Re: [PATCH RFC v7 40/64] KVM: SVM: Add KVM_SEV_SNP_LAUNCH_FINISH command

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Hello Tom,

On 12/19/2022 12:04 PM, Tom Lendacky wrote:
On 12/14/22 13:40, Michael Roth wrote:
From: Brijesh Singh <brijesh.singh@xxxxxxx>

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.

If its an SNP guest, then VMSA was added in the RMP entry as
a guest owned page and also removed from the kernel direct map
so flush it later after it is transitioned back to hypervisor
state and restored in the direct map.

Signed-off-by: Brijesh Singh <brijesh.singh@xxxxxxx>
Signed-off-by: Harald Hoyer <harald@xxxxxxxxxxx>
Signed-off-by: Ashish Kalra <ashish.kalra@xxxxxxx>
Signed-off-by: Michael Roth <michael.roth@xxxxxxx>
---
  .../virt/kvm/x86/amd-memory-encryption.rst    |  22 ++++
  arch/x86/kvm/svm/sev.c                        | 119 ++++++++++++++++++
  include/uapi/linux/kvm.h                      |  14 +++
  3 files changed, 155 insertions(+)

diff --git a/Documentation/virt/kvm/x86/amd-memory-encryption.rst b/Documentation/virt/kvm/x86/amd-memory-encryption.rst
index c94be8e6d657..e4b42aaab1de 100644
--- a/Documentation/virt/kvm/x86/amd-memory-encryption.rst
+++ b/Documentation/virt/kvm/x86/amd-memory-encryption.rst
@@ -513,6 +513,28 @@ Returns: 0 on success, -negative on error
  See the SEV-SNP spec for further details on how to build the VMPL permission
  mask and page type.
+21. KVM_SNP_LAUNCH_FINISH
+-------------------------
+
+After completion of the SNP guest launch flow, the KVM_SNP_LAUNCH_FINISH command can be
+issued to make the guest ready for the execution.
+
+Parameters (in): struct kvm_sev_snp_launch_finish
+
+Returns: 0 on success, -negative on error
+
+::
+
+        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[32];

This is missing the 6 bytes of padding at the end of the struct.


Yes will fix this, the documentation is missing that, the structure defination in include/uapi/linux/kvm.h includes it.

But why do we need this padding ?

+        };
+
+
+See SEV-SNP specification for further details on launch finish input parameters.
  References
  ==========
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 379e61a9226a..6f901545bed9 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -2243,6 +2243,106 @@ static int snp_launch_update(struct kvm *kvm, struct kvm_sev_cmd *argp)
                        snp_launch_update_gfn_handler, argp);
  }
+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(xa_load(&kvm->vcpu_array, i));
+        u64 pfn = __pa(svm->sev_es.vmsa) >> PAGE_SHIFT;
+
+        /* 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. */
+        ret = rmp_make_private(pfn, -1, PG_LEVEL_4K, sev->asid, true);
+        if (ret)
+            return ret;
+
+        /* Issue the SNP command to encrypt the VMSA */
+        data.address = __sme_pa(svm->sev_es.vmsa);
+        ret = __sev_issue_cmd(argp->sev_fd, SEV_CMD_SNP_LAUNCH_UPDATE,
+                      &data, &argp->error);
+        if (ret) {
+            snp_page_reclaim(pfn);
+            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 kvm_sev_snp_launch_finish params;
+    struct sev_data_snp_launch_finish *data;
+    void *id_block = NULL, *id_auth = NULL;
+    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 finalizing 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);
+
+        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->id_auth_paddr = __sme_pa(id_auth);
+
+        if (params.auth_key_en)
+            data->auth_key_en = 1;
+    }
+
+    data->gctx_paddr = __psp_pa(sev->snp_context);

This is missing the copying of the params.host_data field into the data->host_data field. This is needed so that the host_data shows up in the attestation report.


Yes will fix this.

Thanks,
Ashish

Thanks,
Tom

+    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 sev_mem_enc_ioctl(struct kvm *kvm, void __user *argp)
  {
      struct kvm_sev_cmd sev_cmd;
@@ -2339,6 +2439,9 @@ int sev_mem_enc_ioctl(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;
@@ -2794,11 +2897,27 @@ void sev_free_vcpu(struct kvm_vcpu *vcpu)
      svm = to_svm(vcpu);
+    /*
+     * If its an SNP guest, then VMSA was added in the RMP entry as
+     * a guest owned page. Transition the page to hypervisor state
+     * before releasing it back to the system.
+     * Also the page is removed from the kernel direct map, so flush it
+     * later after it is transitioned back to hypervisor state and
+     * restored in the direct map.
+     */
+    if (sev_snp_guest(vcpu->kvm)) {
+        u64 pfn = __pa(svm->sev_es.vmsa) >> PAGE_SHIFT;
+
+        if (host_rmp_make_shared(pfn, PG_LEVEL_4K, true))
+            goto skip_vmsa_free;
+    }
+
      if (vcpu->arch.guest_state_protected)
          sev_flush_encrypted_page(vcpu, svm->sev_es.vmsa);
      __free_page(virt_to_page(svm->sev_es.vmsa));
+skip_vmsa_free:
      if (svm->sev_es.ghcb_sa_free)
          kvfree(svm->sev_es.ghcb_sa);
  }
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 9b6c95cc62a8..c468adc1f147 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1942,6 +1942,7 @@ enum sev_cmd_id {
      KVM_SEV_SNP_INIT,
      KVM_SEV_SNP_LAUNCH_START,
      KVM_SEV_SNP_LAUNCH_UPDATE,
+    KVM_SEV_SNP_LAUNCH_FINISH,
      KVM_SEV_NR_MAX,
  };
@@ -2076,6 +2077,19 @@ struct kvm_sev_snp_launch_update {
      __u8 vmpl1_perms;
  };
+#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];
+    __u8 pad[6];
+};
+
  #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)



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