RE: [PATCH v4 05/23] cxl: Add callback to parse the DSMAS subtables from CDAT

[Dan Williams <dan.j.williams@intel.com>]

Dave Jiang wrote:
> Provide a callback function to the CDAT parser in order to parse the Device
> Scoped Memory Affinity Structure (DSMAS). Each DSMAS structure contains the
> DPA range and its associated attributes in each entry. See the CDAT
> specification for details.
> 
> Coherent Device Attribute Table 1.03 2.1 Device Scoped memory Affinity
> Structure (DSMAS)
> 
> Signed-off-by: Dave Jiang <dave.jiang@intel.com>
> 
> ---
> v3:
> - Add spec section number. (Alison)
> - Remove cast from void *. (Alison)
> - Refactor cxl_port_probe() block. (Alison)
> - Move CDAT parse to cxl_endpoint_port_probe()
> 
> v2:
> - Add DSMAS table size check. (Lukas)
> - Use local DSMAS header for LE handling.
> - Remove dsmas lock. (Jonathan)
> - Fix handle size (Jonathan)
> - Add LE to host conversion for DSMAS address and length.
> - Make dsmas_list local
> ---
>  drivers/cxl/core/cdat.c |   26 ++++++++++++++++++++++++++
>  drivers/cxl/cxl.h       |    1 +
>  drivers/cxl/cxlpci.h    |   18 ++++++++++++++++++
>  drivers/cxl/port.c      |   22 ++++++++++++++++++++++
>  4 files changed, 67 insertions(+)
> 
> diff --git a/drivers/cxl/core/cdat.c b/drivers/cxl/core/cdat.c
> index 210f4499bddb..6f20af83a3ed 100644
> --- a/drivers/cxl/core/cdat.c
> +++ b/drivers/cxl/core/cdat.c
> @@ -98,3 +98,29 @@ int cdat_table_parse_sslbis(struct cdat_header *table,
>  	return cdat_table_parse_entries(CDAT_TYPE_SSLBIS, table, &proc);
>  }
>  EXPORT_SYMBOL_NS_GPL(cdat_table_parse_sslbis, CXL);
> +
> +int cxl_dsmas_parse_entry(struct cdat_entry_header *header, void *arg)
> +{
> +	struct cdat_dsmas *dsmas = (struct cdat_dsmas *)header;
> +	struct list_head *dsmas_list = arg;
> +	struct dsmas_entry *dent;
> +
> +	if (dsmas->hdr.length != sizeof(*dsmas)) {
> +		pr_warn("Malformed DSMAS table length: (%lu:%u)\n",
> +			 (unsigned long)sizeof(*dsmas), dsmas->hdr.length);
> +		return -EINVAL;
> +	}
> +
> +	dent = kzalloc(sizeof(*dent), GFP_KERNEL);
> +	if (!dent)
> +		return -ENOMEM;
> +
> +	dent->handle = dsmas->dsmad_handle;
> +	dent->dpa_range.start = le64_to_cpu(dsmas->dpa_base_address);
> +	dent->dpa_range.end = le64_to_cpu(dsmas->dpa_base_address) +
> +			      le64_to_cpu(dsmas->dpa_length) - 1;
> +	list_add_tail(&dent->list, dsmas_list);
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_NS_GPL(cxl_dsmas_parse_entry, CXL);
> diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
> index 278ab6952332..18ca25c7e527 100644
> --- a/drivers/cxl/cxl.h
> +++ b/drivers/cxl/cxl.h
> @@ -8,6 +8,7 @@
>  #include <linux/bitfield.h>
>  #include <linux/bitops.h>
>  #include <linux/log2.h>
> +#include <linux/list.h>
>  #include <linux/io.h>
>  
>  /**
> diff --git a/drivers/cxl/cxlpci.h b/drivers/cxl/cxlpci.h
> index 45e2f2bf5ef8..9a2468a93d83 100644
> --- a/drivers/cxl/cxlpci.h
> +++ b/drivers/cxl/cxlpci.h
> @@ -104,6 +104,22 @@ struct cdat_subtable_entry {
>  	enum cdat_type type;
>  };
>  
> +struct dsmas_entry {
> +	struct list_head list;
> +	struct range dpa_range;
> +	u8 handle;
> +};
> +
> +/* Sub-table 0: Device Scoped Memory Affinity Structure (DSMAS) */
> +struct cdat_dsmas {
> +	struct cdat_entry_header hdr;
> +	u8 dsmad_handle;
> +	u8 flags;
> +	__u16 reserved;
> +	__le64 dpa_base_address;
> +	__le64 dpa_length;
> +} __packed;
> +
>  int devm_cxl_port_enumerate_dports(struct cxl_port *port);
>  struct cxl_dev_state;
>  int cxl_hdm_decode_init(struct cxl_dev_state *cxlds, struct cxl_hdm *cxlhdm,
> @@ -119,4 +135,6 @@ int cdat_table_parse_##x(struct cdat_header *table, \
>  cdat_table_parse(dsmas);
>  cdat_table_parse(dslbis);
>  cdat_table_parse(sslbis);
> +
> +int cxl_dsmas_parse_entry(struct cdat_entry_header *header, void *arg);
>  #endif /* __CXL_PCI_H__ */
> diff --git a/drivers/cxl/port.c b/drivers/cxl/port.c
> index 615e0ef6b440..3022bdd52439 100644
> --- a/drivers/cxl/port.c
> +++ b/drivers/cxl/port.c
> @@ -57,6 +57,16 @@ static int discover_region(struct device *dev, void *root)
>  	return 0;
>  }
>  
> +static void dsmas_list_destroy(struct list_head *dsmas_list)
> +{
> +	struct dsmas_entry *dentry, *n;
> +
> +	list_for_each_entry_safe(dentry, n, dsmas_list, list) {
> +		list_del(&dentry->list);
> +		kfree(dentry);
> +	}
> +}
> +
>  static int cxl_switch_port_probe(struct cxl_port *port)
>  {
>  	struct cxl_hdm *cxlhdm;
> @@ -125,6 +135,18 @@ static int cxl_endpoint_port_probe(struct cxl_port *port)
>  	device_for_each_child(&port->dev, root, discover_region);
>  	put_device(&root->dev);
>  
> +	if (port->cdat.table) {
> +		LIST_HEAD(dsmas_list);
> +
> +		rc = cdat_table_parse_dsmas(port->cdat.table,
> +					    cxl_dsmas_parse_entry,
> +					    (void *)&dsmas_list);
> +		if (rc < 0)
> +			dev_warn(&port->dev, "Failed to parse DSMAS: %d\n", rc);
> +
> +		dsmas_list_destroy(&dsmas_list);
> +	}
> +

Do these entries need to be cached in a list? For example all the table
walking in drivers/acpi/numa/srat.c injects the data directly into their
final kernel data structure location, it's all self contained in the
parse handler.