Re: [PATCH v13 01/12] KVM: SVM: Add KVM_SEV SEND_START command

Paolo Bonzini
2021-04-20T08:50:19Z

On 15/04/21 17:53, Ashish Kalra wrote:
> From: Brijesh Singh <brijesh.singh@amd.com>
>
> The command is used to create an outgoing SEV guest encryption context.
>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Joerg Roedel <joro@8bytes.org>
> Cc: Borislav Petkov <bp@suse.de>
> Cc: Tom Lendacky <thomas.lendacky@amd.com>
> Cc: x86@kernel.org
> Cc: kvm@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> Reviewed-by: Steve Rutherford <srutherford@google.com>
> Reviewed-by: Venu Busireddy <venu.busireddy@oracle.com>
> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
> Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
> ---
> .../virt/kvm/amd-memory-encryption.rst | 27 ++++
> arch/x86/kvm/svm/sev.c | 125 ++++++++++++++++++
> include/linux/psp-sev.h | 8 +-
> include/uapi/linux/kvm.h | 12 ++
> 4 files changed, 168 insertions(+), 4 deletions(-)
>
> diff --git a/Documentation/virt/kvm/amd-memory-encryption.rst b/Documentation/virt/kvm/amd-memory-encryption.rst
> index 469a6308765b..ac799dd7a618 100644
> --- a/Documentation/virt/kvm/amd-memory-encryption.rst
> +++ b/Documentation/virt/kvm/amd-memory-encryption.rst
> @@ -284,6 +284,33 @@ Returns: 0 on success, -negative on error
> __u32 len;
> };
>
> +10. KVM_SEV_SEND_START
> +----------------------
> +
> +The KVM_SEV_SEND_START command can be used by the hypervisor to create an
> +outgoing guest encryption context.
> +
> +Parameters (in): struct kvm_sev_send_start
> +
> +Returns: 0 on success, -negative on error
> +
> +::
> + struct kvm_sev_send_start {
> + __u32 policy; /* guest policy */
> +
> + __u64 pdh_cert_uaddr; /* platform Diffie-Hellman certificate */
> + __u32 pdh_cert_len;
> +
> + __u64 plat_certs_uaddr; /* platform certificate chain */
> + __u32 plat_certs_len;
> +
> + __u64 amd_certs_uaddr; /* AMD certificate */
> + __u32 amd_certs_len;
> +
> + __u64 session_uaddr; /* Guest session information */
> + __u32 session_len;
> + };
> +
> References
> ==========
>
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index 874ea309279f..2b65900c05d6 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -1110,6 +1110,128 @@ static int sev_get_attestation_report(struct kvm *kvm, struct kvm_sev_cmd *argp)
> return ret;
> }
>
> +/* Userspace wants to query session length. */
> +static int
> +__sev_send_start_query_session_length(struct kvm *kvm, struct kvm_sev_cmd *argp,
> + struct kvm_sev_send_start *params)
> +{
> + struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
> + struct sev_data_send_start *data;
> + int ret;
> +
> + data = kzalloc(sizeof(*data), GFP_KERNEL_ACCOUNT);
> + if (data == NULL)
> + return -ENOMEM;
> +
> + data->handle = sev->handle;
> + ret = sev_issue_cmd(kvm, SEV_CMD_SEND_START, data, &argp->error);

This is missing an "if (ret < 0)" (and this time I'm pretty sure it's
indeed the case :)), otherwise you miss for example the EBADF return
code if the SEV file descriptor is closed or reused. Same for
KVM_SEND_UPDATE_DATA. Also, the length==0 case is not documented.

