Re: [PATCH v6 01/14] KVM: SVM: Add KVM_SEV SEND_START command

From: Krish Sadhukhan
Date: Thu Apr 02 2020 - 13:52:31 EST


On 3/29/20 11:19 PM, 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: "Radim KrÄmÃÅ" <rkrcmar@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>
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.c | 128 ++++++++++++++++++
include/linux/psp-sev.h | 8 +-
include/uapi/linux/kvm.h | 12 ++
4 files changed, 171 insertions(+), 4 deletions(-)

diff --git a/Documentation/virt/kvm/amd-memory-encryption.rst b/Documentation/virt/kvm/amd-memory-encryption.rst
index c3129b9ba5cb..4fd34fc5c7a7 100644
--- a/Documentation/virt/kvm/amd-memory-encryption.rst
+++ b/Documentation/virt/kvm/amd-memory-encryption.rst
@@ -263,6 +263,33 @@ Returns: 0 on success, -negative on error
__u32 trans_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.
Shouldn't we mention that this command is also used to save the guest to the disk ?
+
+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_uadr; /* platform certificate chain */
+ __u32 plat_certs_len;
+
+ __u64 amd_certs_uaddr; /* AMD certificate */
+ __u32 amd_cert_len;
+
+ __u64 session_uaddr; /* Guest session information */
+ __u32 session_len;
+ };
+
References
==========
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 50d1ebafe0b3..63d172e974ad 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -7149,6 +7149,131 @@ static int sev_launch_secret(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,


__sev_query_send_start_session_length a better name perhaps ?

+ 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);


We are not checking ret here as we are assuming that the command will always be successful. Is there any chance that sev->handle can be junk and should we have an ASSERT for it ?

+
+ 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)


For readability and ease of cscope searches, isn't it better to append "svm" to all these functions ?

It seems svm_sev_enabled() is an example of an appropriate naming style.

+{
+ 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;


What if params.plat_certs_uaddr or params.amd_certs_uaddr is NULL ?

+
+ /* 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 */


You haven't added comments for plat_cert and amd_cert. Also, it's much more readable if you add block comments like,

ÂÂÂ ÂÂÂ /*

ÂÂÂÂÂÂÂÂ *Â PDH cert

ÂÂÂ ÂÂÂÂ */

+ 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)
+ goto e_free;
+
+ if (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;
+}
+
static int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
{
struct kvm_sev_cmd sev_cmd;
@@ -7193,6 +7318,9 @@ static int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
case KVM_SEV_LAUNCH_SECRET:
r = sev_launch_secret(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 5167bf2bfc75..9f63b9d48b63 100644
--- a/include/linux/psp-sev.h
+++ b/include/linux/psp-sev.h
@@ -323,11 +323,11 @@ 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 */


It seems that the 'platform certificate' and the 'amd_certificate' are single entities, meaning only copy is there for the particular platform and particular the AMD product. Why are these plural then ?


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 4b95f9a31a2f..17bef4c245e1 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1558,6 +1558,18 @@ struct kvm_sev_dbg {
__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)