linux-kernel - Re: [PATCH v4 24/25] KVM: VMX: Cache MSR_IA32_VMX_MISC in vmcs

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Message-ID: <87fsie1v8q.fsf@redhat.com>
Date:   Tue, 02 Aug 2022 18:11:01 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
        Anirudh Rayabharam <anrayabh@...ux.microsoft.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Maxim Levitsky <mlevitsk@...hat.com>,
        linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 24/25] KVM: VMX: Cache MSR_IA32_VMX_MISC in vmcs_config

Sean Christopherson <seanjc@...gle.com> writes:

> On Thu, Jul 14, 2022, Vitaly Kuznetsov wrote:
>> @@ -2613,6 +2614,8 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf,
>>  	if (((vmx_msr_high >> 18) & 15) != 6)
>>  		return -EIO;
>>  
>> +	rdmsrl(MSR_IA32_VMX_MISC, misc_msr);
>
> Might make sense to sanitize fields that KVM doesn't use and that are not exposed
> to L1.  Not sure it's worthwhile though as many of the bits fall into a grey area,
> e.g. all the SMM stuff isn't technically used by KVM, but that's largely because
> much of it just isn't relevant to virtualization.
>
> I'm totally ok leaving it as-is, though maybe name it "unsanitized_misc" or so
> to make that obvious?

I couldn't convince myself to add 'unsanitized_' prefix as I don't think
it significantly reduces possible confusion (the quiestion would be
'sanitized for what and in which way?') so a need for 'git grep' seems
imminent anyway. Hope I've addressed the rest of your comments in v5
though, thanks for your review!

-- 
Vitaly