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AJvYcCUAUASocdsImsC+9uHq9uRajDQfpDyvvUvu0TITDm+VxN7tTEVtGTvdWBsSfSWcS9312gJd8TJp4HbJDJ66tIy8nisdnGsFnclyIg== X-Gm-Message-State: AOJu0Yzfm7UYSTglw05Iamq8K7kCyUlr3ivAgLlwig3xwXq+JD9+uNo3 Ey57eFfWbBGsAmaUwWB69dDkYTH0XuZK8oQQaVUQSBIa2TuhGbKPxDJ3vWp+5jhROIyDiwp6z6x GOA== X-Google-Smtp-Source: AGHT+IHoLpy1haJfmM+o0LmD5U1iZh86EBvuJ5rgP0o2pdMh09BBK9/6PtMelrlOW3VGdks0UySW+x/E2qQ= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a17:90a:e7c4:b0:2c2:c6fa:c05d with SMTP id 98e67ed59e1d1-2c86147a695mr30306a91.9.1719412353662; Wed, 26 Jun 2024 07:32:33 -0700 (PDT) Date: Wed, 26 Jun 2024 07:32:32 -0700 In-Reply-To: <20240621171519.3180965-1-michael.roth@amd.com> Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240621134041.3170480-2-michael.roth@amd.com> <20240621171519.3180965-1-michael.roth@amd.com> Message-ID: Subject: Re: [PATCH v1-revised 1/5] KVM: SEV: Provide support for SNP_GUEST_REQUEST NAE event From: Sean Christopherson To: Michael Roth Cc: kvm@vger.kernel.org, linux-coco@lists.linux.dev, linux-kernel@vger.kernel.org, x86@kernel.org, pbonzini@redhat.com, jroedel@suse.de, thomas.lendacky@amd.com, pgonda@google.com, ashish.kalra@amd.com, bp@alien8.de, pankaj.gupta@amd.com, liam.merwick@oracle.com, Brijesh Singh , Alexey Kardashevskiy Content-Type: text/plain; charset="us-ascii" On Fri, Jun 21, 2024, Michael Roth wrote: > diff --git a/include/uapi/linux/sev-guest.h b/include/uapi/linux/sev-guest.h > index 154a87a1eca9..7bd78e258569 100644 > --- a/include/uapi/linux/sev-guest.h > +++ b/include/uapi/linux/sev-guest.h > @@ -89,8 +89,17 @@ struct snp_ext_report_req { > #define SNP_GUEST_FW_ERR_MASK GENMASK_ULL(31, 0) > #define SNP_GUEST_VMM_ERR_SHIFT 32 > #define SNP_GUEST_VMM_ERR(x) (((u64)x) << SNP_GUEST_VMM_ERR_SHIFT) > +#define SNP_GUEST_FW_ERR(x) ((x) & SNP_GUEST_FW_ERR_MASK) > +#define SNP_GUEST_ERR(vmm_err, fw_err) (SNP_GUEST_VMM_ERR(vmm_err) | \ > + SNP_GUEST_FW_ERR(fw_err)) > > +/* > + * The GHCB spec only formally defines INVALID_LEN/BUSY VMM errors, but define > + * a GENERIC error code such that it won't ever conflict with GHCB-defined > + * errors if any get added in the future. > + */ > #define SNP_GUEST_VMM_ERR_INVALID_LEN 1 > #define SNP_GUEST_VMM_ERR_BUSY 2 > +#define SNP_GUEST_VMM_ERR_GENERIC BIT(31) Related to my suggestion to not have KVM-defined error codes, if we go that route, then I believe SNP_GUEST_VMM_ERR_GENERIC is unnecessary. For snp_handle_guest_req(), if sev_issue_cmd() fails, KVM can/should do something like: /* Forward non-firmware errors to userspace, e.g. if the PSP is dead. */ if (ret && !fw_err) goto release_req; ghcb_set_sw_exit_info_2(svm->sev_es.ghcb, SNP_GUEST_ERR(0, fw_err)); And then in snp_complete_req_certs(), we could either let userspace shove in any error code whatsoever, or restrict userspace to known, GHCB-defined error codes, e.g. int err; err = READ_ONCE(vcpu->run->coco.req_certs.ret); if (err) if (err != SNP_GUEST_VMM_ERR_INVALID_LEN && err != SNP_GUEST_VMM_ERR_BUSY) return -EINVAL; if (err == SNP_GUEST_VMM_ERR_INVALID_LEN) vcpu->arch.regs[VCPU_REGS_RBX] = vcpu->run->coco.req_certs.npages; ghcb_set_sw_exit_info_2(svm->sev_es.ghcb, SNP_GUEST_ERR(err, 0)); return 1; } > > #endif /* __UAPI_LINUX_SEV_GUEST_H_ */ > -- > 2.25.1 >