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

From: Paolo Bonzini
Date: Tue Apr 20 2021 - 04:50:20 EST

On 15/04/21 17:53, Ashish Kalra wrote:
From: Brijesh Singh <brijesh.singh@xxxxxxx>

The command is used to create an outgoing SEV guest encryption context.

Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: Joerg Roedel <joro@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxx>
Cc: Tom Lendacky <thomas.lendacky@xxxxxxx>
Cc: x86@xxxxxxxxxx
Cc: kvm@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Reviewed-by: Steve Rutherford <srutherford@xxxxxxxxxx>
Reviewed-by: Venu Busireddy <venu.busireddy@xxxxxxxxxx>
Signed-off-by: Brijesh Singh <brijesh.singh@xxxxxxx>
Signed-off-by: Ashish Kalra <ashish.kalra@xxxxxxx>
---
.../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)