from disabling features that are effectively not buggy.
>>
>> Suggested-by: Filippo Sironi <sironi@...zon.de>
>> Cc: Paolo Bonzini <pbonzini@...hat.com>
>> Cc: Radim Krčmář <rkrcmar@...hat.com>
>> Cc: Liran Alon <liran.alon@...cle.com>
>> Cc: Nadav Amit <nadav.amit@...il.com>
>> Cc: Borislav Petkov <bp@...en8.de>
>> Cc: Tom Lendacky <thomas.lendacky@....com>
>> Signed-off-by: Wanpeng Li <wanpengli@...cent.com>
>> ---
>> v4 -> v5:
>>  * microcode_version be u64 and initialized suitable, remote hte shifts
>> v3 -> v4:
>>  * add the shifts back
>> v2 -> v3:
>>  * remove the shifts
>>  * add the MSR_IA32_UCODE_REV version to the "feature MSRs"
>
> I think you lost this part from the patch series.  I don't see where you
> add MSR_IA32_UCODE_REV to the msr_based_features array.

I sent out a wrong version, will send again.

Regards,
Wanpeng Li