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Tue, 20 Apr 2021 19:09:53 +0000 Cc: brijesh.singh@amd.com Subject: Re: [PATCH] KVM: x86: document behavior of measurement ioctls with len==0 To: Paolo Bonzini , linux-kernel@vger.kernel.org, kvm@vger.kernel.org References: <20210420093411.1498840-1-pbonzini@redhat.com> From: Brijesh Singh Message-ID: Date: Tue, 20 Apr 2021 14:09:51 -0500 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.9.1 In-Reply-To: <20210420093411.1498840-1-pbonzini@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US X-Originating-IP: [70.112.153.56] X-ClientProxiedBy: SA9PR13CA0164.namprd13.prod.outlook.com (2603:10b6:806:28::19) To SN6PR12MB2718.namprd12.prod.outlook.com (2603:10b6:805:6f::22) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from Brijeshs-MacBook-Pro.local (70.112.153.56) by SA9PR13CA0164.namprd13.prod.outlook.com (2603:10b6:806:28::19) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4065.6 via Frontend Transport; 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Since the guest owner knows the initial contents of the guest at > boot, the measurement can be verified by comparing it to what the guest owner > expects. > > +If len is zero on entry, the measurement blob length is written to len and > +uaddr is unused. > + > Parameters (in): struct kvm_sev_launch_measure > > Returns: 0 on success, -negative on error > @@ -271,6 +274,9 @@ report containing the SHA-256 digest of the guest memory and VMSA passed through > commands and signed with the PEK. The digest returned by the command should match the digest > used by the guest owner with the KVM_SEV_LAUNCH_MEASURE. > > +If len is zero on entry, the measurement blob length is written to len and > +uaddr is unused. > + > Parameters (in): struct kvm_sev_attestation > > Returns: 0 on success, -negative on error