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From:   Peter Gonda <pgonda@google.com>
Date:   Tue, 21 Jun 2022 15:43:13 -0600
Message-ID: <CAMkAt6qL_p8Fp=ED5hER665GHzQn=nwZQhFg4MwHt7QanS4wVw@mail.gmail.com>
Subject: Re: [PATCH Part2 v6 13/49] crypto:ccp: Provide APIs to issue SEV-SNP commands
To:     Ashish Kalra <Ashish.Kalra@amd.com>
Cc:     "the arch/x86 maintainers" <x86@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
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(

On Mon, Jun 20, 2022 at 5:05 PM Ashish Kalra <Ashish.Kalra@amd.com> wrote:
>
> From: Brijesh Singh <brijesh.singh@amd.com>
>
> Provide the APIs for the hypervisor to manage an SEV-SNP guest. The
> commands for SEV-SNP is defined in the SEV-SNP firmware specification.
>
> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
> ---
>  drivers/crypto/ccp/sev-dev.c | 24 ++++++++++++
>  include/linux/psp-sev.h      | 73 ++++++++++++++++++++++++++++++++++++
>  2 files changed, 97 insertions(+)
>
> diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
> index f1173221d0b9..35d76333e120 100644
> --- a/drivers/crypto/ccp/sev-dev.c
> +++ b/drivers/crypto/ccp/sev-dev.c
> @@ -1205,6 +1205,30 @@ int sev_guest_df_flush(int *error)
>  }
>  EXPORT_SYMBOL_GPL(sev_guest_df_flush);
>
> +int snp_guest_decommission(struct sev_data_snp_decommission *data, int *error)
> +{
> +       return sev_do_cmd(SEV_CMD_SNP_DECOMMISSION, data, error);
> +}
> +EXPORT_SYMBOL_GPL(snp_guest_decommission);
> +
> +int snp_guest_df_flush(int *error)
> +{
> +       return sev_do_cmd(SEV_CMD_SNP_DF_FLUSH, NULL, error);
> +}
> +EXPORT_SYMBOL_GPL(snp_guest_df_flush);

Why not instead change sev_guest_df_flush() to be SNP aware? That way
callers get the right behavior without having to know if SNP is
enabled or not.

int sev_guest_df_flush(int *error)
{
  if (!psp_master || !psp_master->sev_data)
   return -EINVAL;

  if (psp_master->sev_data->snp_inited)
    return sev_do_cmd(SEV_CMD_SNP_DF_FLUSH, NULL, error);

  return sev_do_cmd(SEV_CMD_DF_FLUSH, NULL, error);
}

> +int snp_guest_page_reclaim(struct sev_data_snp_page_reclaim *data, int *error)
> +{
> +       return sev_do_cmd(SEV_CMD_SNP_PAGE_RECLAIM, data, error);
> +}
> +EXPORT_SYMBOL_GPL(snp_guest_page_reclaim);
> +
> +int snp_guest_dbg_decrypt(struct sev_data_snp_dbg *data, int *error)
> +{
> +       return sev_do_cmd(SEV_CMD_SNP_DBG_DECRYPT, data, error);
> +}
> +EXPORT_SYMBOL_GPL(snp_guest_dbg_decrypt);
> +
>  static void sev_exit(struct kref *ref)
>  {
>         misc_deregister(&misc_dev->misc);
> diff --git a/include/linux/psp-sev.h b/include/linux/psp-sev.h
> index ef4d42e8c96e..9f921d221b75 100644
> --- a/include/linux/psp-sev.h
> +++ b/include/linux/psp-sev.h
> @@ -881,6 +881,64 @@ int sev_guest_df_flush(int *error);
>   */
>  int sev_guest_decommission(struct sev_data_decommission *data, int *error);
>
> +/**
> + * snp_guest_df_flush - perform SNP DF_FLUSH command
> + *
> + * @sev_ret: sev command return code
> + *
> + * Returns:
> + * 0 if the sev successfully processed the command
> + * -%ENODEV    if the sev device is not available
> + * -%ENOTSUPP  if the sev does not support SEV
> + * -%ETIMEDOUT if the sev command timed out
> + * -%EIO       if the sev returned a non-zero return code
> + */
> +int snp_guest_df_flush(int *error);
> +
> +/**
> + * snp_guest_decommission - perform SNP_DECOMMISSION command
> + *
> + * @decommission: sev_data_decommission structure to be processed
> + * @sev_ret: sev command return code
> + *
> + * Returns:
> + * 0 if the sev successfully processed the command
> + * -%ENODEV    if the sev device is not available
> + * -%ENOTSUPP  if the sev does not support SEV
> + * -%ETIMEDOUT if the sev command timed out
> + * -%EIO       if the sev returned a non-zero return code
> + */
> +int snp_guest_decommission(struct sev_data_snp_decommission *data, int *error);
> +
> +/**
> + * snp_guest_page_reclaim - perform SNP_PAGE_RECLAIM command
> + *
> + * @decommission: sev_snp_page_reclaim structure to be processed
> + * @sev_ret: sev command return code
> + *
> + * Returns:
> + * 0 if the sev successfully processed the command
> + * -%ENODEV    if the sev device is not available
> + * -%ENOTSUPP  if the sev does not support SEV
> + * -%ETIMEDOUT if the sev command timed out
> + * -%EIO       if the sev returned a non-zero return code
> + */
> +int snp_guest_page_reclaim(struct sev_data_snp_page_reclaim *data, int *error);
> +
> +/**
> + * snp_guest_dbg_decrypt - perform SEV SNP_DBG_DECRYPT command
> + *
> + * @sev_ret: sev command return code
> + *
> + * Returns:
> + * 0 if the sev successfully processed the command
> + * -%ENODEV    if the sev device is not available
> + * -%ENOTSUPP  if the sev does not support SEV
> + * -%ETIMEDOUT if the sev command timed out
> + * -%EIO       if the sev returned a non-zero return code
> + */
> +int snp_guest_dbg_decrypt(struct sev_data_snp_dbg *data, int *error);
> +
>  void *psp_copy_user_blob(u64 uaddr, u32 len);
>
>  #else  /* !CONFIG_CRYPTO_DEV_SP_PSP */
> @@ -908,6 +966,21 @@ sev_issue_cmd_external_user(struct file *filep, unsigned int id, void *data, int
>
>  static inline void *psp_copy_user_blob(u64 __user uaddr, u32 len) { return ERR_PTR(-EINVAL); }
>
> +static inline int
> +snp_guest_decommission(struct sev_data_snp_decommission *data, int *error) { return -ENODEV; }
> +
> +static inline int snp_guest_df_flush(int *error) { return -ENODEV; }
> +
> +static inline int snp_guest_page_reclaim(struct sev_data_snp_page_reclaim *data, int *error)
> +{
> +       return -ENODEV;
> +}
> +
> +static inline int snp_guest_dbg_decrypt(struct sev_data_snp_dbg *data, int *error)
> +{
> +       return -ENODEV;
> +}
> +
>  #endif /* CONFIG_CRYPTO_DEV_SP_PSP */
>
>  #endif /* __PSP_SEV_H__ */
> --
> 2.25.1
>