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[88.115.161.74]) by smtp.gmail.com with ESMTPSA id p17-20020a2eb991000000b00295b1ad177csm1656830ljp.68.2023.03.01.16.02.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 01 Mar 2023 16:02:48 -0800 (PST) Date: Thu, 2 Mar 2023 02:02:45 +0200 From: Zhi Wang To: Michael Roth Cc: , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , Dionna Glaze Subject: Re: [PATCH RFC v8 54/56] x86/sev: Add KVM commands for instance certs Message-ID: <20230302020245.00006f57@gmail.com> In-Reply-To: <20230220183847.59159-55-michael.roth@amd.com> References: <20230220183847.59159-1-michael.roth@amd.com> <20230220183847.59159-55-michael.roth@amd.com> X-Mailer: Claws Mail 4.1.0 (GTK 3.24.33; x86_64-w64-mingw32) Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Mon, 20 Feb 2023 12:38:45 -0600 Michael Roth wrote: In the host-wide certificates installing/uninstalling, a lock is to prevent the racing between cert upload/download path and the handling of guest request path. Guess we need a similar lock to prevent the racing between snp_{set,get}_instance_certs() and snp_handle_ext_guest_request(). This patch and PATCH 27 are focusing on cert from different sources. It would be better to abstract. With the functions and data structure of cert, the cert installing/uninstalling, checks, expectation of the output buffer can be unified. Then we don't need mostly duplicate routines in two different paths. > From: Dionna Glaze > > The /dev/sev device has the ability to store host-wide certificates for > the key used by the AMD-SP for SEV-SNP attestation report signing, > but for hosts that want to specify additional certificates that are > specific to the image launched in a VM, a different way is needed to > communicate those certificates. > > Add two new KVM ioctl to handle this: KVM_SEV_SNP_{GET,SET}_CERTS > > The certificates that are set with this command are expected to follow > the same format as the host certificates, but that format is opaque > to the kernel. > > The new behavior for custom certificates is that the extended guest > request command will now return the overridden certificates if they > were installed for the instance. The error condition for a too small > data buffer is changed to return the overridden certificate data size > if there is an overridden certificate set installed. > > Setting a 0 length certificate returns the system state to only return > the host certificates on an extended guest request. > > Also increase the SEV_FW_BLOB_MAX_SIZE another 4K page to allow space > for an extra certificate. > > Cc: Tom Lendacky > Cc: Paolo Bonzini > > Signed-off-by: Dionna Glaze > Signed-off-by: Ashish Kalra > [mdr: remove used of "we" and "this patch" in commit log] > Signed-off-by: Michael Roth > --- > arch/x86/kvm/svm/sev.c | 111 ++++++++++++++++++++++++++++++++++++++- > arch/x86/kvm/svm/svm.h | 1 + > include/linux/psp-sev.h | 2 +- > include/uapi/linux/kvm.h | 12 +++++ > 4 files changed, 123 insertions(+), 3 deletions(-) > > diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c > index 70d5650d8d95..18b64b7005e7 100644 > --- a/arch/x86/kvm/svm/sev.c > +++ b/arch/x86/kvm/svm/sev.c > @@ -2089,6 +2089,7 @@ static void *snp_context_create(struct kvm *kvm, struct kvm_sev_cmd *argp) > goto e_free; > > sev->snp_certs_data = certs_data; > + sev->snp_certs_len = 0; > > return context; > Better to move the fix to PATCH 45. > @@ -2404,6 +2405,86 @@ static int snp_launch_finish(struct kvm *kvm, struct kvm_sev_cmd *argp) > return ret; > } > > +static int snp_get_instance_certs(struct kvm *kvm, struct kvm_sev_cmd *argp) > +{ > + struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info; > + struct kvm_sev_snp_get_certs params; > + > + if (!sev_snp_guest(kvm)) > + return -ENOTTY; > + > + if (!sev->snp_context) > + return -EINVAL; > + > + if (copy_from_user(¶ms, (void __user *)(uintptr_t)argp->data, > + sizeof(params))) > + return -EFAULT; > + > + /* No instance certs set. */ > + if (!sev->snp_certs_len) > + return -ENOENT; > + > + if (params.certs_len < sev->snp_certs_len) { > + /* Output buffer too small. Return the required size. */ > + params.certs_len = sev->snp_certs_len; > + > + if (copy_to_user((void __user *)(uintptr_t)argp->data, ¶ms, > + sizeof(params))) > + return -EFAULT; > + > + return -EINVAL; > + } > + > + if (copy_to_user((void __user *)(uintptr_t)params.certs_uaddr, > + sev->snp_certs_data, sev->snp_certs_len)) > + return -EFAULT; > + > + return 0; > +} > + > +static int snp_set_instance_certs(struct kvm *kvm, struct kvm_sev_cmd *argp) > +{ > + struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info; > + unsigned long length = SEV_FW_BLOB_MAX_SIZE; > + void *to_certs = sev->snp_certs_data; > + struct kvm_sev_snp_set_certs params; > + > + if (!sev_snp_guest(kvm)) > + return -ENOTTY; > + > + if (!sev->snp_context) > + return -EINVAL; > + > + if (copy_from_user(¶ms, (void __user *)(uintptr_t)argp->data, > + sizeof(params))) > + return -EFAULT; > + > + if (params.certs_len > SEV_FW_BLOB_MAX_SIZE) > + return -EINVAL; > + > + /* > + * Setting a length of 0 is the same as "uninstalling" instance- > + * specific certificates. > + */ > + if (params.certs_len == 0) { > + sev->snp_certs_len = 0; > + return 0; > + } > + > + /* Page-align the length */ > + length = (params.certs_len + PAGE_SIZE - 1) & PAGE_MASK; > + > + if (copy_from_user(to_certs, > + (void __user *)(uintptr_t)params.certs_uaddr, > + params.certs_len)) { > + return -EFAULT; > + } > + > + sev->snp_certs_len = length; > + > + return 0; > +} > + > int sev_mem_enc_ioctl(struct kvm *kvm, void __user *argp) > { > struct kvm_sev_cmd sev_cmd; > @@ -2503,6 +2584,12 @@ int sev_mem_enc_ioctl(struct kvm *kvm, void __user *argp) > case KVM_SEV_SNP_LAUNCH_FINISH: > r = snp_launch_finish(kvm, &sev_cmd); > break; > + case KVM_SEV_SNP_GET_CERTS: > + r = snp_get_instance_certs(kvm, &sev_cmd); > + break; > + case KVM_SEV_SNP_SET_CERTS: > + r = snp_set_instance_certs(kvm, &sev_cmd); > + break; > default: > r = -EINVAL; > goto out; > @@ -3550,8 +3637,28 @@ static void snp_handle_ext_guest_request(struct vcpu_svm *svm, gpa_t req_gpa, gp > if (rc) > goto unlock; > > - rc = snp_guest_ext_guest_request(&req, (unsigned long)sev->snp_certs_data, > - &data_npages, &err); > + /* > + * If the VMM has overridden the certs, then change the error message > + * if the size is inappropriate for the override. Otherwise, use a > + * regular guest request and copy back the instance certs. > + */ > + if (sev->snp_certs_len) { > + if ((data_npages << PAGE_SHIFT) < sev->snp_certs_len) { > + rc = -EINVAL; > + err = SNP_GUEST_REQ_INVALID_LEN; > + goto datalen; > + } > + rc = sev_issue_cmd(kvm, SEV_CMD_SNP_GUEST_REQUEST, &req, > + (int *)&err); > + } else { > + rc = snp_guest_ext_guest_request(&req, > + (unsigned long)sev->snp_certs_data, > + &data_npages, &err); > + } > +datalen: > + if (sev->snp_certs_len) > + data_npages = sev->snp_certs_len >> PAGE_SHIFT; > + > if (rc) { > /* > * If buffer length is small then return the expected > diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h > index 221b38d3c845..dced46559508 100644 > --- a/arch/x86/kvm/svm/svm.h > +++ b/arch/x86/kvm/svm/svm.h > @@ -94,6 +94,7 @@ struct kvm_sev_info { > u64 snp_init_flags; > void *snp_context; /* SNP guest context page */ > void *snp_certs_data; > + unsigned int snp_certs_len; /* Size of instance override for certs */ > struct mutex guest_req_lock; /* Lock for guest request handling */ > > u64 sev_features; /* Features set at VMSA creation */ > diff --git a/include/linux/psp-sev.h b/include/linux/psp-sev.h > index 92116e2b74fd..3b28b78938f6 100644 > --- a/include/linux/psp-sev.h > +++ b/include/linux/psp-sev.h > @@ -22,7 +22,7 @@ > #define __psp_pa(x) __pa(x) > #endif > > -#define SEV_FW_BLOB_MAX_SIZE 0x4000 /* 16KB */ > +#define SEV_FW_BLOB_MAX_SIZE 0x5000 /* 20KB */ > > /** > * SEV platform state > diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h > index 6e684bf5f723..ad7e24e43547 100644 > --- a/include/uapi/linux/kvm.h > +++ b/include/uapi/linux/kvm.h > @@ -1928,6 +1928,8 @@ enum sev_cmd_id { > KVM_SEV_SNP_LAUNCH_START, > KVM_SEV_SNP_LAUNCH_UPDATE, > KVM_SEV_SNP_LAUNCH_FINISH, > + KVM_SEV_SNP_GET_CERTS, > + KVM_SEV_SNP_SET_CERTS, > > KVM_SEV_NR_MAX, > }; > @@ -2075,6 +2077,16 @@ struct kvm_sev_snp_launch_finish { > __u8 pad[6]; > }; > > +struct kvm_sev_snp_get_certs { > + __u64 certs_uaddr; > + __u64 certs_len; > +}; > + > +struct kvm_sev_snp_set_certs { > + __u64 certs_uaddr; > + __u64 certs_len; > +}; > + > #define KVM_DEV_ASSIGN_ENABLE_IOMMU (1 << 0) > #define KVM_DEV_ASSIGN_PCI_2_3 (1 << 1) > #define KVM_DEV_ASSIGN_MASK_INTX (1 << 2)