linux-kernel - Re: [PATCH v2 7/8] KVM: SVM: move MSR_IA32_SPEC

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Message-ID: <85d7b64a-cdb0-d63b-ec4a-8d6920071fef@redhat.com>
Date:   Wed, 9 Nov 2022 10:29:59 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        nathan@...nel.org, thomas.lendacky@....com,
        andrew.cooper3@...rix.com, peterz@...radead.org,
        jmattson@...gle.com, stable@...r.kernel.org
Subject: Re: [PATCH v2 7/8] KVM: SVM: move MSR_IA32_SPEC_CTRL save/restore to
 assembly

On 11/9/22 02:14, Sean Christopherson wrote:
>>
>> +.macro RESTORE_SPEC_CTRL_BODY
> 
> Can we split these into separate macros?  It's a bit more typing, but it's not
> immediately obvious that these are two independent chunks (I was expecting a JMP
> from the 800 section into the 900 section).
> 
> E.g. RESTORE_GUEST_SPEC_CTRL_BODY and RESTORE_HOST_SPEC_CTRL_BODY

Sure, I had it like that in an earlier version.  I didn't see much 
benefit but it is indeed a bit more readable if you order the macros like

.macro RESTORE_GUEST_SPEC_CTRL
.macro RESTORE_GUEST_SPEC_CTRL_BODY
.macro RESTORE_HOST_SPEC_CTRL
.macro RESTORE_HOST_SPEC_CTRL_BODY

>> +800:
>
> Ugh, the multiple users makes it somewhat ugly, but rather than arbitrary numbers,
> what about using named labels to make it easier to understand the branches?

I think it's okay if we separate the macros.

Paolo