Re: [PATCH Part2 v6 28/49] KVM: SVM: Add KVM_SEV_SNP_LAUNCH_FINISH command

Jarkko Sakkinen
2022-08-02T13:28:37Z

On Mon, Jun 20, 2022 at 11:08:38PM +0000, Ashish Kalra wrote:
> From: Brijesh Singh <brijesh.singh@amd.com>
>
> 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.

Nit: for completeness sake it would nice to fully conclude whether
LAUNCH_UPDATE is usable after LAUNCH_FINISH in this paragraph.

>
> 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@amd.com>
> Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
> ---
> .../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 62abd5c1f72b..750162cff87b 100644
> --- a/Documentation/virt/kvm/x86/amd-memory-encryption.rst
> +++ b/Documentation/virt/kvm/x86/amd-memory-encryption.rst
> @@ -514,6 +514,28 @@ 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.

Some remark about LAUNCH_UPDATE post-LAUNCH_FINISH would be nice.

> +
> +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];
> + };
> +
> +
> +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 a9461d352eda..a5b90469683f 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -2095,6 +2095,106 @@ 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(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 sev_data_snp_launch_finish *data;
> + void *id_block = NULL, *id_auth = NULL;
> + struct kvm_sev_snp_launch_finish params;

Nit: "params" should be the 2nd declaration (reverse
christmas tree order).

> + 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 sev_mem_enc_ioctl(struct kvm *kvm, void __user *argp)
> {
> struct kvm_sev_cmd sev_cmd;
> @@ -2191,6 +2291,9 @@ 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;
> @@ -2696,11 +2799,27 @@ 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, false))
> + 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 9b36b07414ea..5a4662716b6a 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -1814,6 +1814,7 @@ 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,
> };
> @@ -1948,6 +1949,19 @@ 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)
> --
> 2.25.1
>

BR, Jarkko