[PATCH Part2 RFC v3 23/37] KVM: SVM: Add KVM_SEV_SNP_LAUNCH_FINISH command

Brijesh Singh
2021-06-02T14:14:22Z

The KVM_SEV_SNP_LAUNCH_FINISH finalize the cryptographic digest and stores
it as the measurement of the guest at launch.

While finalizing the launch flow, it also issues the LAUNCH_UPDATE command
to encrypt the VMSA pages.

Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
arch/x86/kvm/svm/sev.c | 125 +++++++++++++++++++++++++++++++++++++++
include/uapi/linux/kvm.h | 13 ++++
2 files changed, 138 insertions(+)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 6b7c8287eada..856a6cf99a61 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -1741,6 +1741,111 @@ static int snp_launch_update(struct kvm *kvm, struct kvm_sev_cmd *argp)
return ret;
}

+static int snp_launch_update_vmsa(struct kvm *kvm, struct kvm_sev_cmd *argp)
+{
+ struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
+ struct sev_data_snp_launch_update data = {};
+ int i, ret;
+
+ data.gctx_paddr = __psp_pa(sev->snp_context);
+ data.page_type = SNP_PAGE_TYPE_VMSA;
+
+ for (i = 0; i < kvm->created_vcpus; i++) {
+ struct vcpu_svm *svm = to_svm(kvm->vcpus[i]);
+ struct rmpupdate e = {};
+
+ /* Perform some pre-encryption checks against the VMSA */
+ ret = sev_es_sync_vmsa(svm);
+ if (ret)
+ return ret;
+
+ /* Transition the VMSA page to a firmware state. */
+ e.assigned = 1;
+ e.immutable = 1;
+ e.asid = sev->asid;
+ e.gpa = -1;
+ e.pagesize = RMP_PG_SIZE_4K;
+ ret = rmpupdate(virt_to_page(svm->vmsa), &e);
+ if (ret)
+ return ret;
+
+ /* Issue the SNP command to encrypt the VMSA */
+ data.address = __sme_pa(svm->vmsa);
+ ret = __sev_issue_cmd(argp->sev_fd, SEV_CMD_SNP_LAUNCH_UPDATE,
+ &data, &argp->error);
+ if (ret) {
+ snp_page_reclaim(virt_to_page(svm->vmsa), RMP_PG_SIZE_4K);
+ return ret;
+ }
+
+ svm->vcpu.arch.guest_state_protected = true;
+ }
+
+ return 0;
+}
+
+static int snp_launch_finish(struct kvm *kvm, struct kvm_sev_cmd *argp)
+{
+ struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
+ struct sev_data_snp_launch_finish *data;
+ void *id_block = NULL, *id_auth = NULL;
+ struct kvm_sev_snp_launch_finish params;
+ int ret;
+
+ if (!sev_snp_guest(kvm))
+ return -ENOTTY;
+
+ if (!sev->snp_context)
+ return -EINVAL;
+
+ if (copy_from_user(&params, (void __user *)(uintptr_t)argp->data, sizeof(params)))
+ return -EFAULT;
+
+ /* Measure all vCPUs using LAUNCH_UPDATE before we finalize the launch flow. */
+ ret = snp_launch_update_vmsa(kvm, argp);
+ if (ret)
+ return ret;
+
+ data = kzalloc(sizeof(*data), GFP_KERNEL_ACCOUNT);
+ if (!data)
+ return -ENOMEM;
+
+ if (params.id_block_en) {
+ id_block = psp_copy_user_blob(params.id_block_uaddr, KVM_SEV_SNP_ID_BLOCK_SIZE);
+ if (IS_ERR(id_block)) {
+ ret = PTR_ERR(id_block);
+ goto e_free;
+ }
+
+ data->id_block_en = 1;
+ data->id_block_paddr = __sme_pa(id_block);
+ }
+
+ if (params.auth_key_en) {
+ id_auth = psp_copy_user_blob(params.id_auth_uaddr, KVM_SEV_SNP_ID_AUTH_SIZE);
+ if (IS_ERR(id_auth)) {
+ ret = PTR_ERR(id_auth);
+ goto e_free_id_block;
+ }
+
+ data->auth_key_en = 1;
+ data->id_auth_paddr = __sme_pa(id_auth);
+ }
+
+ data->gctx_paddr = __psp_pa(sev->snp_context);
+ ret = sev_issue_cmd(kvm, SEV_CMD_SNP_LAUNCH_FINISH, data, &argp->error);
+
+ kfree(id_auth);
+
+e_free_id_block:
+ kfree(id_block);
+
+e_free:
+ kfree(data);
+
+ return ret;
+}
+
int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
{
struct kvm_sev_cmd sev_cmd;
@@ -1836,6 +1941,9 @@ int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
case KVM_SEV_SNP_LAUNCH_UPDATE:
r = snp_launch_update(kvm, &sev_cmd);
break;
+ case KVM_SEV_SNP_LAUNCH_FINISH:
+ r = snp_launch_finish(kvm, &sev_cmd);
+ break;
default:
r = -EINVAL;
goto out;
@@ -2324,8 +2432,25 @@ void sev_free_vcpu(struct kvm_vcpu *vcpu)

if (vcpu->arch.guest_state_protected)
sev_flush_guest_memory(svm, svm->vmsa, PAGE_SIZE);
+
+ /*
+ * If its an SNP guest, then VMSA was added in the RMP entry as a guest owned page.
+ * Transition the page to hyperivosr state before releasing it back to the system.
+ */
+ if (sev_snp_guest(vcpu->kvm)) {
+ struct rmpupdate e = {};
+ int rc;
+
+ rc = rmpupdate(virt_to_page(svm->vmsa), &e);
+ if (rc) {
+ pr_err("Failed to release SNP guest VMSA page (rc %d), leaking it\n", rc);
+ goto skip_vmsa_free;
+ }
+ }
+
__free_page(virt_to_page(svm->vmsa));

+skip_vmsa_free:
if (svm->ghcb_sa_free)
kfree(svm->ghcb_sa);
}
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 8890d5a340be..8db12055b8b9 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1682,6 +1682,7 @@ enum sev_cmd_id {
KVM_SEV_SNP_INIT = 255,
KVM_SEV_SNP_LAUNCH_START,
KVM_SEV_SNP_LAUNCH_UPDATE,
+ KVM_SEV_SNP_LAUNCH_FINISH,

KVM_SEV_NR_MAX,
};
@@ -1693,6 +1694,18 @@ struct kvm_sev_cmd {
__u32 sev_fd;
};

+#define KVM_SEV_SNP_ID_BLOCK_SIZE 96
+#define KVM_SEV_SNP_ID_AUTH_SIZE 4096
+#define KVM_SEV_SNP_FINISH_DATA_SIZE 32
+
+struct kvm_sev_snp_launch_finish {
+ __u64 id_block_uaddr;
+ __u64 id_auth_uaddr;
+ __u8 id_block_en;
+ __u8 auth_key_en;
+ __u8 host_data[KVM_SEV_SNP_FINISH_DATA_SIZE];
+};
+
struct kvm_sev_launch_start {
__u32 handle;
__u32 policy;
--
2.17.1