linux-kernel - Re: [PATCH v3] KVM: X86: Allow userspace to define the microcode version

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Date:   Tue, 27 Feb 2018 09:36:48 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Wanpeng Li <kernellwp@...il.com>, Nadav Amit <nadav.amit@...il.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, kvm <kvm@...r.kernel.org>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Liran Alon <liran.alon@...cle.com>
Subject: Re: [PATCH v3] KVM: X86: Allow userspace to define the microcode
 version

On 27/02/2018 03:22, Wanpeng Li wrote:
>>> @@ -2551,7 +2561,7 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>>>               msr_info->data = 0;
>>>               break;
>>>       case MSR_IA32_UCODE_REV:
>>> -             msr_info->data = 0x100000000ULL;
>>> +             msr_info->data = (u64)vcpu->arch.microcode_version;
>> I think that the shifts are missing here (the version should be on the high
>> bits according to intel_get_microcode_revision() ).
> You are right, it seems that we all miss it before.

It's not that the shift are missing.  It's that microcode_version should
be u64 and initialized to 0x100000000ULL.  Sorry I was too concise in my
review of v2, and made that implicit.

(Boris noticed offlist that AMD places the revision is in bit 0-31).

Thanks,

Paolo