linux-kernel - Re: [PATCH v2 1/4] KVM: SVM: Get rid of *ghcb_msr

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Date:   Thu, 9 Sep 2021 15:22:51 +0200
From:   Joerg Roedel <joro@...tes.org>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Brijesh Singh <brijesh.singh@....com>,
        Tom Lendacky <thomas.lendacky@....com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-coco@...ts.linux.dev,
        Joerg Roedel <jroedel@...e.de>
Subject: Re: [PATCH v2 1/4] KVM: SVM: Get rid of *ghcb_msr_bits() functions

Hi Sean,

On Wed, Sep 01, 2021 at 09:31:52PM +0000, Sean Christopherson wrote:
> On Wed, Sep 01, 2021, Sean Christopherson wrote:
> > 		control->ghcb_gpa = MAKE_GHCB_MSR_RESP(cpuid_reg, cpuid_value);

Made that change, but kept the set_ghcb_msr_cpuid_resp() and renamed it
to ghcb_msr_cpuid_resp(). It now returns the MSR value for the CPUID
response.

I like the keep the more complicated response setters as functions and
not macros for readability.


> 	case GHCB_MSR_SEV_INFO_REQ:
> 		control->ghcb_gpa = GHCB_MSR_SEV_INFO(GHCB_VERSION_MAX,
> 						      GHCB_VERSION_MIN,
> 						      sev_enc_bit));
> 		break;
> 
> and drop set_ghcb_msr() altogether.

Makes sense, I replaced the set_ghcb_msr() calls with the above.

> Side topic, what about renaming control->ghcb_gpa => control->ghcb_msr so that
> the code for the MSR protocol is a bit more self-documenting?  The APM defines
> the field as "Guest physical address of GHCB", so it's not exactly prescribing a
> specific name.

No strong opinion here, I let this up to the AMD engineers to decide. If
we change the name I can add a separate patch for this.

Regards,

	Joerg