Re: [PATCH V12 7/9] cxl/port: Introduce cxl_cdat_valid()

Jonathan Cameron
2022-06-28T14:49:55Z

On Mon, 27 Jun 2022 21:15:25 -0700
ira.weiny@intel.com wrote:

> From: Ira Weiny <ira.weiny@intel.com>
>
> The CDAT data is protected by a checksum and should be the proper
> length.
>
> Introduce cxl_cdat_valid() to validate the data. While at it check and
> store the sequence number.
>
> Signed-off-by: Ira Weiny <ira.weiny@intel.com>
>
Minor ordering comment. With that tidied up
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

> diff --git a/drivers/cxl/core/pci.c b/drivers/cxl/core/pci.c
> index 4bd479ec0253..6d775cc3dca1 100644
> --- a/drivers/cxl/core/pci.c
> +++ b/drivers/cxl/core/pci.c
> @@ -532,6 +532,40 @@ static int cxl_cdat_get_length(struct device *dev,
> return rc;
> }
>
> +static bool cxl_cdat_valid(struct device *dev, struct cxl_cdat *cdat)
> +{
> + u32 *table = cdat->table;
> + u8 *data8 = cdat->table;
> + u32 length, seq;
> + u8 check;
> + int i;
> +
> + length = FIELD_GET(CDAT_HEADER_DW0_LENGTH, table[0]);
> + if ((length < CDAT_HEADER_LENGTH_BYTES) || (length > cdat->length)) {
> + dev_err(dev, "CDAT Invalid length %u (%zu-%zu)\n", length,
> + CDAT_HEADER_LENGTH_BYTES, cdat->length);
> + return false;
> + }
> +
> + for (check = 0, i = 0; i < length; i++)
> + check += data8[i];
> +
> + dev_dbg(dev, "CDAT length %u CS %u\n", length, check);
> + if (check != 0) {
> + dev_err(dev, "CDAT Invalid checksum %u\n", check);
> + return false;
> + }
> +
> + seq = FIELD_GET(CDAT_HEADER_DW3_SEQUENCE, table[3]);
> + /* Store the sequence for now. */
> + if (cdat->seq != seq) {
> + dev_info(dev, "CDAT seq change %x -> %x\n", cdat->seq, seq);
> + cdat->seq = seq;
> + }
> +
> + return true;
> +}
> +
> static int cxl_cdat_read_table(struct device *dev,
> struct pci_doe_mb *cdat_mb,
> struct cxl_cdat *cdat)
> @@ -579,6 +613,8 @@ static int cxl_cdat_read_table(struct device *dev,
>
> } while (entry_handle != CXL_DOE_TABLE_ACCESS_LAST_ENTRY);
>
> + if (!rc && !cxl_cdat_valid(dev, cdat))
> + return -EIO;

I'd prefer those handled separately as flow is more readable if error
handling always out of line.

if (rc)
return rc;

if (!cxl_cdata_valid)
return -EIO;

return 0;

> return rc;
> }
>