Re: [PATCH v12 04/13] KVM: SVM: Add support for KVM_SEV_RECEIVE_START command

[Steve Rutherford <srutherford@google.com>]

On Mon, Apr 12, 2021 at 12:44 PM Ashish Kalra <Ashish.Kalra@amd.com> wrote:
>
> From: Brijesh Singh <brijesh.singh@amd.com>
>
> The command is used to create the encryption context for an incoming
> SEV guest. The encryption context can be later used by the hypervisor
> to import the incoming data into the SEV guest memory space.
>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Joerg Roedel <joro@8bytes.org>
> Cc: Borislav Petkov <bp@suse.de>
> Cc: Tom Lendacky <thomas.lendacky@amd.com>
> Cc: x86@kernel.org
> Cc: kvm@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
> Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
> ---
>  .../virt/kvm/amd-memory-encryption.rst        | 29 +++++++
>  arch/x86/kvm/svm/sev.c                        | 81 +++++++++++++++++++
>  include/uapi/linux/kvm.h                      |  9 +++
>  3 files changed, 119 insertions(+)
>
> diff --git a/Documentation/virt/kvm/amd-memory-encryption.rst b/Documentation/virt/kvm/amd-memory-encryption.rst
> index 26c4e6c83f62..c86c1ded8dd8 100644
> --- a/Documentation/virt/kvm/amd-memory-encryption.rst
> +++ b/Documentation/virt/kvm/amd-memory-encryption.rst
> @@ -343,6 +343,35 @@ issued by the hypervisor to delete the encryption context.
>
>  Returns: 0 on success, -negative on error
>
> +13. KVM_SEV_RECEIVE_START
> +------------------------
> +
> +The KVM_SEV_RECEIVE_START command is used for creating the memory encryption
> +context for an incoming SEV guest. To create the encryption context, the user must
> +provide a guest policy, the platform public Diffie-Hellman (PDH) key and session
> +information.
> +
> +Parameters: struct  kvm_sev_receive_start (in/out)
> +
> +Returns: 0 on success, -negative on error
> +
> +::
> +
> +        struct kvm_sev_receive_start {
> +                __u32 handle;           /* if zero then firmware creates a new handle */
> +                __u32 policy;           /* guest's policy */
> +
> +                __u64 pdh_uaddr;        /* userspace address pointing to the PDH key */
> +                __u32 pdh_len;
> +
> +                __u64 session_uaddr;    /* userspace address which points to the guest session information */
> +                __u32 session_len;
> +        };
> +
> +On success, the 'handle' field contains a new handle and on error, a negative value.
> +
> +For more details, see SEV spec Section 6.12.
> +
>  References
>  ==========
>
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index 92325d9527ce..e530c2b34b5e 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -1370,6 +1370,84 @@ static int sev_send_finish(struct kvm *kvm, struct kvm_sev_cmd *argp)
>         return ret;
>  }
>
> +static int sev_receive_start(struct kvm *kvm, struct kvm_sev_cmd *argp)
> +{
> +       struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
> +       struct sev_data_receive_start *start;
> +       struct kvm_sev_receive_start params;
> +       int *error = &argp->error;
> +       void *session_data;
> +       void *pdh_data;
> +       int ret;
> +
> +       if (!sev_guest(kvm))
> +               return -ENOTTY;
> +
> +       /* Get parameter from the userspace */
> +       if (copy_from_user(&params, (void __user *)(uintptr_t)argp->data,
> +                       sizeof(struct kvm_sev_receive_start)))
> +               return -EFAULT;
> +
> +       /* some sanity checks */
> +       if (!params.pdh_uaddr || !params.pdh_len ||
> +           !params.session_uaddr || !params.session_len)
> +               return -EINVAL;
> +
> +       pdh_data = psp_copy_user_blob(params.pdh_uaddr, params.pdh_len);
> +       if (IS_ERR(pdh_data))
> +               return PTR_ERR(pdh_data);
> +
> +       session_data = psp_copy_user_blob(params.session_uaddr,
> +                       params.session_len);
> +       if (IS_ERR(session_data)) {
> +               ret = PTR_ERR(session_data);
> +               goto e_free_pdh;
> +       }
> +
> +       ret = -ENOMEM;
> +       start = kzalloc(sizeof(*start), GFP_KERNEL);
> +       if (!start)
> +               goto e_free_session;
> +
> +       start->handle = params.handle;
> +       start->policy = params.policy;
> +       start->pdh_cert_address = __psp_pa(pdh_data);
> +       start->pdh_cert_len = params.pdh_len;
> +       start->session_address = __psp_pa(session_data);
> +       start->session_len = params.session_len;
> +
> +       /* create memory encryption context */
> +       ret = __sev_issue_cmd(argp->sev_fd, SEV_CMD_RECEIVE_START, start,
> +                               error);
> +       if (ret)
> +               goto e_free;
> +
> +       /* Bind ASID to this guest */
> +       ret = sev_bind_asid(kvm, start->handle, error);
> +       if (ret)
> +               goto e_free;
> +
> +       params.handle = start->handle;
> +       if (copy_to_user((void __user *)(uintptr_t)argp->data,
> +                        &params, sizeof(struct kvm_sev_receive_start))) {
> +               ret = -EFAULT;
> +               sev_unbind_asid(kvm, start->handle);
> +               goto e_free;
> +       }
> +
> +       sev->handle = start->handle;
> +       sev->fd = argp->sev_fd;
> +
> +e_free:
> +       kfree(start);
> +e_free_session:
> +       kfree(session_data);
> +e_free_pdh:
> +       kfree(pdh_data);
> +
> +       return ret;
> +}
> +
>  int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
>  {
>         struct kvm_sev_cmd sev_cmd;
> @@ -1432,6 +1510,9 @@ int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
>         case KVM_SEV_SEND_FINISH:
>                 r = sev_send_finish(kvm, &sev_cmd);
>                 break;
> +       case KVM_SEV_RECEIVE_START:
> +               r = sev_receive_start(kvm, &sev_cmd);
> +               break;
>         default:
>                 r = -EINVAL;
>                 goto out;
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index d45af34c31be..29c25e641a0c 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -1750,6 +1750,15 @@ struct kvm_sev_send_update_data {
>         __u32 trans_len;
>  };
>
> +struct kvm_sev_receive_start {
> +       __u32 handle;
> +       __u32 policy;
> +       __u64 pdh_uaddr;
> +       __u32 pdh_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)
> --
> 2.17.1
>
Reviewed-by: Steve Rutherford <srutherford@google.com>