Messages in this thread | | | Date | Fri, 21 Oct 2022 14:06:36 -0500 | Subject | Re: [PATCH Part2 v6 42/49] KVM: SVM: Provide support for SNP_GUEST_REQUEST NAE event | From | Tom Lendacky <> |
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On 6/20/22 18:13, Ashish Kalra wrote: > From: Brijesh Singh <brijesh.singh@amd.com> > > Version 2 of GHCB specification added the support for two SNP Guest > Request Message NAE events. The events allows for an SEV-SNP guest to > make request to the SEV-SNP firmware through hypervisor using the > SNP_GUEST_REQUEST API define in the SEV-SNP firmware specification. > > The SNP_EXT_GUEST_REQUEST is similar to SNP_GUEST_REQUEST with the > difference of an additional certificate blob that can be passed through > the SNP_SET_CONFIG ioctl defined in the CCP driver. The CCP driver > provides snp_guest_ext_guest_request() that is used by the KVM to get > both the report and certificate data at once. > > Signed-off-by: Brijesh Singh <brijesh.singh@amd.com> > --- > arch/x86/kvm/svm/sev.c | 196 +++++++++++++++++++++++++++++++++++++++-- > arch/x86/kvm/svm/svm.h | 2 + > 2 files changed, 192 insertions(+), 6 deletions(-) > > diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c > index 7fc0fad87054..089af21a4efe 100644 > --- a/arch/x86/kvm/svm/sev.c > +++ b/arch/x86/kvm/svm/sev.c
> +static void snp_handle_ext_guest_request(struct vcpu_svm *svm, gpa_t req_gpa, gpa_t resp_gpa) > +{ > + struct sev_data_snp_guest_request req = {0}; > + struct kvm_vcpu *vcpu = &svm->vcpu; > + struct kvm *kvm = vcpu->kvm; > + unsigned long data_npages; > + struct kvm_sev_info *sev; > + unsigned long rc, err; > + u64 data_gpa; > + > + if (!sev_snp_guest(vcpu->kvm)) { > + rc = SEV_RET_INVALID_GUEST; > + goto e_fail; > + } > + > + sev = &to_kvm_svm(kvm)->sev_info; > + > + data_gpa = vcpu->arch.regs[VCPU_REGS_RAX]; > + data_npages = vcpu->arch.regs[VCPU_REGS_RBX]; > + > + if (!IS_ALIGNED(data_gpa, PAGE_SIZE)) { > + rc = SEV_RET_INVALID_ADDRESS; > + goto e_fail; > + } > + > + /* Verify that requested blob will fit in certificate buffer */ > + if ((data_npages << PAGE_SHIFT) > SEV_FW_BLOB_MAX_SIZE) {
Not sure this is a valid check... Isn't it OK if the guest has supplied more room than is required? If the guest supplies 8 pages and the hypervisor only needs to copy 1 page of data (or the SEV_FW_BLOB_MAX_SIZE number of pages) that shouldn't be an error. I think this check can go, right?
Thanks, Tom
> + rc = SEV_RET_INVALID_PARAM; > + goto e_fail; > + } > + > + mutex_lock(&sev->guest_req_lock); > + > + rc = snp_setup_guest_buf(svm, &req, req_gpa, resp_gpa); > + if (rc) > + goto unlock; > + > + rc = snp_guest_ext_guest_request(&req, (unsigned long)sev->snp_certs_data, > + &data_npages, &err); > + if (rc) { > + /* > + * If buffer length is small then return the expected > + * length in rbx. > + */ > + if (err == SNP_GUEST_REQ_INVALID_LEN) > + vcpu->arch.regs[VCPU_REGS_RBX] = data_npages; > + > + /* pass the firmware error code */ > + rc = err; > + goto cleanup; > + } > + > + /* Copy the certificate blob in the guest memory */ > + if (data_npages && > + kvm_write_guest(kvm, data_gpa, sev->snp_certs_data, data_npages << PAGE_SHIFT)) > + rc = SEV_RET_INVALID_ADDRESS; > + > +cleanup: > + snp_cleanup_guest_buf(&req, &rc); > + > +unlock: > + mutex_unlock(&sev->guest_req_lock); > + > +e_fail: > + svm_set_ghcb_sw_exit_info_2(vcpu, rc); > +} > +
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