Re: [PATCH 06/18] cxl: Add callback to parse the DSMAS subtables from CDAT

[Jonathan Cameron <Jonathan.Cameron@Huawei.com>]

On Mon, 06 Feb 2023 13:50:15 -0700
Dave Jiang <dave.jiang@intel.com> 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.
> 
> Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Hi Dave,

A few minor questions / comments inline,

Jonathan

> ---
>  drivers/cxl/core/cdat.c |   25 +++++++++++++++++++++++++
>  drivers/cxl/core/port.c |    2 ++
>  drivers/cxl/cxl.h       |   11 +++++++++++
>  drivers/cxl/port.c      |    8 ++++++++
>  4 files changed, 46 insertions(+)
> 
> diff --git a/drivers/cxl/core/cdat.c b/drivers/cxl/core/cdat.c
> index be09c8a690f5..f9a64a0f1ee4 100644
> --- a/drivers/cxl/core/cdat.c
> +++ b/drivers/cxl/core/cdat.c
> @@ -96,3 +96,28 @@ int cdat_table_parse_dslbis(void *table, cdat_tbl_entry_handler handler, void *a
>  	return cdat_table_parse_entries(ACPI_CDAT_TYPE_DSLBIS, header, &proc, 0);
>  }
>  EXPORT_SYMBOL_NS_GPL(cdat_table_parse_dslbis, CXL);
> +
> +int cxl_dsmas_parse_entry(struct acpi_cdat_header *header, void *arg)
> +{
> +	struct cxl_port *port = (struct cxl_port *)arg;
> +	struct dsmas_entry *dent;
> +	struct acpi_cdat_dsmas *dsmas;
> +
> +	if (header->type != ACPI_CDAT_TYPE_DSMAS)
> +		return -EINVAL;
> +
> +	dent = devm_kzalloc(&port->dev, sizeof(*dent), GFP_KERNEL);
> +	if (!dent)
> +		return -ENOMEM;
> +
> +	dsmas = (struct acpi_cdat_dsmas *)((unsigned long)header + sizeof(*header));

I'd prefer header + 1


> +	dent->handle = dsmas->dsmad_handle;
> +	dent->dpa_range.start = dsmas->dpa_base_address;
> +	dent->dpa_range.end = dsmas->dpa_base_address + dsmas->dpa_length - 1;
> +
> +	mutex_lock(&port->cdat.dsmas_lock);
> +	list_add_tail(&dent->list, &port->cdat.dsmas_list);
> +	mutex_unlock(&port->cdat.dsmas_lock);
> +	return 0;
> +}
> +EXPORT_SYMBOL_NS_GPL(cxl_dsmas_parse_entry, CXL);
> diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
> index fe78daf7e7c8..2b27319cfd42 100644
> --- a/drivers/cxl/core/port.c
> +++ b/drivers/cxl/core/port.c
> @@ -660,6 +660,8 @@ static struct cxl_port *cxl_port_alloc(struct device *uport,
>  	device_set_pm_not_required(dev);
>  	dev->bus = &cxl_bus_type;
>  	dev->type = &cxl_port_type;
> +	INIT_LIST_HEAD(&port->cdat.dsmas_list);
> +	mutex_init(&port->cdat.dsmas_lock);
>  
>  	return port;
>  
> diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
> index 839a121c1997..1e5e69f08480 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>
>  #include <linux/acpi.h>
>  
> @@ -520,6 +521,8 @@ struct cxl_port {
>  	struct cxl_cdat {
>  		void *table;
>  		size_t length;
> +		struct list_head dsmas_list;
> +		struct mutex dsmas_lock; /* lock for dsmas_list */

I'm curious, what might race with the dsmas_list changing and hence what is lock for?

>  	} cdat;
>  	bool cdat_available;
>  };
> @@ -698,6 +701,12 @@ static inline struct cxl_pmem_region *to_cxl_pmem_region(struct device *dev)
>  }
>  #endif
>  
> +struct dsmas_entry {
> +	struct list_head list;
> +	struct range dpa_range;
> +	u16 handle;

handle is 1 byte in the spec. Why larger here?

> +};
> +
>  typedef int (*cdat_tbl_entry_handler)(struct acpi_cdat_header *header, void *arg);
>  
>  u8 cdat_table_checksum(u8 *buffer, u32 length);
> @@ -706,6 +715,8 @@ int cdat_table_parse_dsmas(void *table, cdat_tbl_entry_handler handler,
>  int cdat_table_parse_dslbis(void *table, cdat_tbl_entry_handler handler,
>  			    void *arg);
>  
> +int cxl_dsmas_parse_entry(struct acpi_cdat_header *header, void *arg);
> +
>  /*
>   * Unit test builds overrides this to __weak, find the 'strong' version
>   * of these symbols in tools/testing/cxl/.
> diff --git a/drivers/cxl/port.c b/drivers/cxl/port.c
> index 5453771bf330..b1da73e99bab 100644
> --- a/drivers/cxl/port.c
> +++ b/drivers/cxl/port.c
> @@ -61,6 +61,14 @@ static int cxl_port_probe(struct device *dev)
>  		if (rc)
>  			return rc;
>  
> +		if (port->cdat.table) {
> +			rc = cdat_table_parse_dsmas(port->cdat.table,
> +						    cxl_dsmas_parse_entry,
> +						    (void *)port);
> +			if (rc < 0)
> +				dev_dbg(dev, "Failed to parse DSMAS: %d\n", rc);
> +		}
> +
>  		rc = cxl_hdm_decode_init(cxlds, cxlhdm);
>  		if (rc)
>  			return rc;
> 
>