Re: [PATCH] powerpc/nvdimm: Add support for multibyte read/write for metadata

[Oliver <oohall@gmail.com>]

On Sun, Jun 2, 2019 at 2:44 PM Aneesh Kumar K.V
<aneesh.kumar@linux.ibm.com> wrote:
>
> SCM_READ/WRITE_MEATADATA hcall supports multibyte read/write. This patch
> updates the metadata read/write to use 1, 2, 4 or 8 byte read/write as
> mentioned in PAPR document.
>
> READ/WRITE_METADATA hcall supports the 1, 2, 4, or 8 bytes read/write.
> For other values hcall results H_P3.

You should probably fold the second paragraph here into the first.

> Hypervisor stores the metadata contents in big-endian format and in-order
> to enable read/write in different granularity, we need to switch the contents
> to big-endian before calling HCALL.
>
> Based on an patch from Oliver O'Halloran <oohall@gmail.com>
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
> ---
>  arch/powerpc/platforms/pseries/papr_scm.c | 104 +++++++++++++++++-----
>  1 file changed, 82 insertions(+), 22 deletions(-)
>
> diff --git a/arch/powerpc/platforms/pseries/papr_scm.c b/arch/powerpc/platforms/pseries/papr_scm.c
> index 0176ce66673f..e33cebb8ee6c 100644
> --- a/arch/powerpc/platforms/pseries/papr_scm.c
> +++ b/arch/powerpc/platforms/pseries/papr_scm.c
> @@ -97,42 +97,102 @@ static int drc_pmem_unbind(struct papr_scm_priv *p)
>  }
>
>  static int papr_scm_meta_get(struct papr_scm_priv *p,
> -                       struct nd_cmd_get_config_data_hdr *hdr)
> +                            struct nd_cmd_get_config_data_hdr *hdr)
>  {
>         unsigned long data[PLPAR_HCALL_BUFSIZE];
> +       unsigned long offset, data_offset;
> +       int len, read;
>         int64_t ret;
>
> -       if (hdr->in_offset >= p->metadata_size || hdr->in_length != 1)
> +       if ((hdr->in_offset + hdr->in_length) >= p->metadata_size)
>                 return -EINVAL;
>
> -       ret = plpar_hcall(H_SCM_READ_METADATA, data, p->drc_index,
> -                       hdr->in_offset, 1);
> -
> -       if (ret == H_PARAMETER) /* bad DRC index */
> -               return -ENODEV;
> -       if (ret)
> -               return -EINVAL; /* other invalid parameter */
> -
> -       hdr->out_buf[0] = data[0] & 0xff;
> -
> +       for (len = hdr->in_length; len; len -= read) {
> +
> +               data_offset = hdr->in_length - len;
> +               offset = hdr->in_offset + data_offset;
> +
> +               if (len >= 8)
> +                       read = 8;
> +               else if (len >= 4)
> +                       read = 4;
> +               else if ( len >= 2)
> +                       read = 2;
> +               else
> +                       read = 1;
> +
> +               ret = plpar_hcall(H_SCM_READ_METADATA, data, p->drc_index,
> +                                 offset, read);
> +
> +               if (ret == H_PARAMETER) /* bad DRC index */
> +                       return -ENODEV;
> +               if (ret)
> +                       return -EINVAL; /* other invalid parameter */
> +
> +               switch (read) {
> +               case 8:
> +                       *(uint64_t *)(hdr->out_buf + data_offset) = be64_to_cpu(data[0]);
> +                       break;
> +               case 4:
> +                       *(uint32_t *)(hdr->out_buf + data_offset) = be32_to_cpu(data[0] & 0xffffffff);
> +                       break;
> +
> +               case 2:
> +                       *(uint16_t *)(hdr->out_buf + data_offset) = be16_to_cpu(data[0] & 0xffff);
> +                       break;
> +
> +               case 1:
> +                       *(uint32_t *)(hdr->out_buf + data_offset) = (data[0] & 0xff);
> +                       break;
> +               }
> +       }
>         return 0;
>  }
>
>  static int papr_scm_meta_set(struct papr_scm_priv *p,
> -                       struct nd_cmd_set_config_hdr *hdr)
> +                            struct nd_cmd_set_config_hdr *hdr)
>  {
> +       unsigned long offset, data_offset;
> +       int len, wrote;
> +       unsigned long data;
> +       __be64 data_be;
>         int64_t ret;
>
> -       if (hdr->in_offset >= p->metadata_size || hdr->in_length != 1)
> +       if ((hdr->in_offset + hdr->in_length) >= p->metadata_size)
>                 return -EINVAL;
>
> -       ret = plpar_hcall_norets(H_SCM_WRITE_METADATA,
> -                       p->drc_index, hdr->in_offset, hdr->in_buf[0], 1);
> -
> -       if (ret == H_PARAMETER) /* bad DRC index */
> -               return -ENODEV;
> -       if (ret)
> -               return -EINVAL; /* other invalid parameter */
> +       for (len = hdr->in_length; len; len -= wrote) {
> +
> +               data_offset = hdr->in_length - len;
> +               offset = hdr->in_offset + data_offset;
> +
> +               if (len >= 8) {
> +                       data = *(uint64_t *)(hdr->in_buf + data_offset);
> +                       data_be = cpu_to_be64(data);
> +                       wrote = 8;
> +               } else if (len >= 4) {
> +                       data = *(uint32_t *)(hdr->in_buf + data_offset);
> +                       data &= 0xffffffff;
> +                       data_be = cpu_to_be32(data);
> +                       wrote = 4;
> +               } else if (len >= 2) {
> +                       data = *(uint16_t *)(hdr->in_buf + data_offset);
> +                       data &= 0xffff;
> +                       data_be = cpu_to_be16(data);
> +                       wrote = 2;
> +               } else {
> +                       data_be = *(uint8_t *)(hdr->in_buf + data_offset);
> +                       data_be &= 0xff;
> +                       wrote = 1;
> +               }
> +
> +               ret = plpar_hcall_norets(H_SCM_WRITE_METADATA, p->drc_index,
> +                                        offset, data_be, wrote);
> +               if (ret == H_PARAMETER) /* bad DRC index */
> +                       return -ENODEV;
> +               if (ret)
> +                       return -EINVAL; /* other invalid parameter */
> +       }
>
>         return 0;
>  }
> @@ -154,7 +214,7 @@ int papr_scm_ndctl(struct nvdimm_bus_descriptor *nd_desc, struct nvdimm *nvdimm,
>                 get_size_hdr = buf;
>
>                 get_size_hdr->status = 0;
> -               get_size_hdr->max_xfer = 1;
> +               get_size_hdr->max_xfer = 8;
>                 get_size_hdr->config_size = p->metadata_size;
>                 *cmd_rc = 0;
>                 break;
> --
> 2.21.0

I assume you got the qemu bits sorted out with Shiva? Looks good otherwise.

Reviewed-by: Oliver O'Halloran <oohall@gmail.com>