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References: <20210402014438.1721086-1-srutherford@google.com>
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From:   Nathan Tempelman <natet@google.com>
Date:   Thu, 8 Apr 2021 15:02:41 -0700
Message-ID: <CAKiEG5pRD4+1dJW=pkpuUKudmPqeTfsVttUG22zo_8FC5_SjfA@mail.gmail.com>
Subject: Re: [PATCH] KVM: SVM: Add support for KVM_SEV_SEND_CANCEL command
To:     Steve Rutherford <srutherford@google.com>
Cc:     kvm <kvm@vger.kernel.org>, linux-kernel@vger.kernel.org,
        Ashish Kalra <Ashish.Kalra@amd.com>,
        Brijesh Singh <brijesh.singh@amd.com>,
        Paolo Bonzini <pbonzini@redhat.com>
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On Thu, Apr 1, 2021 at 6:45 PM Steve Rutherford <srutherford@google.com> wrote:
>
> After completion of SEND_START, but before SEND_FINISH, the source VMM can
> issue the SEND_CANCEL command to stop a migration. This is necessary so
> that a cancelled migration can restart with a new target later.
>
> Signed-off-by: Steve Rutherford <srutherford@google.com>
> ---
>  .../virt/kvm/amd-memory-encryption.rst        |  9 +++++++
>  arch/x86/kvm/svm/sev.c                        | 24 +++++++++++++++++++
>  include/linux/psp-sev.h                       | 10 ++++++++
>  include/uapi/linux/kvm.h                      |  2 ++
>  4 files changed, 45 insertions(+)
>
> diff --git a/Documentation/virt/kvm/amd-memory-encryption.rst b/Documentation/virt/kvm/amd-memory-encryption.rst
> index 469a6308765b1..9e018a3eec03b 100644
> --- a/Documentation/virt/kvm/amd-memory-encryption.rst
> +++ b/Documentation/virt/kvm/amd-memory-encryption.rst
> @@ -284,6 +284,15 @@ Returns: 0 on success, -negative on error
>                  __u32 len;
>          };
>
> +16. KVM_SEV_SEND_CANCEL
> +------------------------
> +
> +After completion of SEND_START, but before SEND_FINISH, the source VMM can issue the
> +SEND_CANCEL command to stop a migration. This is necessary so that a cancelled
> +migration can restart with a new target later.
> +
> +Returns: 0 on success, -negative on error
> +
>  References
>  ==========
>
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index 83e00e5245136..88e72102cb900 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -1110,6 +1110,27 @@ static int sev_get_attestation_report(struct kvm *kvm, struct kvm_sev_cmd *argp)
>         return ret;
>  }
>
> +static int sev_send_cancel(struct kvm *kvm, struct kvm_sev_cmd *argp)
> +{
> +       struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
> +       struct sev_data_send_cancel *data;
> +       int ret;
> +
> +       if (!sev_guest(kvm))
> +               return -ENOTTY;
> +
> +       data = kzalloc(sizeof(*data), GFP_KERNEL);
> +       if (!data)
> +               return -ENOMEM;
> +
> +       data->handle = sev->handle;
> +       ret = sev_issue_cmd(kvm, SEV_CMD_SEND_CANCEL, data, &argp->error);
> +
> +       kfree(data);
> +       return ret;
> +}
> +
> +
>  int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
>  {
>         struct kvm_sev_cmd sev_cmd;
> @@ -1163,6 +1184,9 @@ int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
>         case KVM_SEV_GET_ATTESTATION_REPORT:
>                 r = sev_get_attestation_report(kvm, &sev_cmd);
>                 break;
> +       case KVM_SEV_SEND_CANCEL:
> +               r = sev_send_cancel(kvm, &sev_cmd);
> +               break;
>         default:
>                 r = -EINVAL;
>                 goto out;
> diff --git a/include/linux/psp-sev.h b/include/linux/psp-sev.h
> index b801ead1e2bb5..74f2babffc574 100644
> --- a/include/linux/psp-sev.h
> +++ b/include/linux/psp-sev.h
> @@ -73,6 +73,7 @@ enum sev_cmd {
>         SEV_CMD_SEND_UPDATE_DATA        = 0x041,
>         SEV_CMD_SEND_UPDATE_VMSA        = 0x042,
>         SEV_CMD_SEND_FINISH             = 0x043,
> +       SEV_CMD_SEND_CANCEL             = 0x044,
>
>         /* Guest migration commands (incoming) */
>         SEV_CMD_RECEIVE_START           = 0x050,
> @@ -392,6 +393,15 @@ struct sev_data_send_finish {
>         u32 handle;                             /* In */
>  } __packed;
>
> +/**
> + * struct sev_data_send_cancel - SEND_CANCEL command parameters
> + *
> + * @handle: handle of the VM to process
> + */
> +struct sev_data_send_cancel {
> +       u32 handle;                             /* In */
> +} __packed;
> +
>  /**
>   * struct sev_data_receive_start - RECEIVE_START command parameters
>   *
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index f6afee209620d..707469b6b7072 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -1671,6 +1671,8 @@ enum sev_cmd_id {
>         KVM_SEV_CERT_EXPORT,
>         /* Attestation report */
>         KVM_SEV_GET_ATTESTATION_REPORT,
> +       /* Guest Migration Extension */
> +       KVM_SEV_SEND_CANCEL,
>
>         KVM_SEV_NR_MAX,
>  };
> --
> 2.31.0.208.g409f899ff0-goog
>

Reviewed-by: Nathan Tempelman <natet@google.com>