linux-kernel - Re: [PATCH v5 10/23] KVM: VMX: Add support for FRED context save/restore

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Message-ID: <5a001c2b-eb59-487e-bf4a-0447af42829c@zytor.com>
Date: Thu, 24 Jul 2025 11:01:26 -0700
From: Xin Li <xin@...or.com>
To: Chao Gao <chao.gao@...el.com>
Cc: linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        linux-doc@...r.kernel.org, pbonzini@...hat.com, seanjc@...gle.com,
        corbet@....net, tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com,
        luto@...nel.org, peterz@...radead.org, andrew.cooper3@...rix.com,
        hch@...radead.org
Subject: Re: [PATCH v5 10/23] KVM: VMX: Add support for FRED context
 save/restore

On 7/23/2025 10:35 PM, Chao Gao wrote:
> Return KVM_MSR_RET_UNSUPPORTED instead of 1.
> 
> KVM's uAPI allows userspace to read MSRs and write 0 to MSRs even if an MSR
> isn't supported according to guest CPUIDs. Returning KVM_MSR_RET_UNSUPPORTED
> allows kvm_do_msr_access() to suppress the failure when needed to comply with
> the uAPI.
> 
> For more details, see kvm_do_msr_access().

You're right; I missed the API improvement.

Thanks!
     Xin