Paolo

> + params->session_len = data->session_len;
> + if (copy_to_user((void __user *)(uintptr_t)argp->data, params,
> + sizeof(struct kvm_sev_send_start)))
> + ret = -EFAULT;
> +
> + kfree(data);
> + return ret;
> +}
> +
> +static int sev_send_start(struct kvm *kvm, struct kvm_sev_cmd *argp)
> +{
> + struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
> + struct sev_data_send_start *data;
> + struct kvm_sev_send_start params;
> + void *amd_certs, *session_data;
> + void *pdh_cert, *plat_certs;
> + int ret;
> +
> + if (!sev_guest(kvm))
> + return -ENOTTY;
> +
> + if (copy_from_user(&params, (void __user *)(uintptr_t)argp->data,
> + sizeof(struct kvm_sev_send_start)))
> + return -EFAULT;
> +
> + /* if session_len is zero, userspace wants to query the session length */
> + if (!params.session_len)
> + return __sev_send_start_query_session_length(kvm, argp,
> + &params);
> +
> + /* some sanity checks */
> + if (!params.pdh_cert_uaddr || !params.pdh_cert_len ||
> + !params.session_uaddr || params.session_len > SEV_FW_BLOB_MAX_SIZE)
> + return -EINVAL;
> +
> + /* allocate the memory to hold the session data blob */
> + session_data = kmalloc(params.session_len, GFP_KERNEL_ACCOUNT);
> + if (!session_data)
> + return -ENOMEM;
> +
> + /* copy the certificate blobs from userspace */
> + pdh_cert = psp_copy_user_blob(params.pdh_cert_uaddr,
> + params.pdh_cert_len);
> + if (IS_ERR(pdh_cert)) {
> + ret = PTR_ERR(pdh_cert);
> + goto e_free_session;
> + }
> +
> + plat_certs = psp_copy_user_blob(params.plat_certs_uaddr,
> + params.plat_certs_len);
> + if (IS_ERR(plat_certs)) {
> + ret = PTR_ERR(plat_certs);
> + goto e_free_pdh;
> + }
> +
> + amd_certs = psp_copy_user_blob(params.amd_certs_uaddr,
> + params.amd_certs_len);
> + if (IS_ERR(amd_certs)) {
> + ret = PTR_ERR(amd_certs);
> + goto e_free_plat_cert;
> + }
> +
> + data = kzalloc(sizeof(*data), GFP_KERNEL_ACCOUNT);
> + if (data == NULL) {
> + ret = -ENOMEM;
> + goto e_free_amd_cert;
> + }
> +
> + /* populate the FW SEND_START field with system physical address */
> + data->pdh_cert_address = __psp_pa(pdh_cert);
> + data->pdh_cert_len = params.pdh_cert_len;
> + data->plat_certs_address = __psp_pa(plat_certs);
> + data->plat_certs_len = params.plat_certs_len;
> + data->amd_certs_address = __psp_pa(amd_certs);
> + data->amd_certs_len = params.amd_certs_len;
> + data->session_address = __psp_pa(session_data);
> + data->session_len = params.session_len;
> + data->handle = sev->handle;
> +
> + ret = sev_issue_cmd(kvm, SEV_CMD_SEND_START, data, &argp->error);
> +
> + if (!ret && copy_to_user((void __user *)(uintptr_t)params.session_uaddr,
> + session_data, params.session_len)) {
> + ret = -EFAULT;
> + goto e_free;
> + }
> +
> + params.policy = data->policy;
> + params.session_len = data->session_len;
> + if (copy_to_user((void __user *)(uintptr_t)argp->data, &params,
> + sizeof(struct kvm_sev_send_start)))
> + ret = -EFAULT;
> +
> +e_free:
> + kfree(data);
> +e_free_amd_cert:
> + kfree(amd_certs);
> +e_free_plat_cert:
> + kfree(plat_certs);
> +e_free_pdh:
> + kfree(pdh_cert);
> +e_free_session:
> + kfree(session_data);
> + return ret;
> +}
> +
> int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
> {
> struct kvm_sev_cmd sev_cmd;
> @@ -1163,6 +1285,9 @@ int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
> case KVM_SEV_GET_ATTESTATION_REPORT:
> r = sev_get_attestation_report(kvm, &sev_cmd);
> break;
> + case KVM_SEV_SEND_START:
> + r = sev_send_start(kvm, &sev_cmd);
> + break;
> default:
> r = -EINVAL;
> goto out;
> diff --git a/include/linux/psp-sev.h b/include/linux/psp-sev.h
> index b801ead1e2bb..73da511b9423 100644
> --- a/include/linux/psp-sev.h
> +++ b/include/linux/psp-sev.h
> @@ -326,11 +326,11 @@ struct sev_data_send_start {
> u64 pdh_cert_address; /* In */
> u32 pdh_cert_len; /* In */
> u32 reserved1;
> - u64 plat_cert_address; /* In */
> - u32 plat_cert_len; /* In */
> + u64 plat_certs_address; /* In */
> + u32 plat_certs_len; /* In */
> u32 reserved2;
> - u64 amd_cert_address; /* In */
> - u32 amd_cert_len; /* In */
> + u64 amd_certs_address; /* In */
> + u32 amd_certs_len; /* In */
> u32 reserved3;
> u64 session_address; /* In */
> u32 session_len; /* In/Out */
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index f6afee209620..ac53ad2e7271 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -1729,6 +1729,18 @@ struct kvm_sev_attestation_report {
> __u32 len;
> };
>
> +struct kvm_sev_send_start {
> + __u32 policy;
> + __u64 pdh_cert_uaddr;
> + __u32 pdh_cert_len;
> + __u64 plat_certs_uaddr;
> + __u32 plat_certs_len;
> + __u64 amd_certs_uaddr;
> + __u32 amd_certs_len;
> + __u64 session_uaddr;
> + __u32 session_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)
>