Re: [PATCH v9 02/19] cxl/mem: Read dynamic capacity configuration from the device

[Fan Ni <nifan.cxl@gmail.com>]

On Sun, Apr 13, 2025 at 05:52:10PM -0500, Ira Weiny wrote:
> Devices which optionally support Dynamic Capacity (DC) are configured
> via mailbox commands.  CXL 3.2 section 9.13.3 requires the host to issue
> the Get DC Configuration command in order to properly configure DCDs.
> Without the Get DC Configuration command DCD can't be supported.
> 
> Implement the DC mailbox commands as specified in CXL 3.2 section
> 8.2.10.9.9 (opcodes 48XXh) to read and store the DCD configuration
> information.  Disable DCD if an invalid configuration is found.
> 
> Linux has no support for more than one dynamic capacity partition.  Read
> and validate all the partitions but configure only the first partition
> as 'dynamic ram A'.  Additional partitions can be added in the future if
> such a device ever materializes.  Additionally is it anticipated that no
> skips will be present from the end of the pmem partition.  Check for an
> disallow this configuration as well.
> 
> Linux has no use for the trailing fields of the Get Dynamic Capacity
> Configuration Output Payload (Total number of supported extents, number
> of available extents, total number of supported tags, and number of
> available tags).  Avoid defining those fields to use the more useful
> dynamic C array.
> 
> Based on an original patch by Navneet Singh.
> 
> Signed-off-by: Ira Weiny <ira.weiny@intel.com>
> 
> ---
> Changes:
> [iweiny: rebase]
> [iweiny: Update spec references to 3.2]
> [djbw: Limit to 1 partition]
> [djbw: Avoid inter-partition skipping]
> [djbw: s/region/partition/]
> [djbw: remove cxl_dc_region[partition]_info->name]
> [iweiny: adjust to lack of dcd_cmds in mds]
> [iweiny: remove extra 'region' from names]
> [iweiny: remove unused CXL_DYNAMIC_CAPACITY_SANITIZE_ON_RELEASE_FLAG]
> ---
>  drivers/cxl/core/hdm.c  |   2 +
>  drivers/cxl/core/mbox.c | 179 ++++++++++++++++++++++++++++++++++++++++++++++++
>  drivers/cxl/cxl.h       |   1 +
>  drivers/cxl/cxlmem.h    |  54 ++++++++++++++-
>  drivers/cxl/pci.c       |   3 +
>  5 files changed, 238 insertions(+), 1 deletion(-)
...
>  /* Set Timestamp CXL 3.0 Spec 8.2.9.4.2 */
>  struct cxl_mbox_set_timestamp_in {
>  	__le64 timestamp;
> @@ -845,9 +871,24 @@ enum {
>  int cxl_internal_send_cmd(struct cxl_mailbox *cxl_mbox,
>  			  struct cxl_mbox_cmd *cmd);
>  int cxl_dev_state_identify(struct cxl_memdev_state *mds);
> +
> +struct cxl_mem_dev_info {
> +	u64 total_bytes;
> +	u64 volatile_bytes;
> +	u64 persistent_bytes;
> +};

Defined, but never used.

Fan

> +
> +struct cxl_dc_partition_info {
> +	size_t start;
> +	size_t size;
> +};
> +
> +int cxl_dev_dc_identify(struct cxl_mailbox *mbox,
> +			struct cxl_dc_partition_info *dc_info);
>  int cxl_await_media_ready(struct cxl_dev_state *cxlds);
>  int cxl_enumerate_cmds(struct cxl_memdev_state *mds);
>  int cxl_mem_dpa_fetch(struct cxl_memdev_state *mds, struct cxl_dpa_info *info);
> +void cxl_configure_dcd(struct cxl_memdev_state *mds, struct cxl_dpa_info *info);
>  struct cxl_memdev_state *cxl_memdev_state_create(struct device *dev);
>  void set_exclusive_cxl_commands(struct cxl_memdev_state *mds,
>  				unsigned long *cmds);
> @@ -860,6 +901,17 @@ void cxl_event_trace_record(const struct cxl_memdev *cxlmd,
>  			    const uuid_t *uuid, union cxl_event *evt);
>  int cxl_get_dirty_count(struct cxl_memdev_state *mds, u32 *count);
>  int cxl_arm_dirty_shutdown(struct cxl_memdev_state *mds);
> +
> +static inline bool cxl_dcd_supported(struct cxl_memdev_state *mds)
> +{
> +	return mds->dcd_supported;
> +}
> +
> +static inline void cxl_disable_dcd(struct cxl_memdev_state *mds)
> +{
> +	mds->dcd_supported = false;
> +}
> +
>  int cxl_set_timestamp(struct cxl_memdev_state *mds);
>  int cxl_poison_state_init(struct cxl_memdev_state *mds);
>  int cxl_mem_get_poison(struct cxl_memdev *cxlmd, u64 offset, u64 len,
> diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
> index 7b14a154463c..bc40cf6e2fe9 100644
> --- a/drivers/cxl/pci.c
> +++ b/drivers/cxl/pci.c
> @@ -998,6 +998,9 @@ static int cxl_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
>  	if (rc)
>  		return rc;
>  
> +	if (cxl_dcd_supported(mds))
> +		cxl_configure_dcd(mds, &range_info);
> +
>  	rc = cxl_dpa_setup(cxlds, &range_info);
>  	if (rc)
>  		return rc;
> 
> -- 
> 2.49.0
> 

-- 
Fan Ni