From: Navneet Singh <navneet.singh@intel.com>

Devices which optionally support Dynamic Capacity (DC) are configured
via mailbox commands.  CXL 3.1 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 3.1 section
8.2.9.9.9 (opcodes 48XXh) to read and store the DCD configuration
information.  Disable DCD if DCD is not supported.  Leverage the Get DC
Configuration command supported bit to indicate if DCD support.

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.

Cc: "Li, Ming" <ming4.li@intel.com>
Signed-off-by: Navneet Singh <navneet.singh@intel.com>
Co-developed-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>

---
Changes:
[iweiny: Adjust for mailbox split]
[djiang: remove setting region names to '<nil>']
[fan: Clean up dev_{err,dbg}]
---
 drivers/cxl/core/mbox.c | 166 +++++++++++++++++++++++++++++++++++++++++++++++-
 drivers/cxl/cxlmem.h    |  64 ++++++++++++++++++-
 drivers/cxl/pci.c       |   4 ++
 3 files changed, 232 insertions(+), 2 deletions(-)

diff --git a/drivers/cxl/core/mbox.c b/drivers/cxl/core/mbox.c
index 8bd5bf1a746d..4b51ddd1ff94 100644
--- a/drivers/cxl/core/mbox.c
+++ b/drivers/cxl/core/mbox.c
@@ -1168,7 +1168,7 @@ int cxl_dev_state_identify(struct cxl_memdev_state *mds)
 	if (rc < 0)
 		return rc;
 
-	mds->total_bytes =
+	mds->static_bytes =
 		le64_to_cpu(id.total_capacity) * CXL_CAPACITY_MULTIPLIER;
 	mds->volatile_only_bytes =
 		le64_to_cpu(id.volatile_capacity) * CXL_CAPACITY_MULTIPLIER;
@@ -1274,6 +1274,154 @@ int cxl_mem_sanitize(struct cxl_memdev *cxlmd, u16 cmd)
 	return rc;
 }
 
+static int cxl_dc_save_region_info(struct cxl_memdev_state *mds, u8 index,
+				   struct cxl_dc_region_config *region_config)
+{
+	struct cxl_dc_region_info *dcr = &mds->dc_region[index];
+	struct device *dev = mds->cxlds.dev;
+
+	dcr->base = le64_to_cpu(region_config->region_base);
+	dcr->decode_len = le64_to_cpu(region_config->region_decode_length);
+	dcr->decode_len *= CXL_CAPACITY_MULTIPLIER;
+	dcr->len = le64_to_cpu(region_config->region_length);
+	dcr->blk_size = le64_to_cpu(region_config->region_block_size);
+	dcr->dsmad_handle = le32_to_cpu(region_config->region_dsmad_handle);
+	dcr->flags = region_config->flags;
+	snprintf(dcr->name, CXL_DC_REGION_STRLEN, "dc%d", index);
+
+	/* Check regions are in increasing DPA order */
+	if (index > 0) {
+		struct cxl_dc_region_info *prev_dcr = &mds->dc_region[index - 1];
+
+		if ((prev_dcr->base + prev_dcr->decode_len) > dcr->base) {
+			dev_err(dev,
+				"DPA ordering violation for DC region %d and %d\n",
+				index - 1, index);
+			return -EINVAL;
+		}
+	}
+
+	if (!IS_ALIGNED(dcr->base, SZ_256M) ||
+	    !IS_ALIGNED(dcr->base, dcr->blk_size)) {
+		dev_err(dev, "DC region %d invalid base %#llx blk size %#llx\n",
+			index, dcr->base, dcr->blk_size);
+		return -EINVAL;
+	}
+
+	if (dcr->decode_len == 0 || dcr->len == 0 || dcr->decode_len < dcr->len ||
+	    !IS_ALIGNED(dcr->len, dcr->blk_size)) {
+		dev_err(dev, "DC region %d invalid length; decode %#llx len %#llx blk size %#llx\n",
+			index, dcr->decode_len, dcr->len, dcr->blk_size);
+		return -EINVAL;
+	}
+
+	if (dcr->blk_size == 0 || dcr->blk_size % CXL_DCD_BLOCK_LINE_SIZE ||
+	    !is_power_of_2(dcr->blk_size)) {
+		dev_err(dev, "DC region %d invalid block size; %#llx\n",
+			index, dcr->blk_size);
+		return -EINVAL;
+	}
+
+	dev_dbg(dev,
+		"DC region %s base %#llx length %#llx block size %#llx\n",
+		dcr->name, dcr->base, dcr->decode_len, dcr->blk_size);
+
+	return 0;
+}
+
+/* Returns the number of regions in dc_resp or -ERRNO */
+static int cxl_get_dc_config(struct cxl_memdev_state *mds, u8 start_region,
+			     struct cxl_mbox_get_dc_config_out *dc_resp,
+			     size_t dc_resp_size)
+{
+	struct cxl_mbox_get_dc_config_in get_dc = (struct cxl_mbox_get_dc_config_in) {
+		.region_count = CXL_MAX_DC_REGION,
+		.start_region_index = start_region,
+	};
+	struct cxl_mbox_cmd mbox_cmd = (struct cxl_mbox_cmd) {
+		.opcode = CXL_MBOX_OP_GET_DC_CONFIG,
+		.payload_in = &get_dc,
+		.size_in = sizeof(get_dc),
+		.size_out = dc_resp_size,
+		.payload_out = dc_resp,
+		.min_out = 1,
+	};
+	struct device *dev = mds->cxlds.dev;
+	int rc;
+
+	rc = cxl_internal_send_cmd(&mds->cxlds.cxl_mbox, &mbox_cmd);
+	if (rc < 0)
+		return rc;
+
+	dev_dbg(dev, "Read %d/%d DC regions\n",
+		dc_resp->regions_returned, dc_resp->avail_region_count);
+	return dc_resp->regions_returned;
+}
+
+/**
+ * cxl_dev_dynamic_capacity_identify() - Reads the dynamic capacity
+ *					 information from the device.
+ * @mds: The memory device state
+ *
+ * Read Dynamic Capacity information from the device and populate the state
+ * structures for later use.
+ *
+ * Return: 0 if identify was executed successfully, -ERRNO on error.
+ */
+int cxl_dev_dynamic_capacity_identify(struct cxl_memdev_state *mds)
+{
+	size_t dc_resp_size = mds->cxlds.cxl_mbox.payload_size;
+	struct device *dev = mds->cxlds.dev;
+	u8 start_region, i;
+
+	if (!cxl_dcd_supported(mds)) {
+		dev_dbg(dev, "DCD not supported\n");
+		return 0;
+	}
+
+	struct cxl_mbox_get_dc_config_out *dc_resp __free(kfree) =
+					kvmalloc(dc_resp_size, GFP_KERNEL);
+	if (!dc_resp)
+		return -ENOMEM;
+
+	start_region = 0;
+	do {
+		int rc, j;
+
+		rc = cxl_get_dc_config(mds, start_region, dc_resp, dc_resp_size);
+		if (rc < 0) {
+			dev_err(dev, "Failed to get DC config: %d\n", rc);
+			return rc;
+		}
+
+		mds->nr_dc_region += rc;
+
+		if (mds->nr_dc_region < 1 || mds->nr_dc_region > CXL_MAX_DC_REGION) {
+			dev_err(dev, "Invalid num of dynamic capacity regions %d\n",
+				mds->nr_dc_region);
+			return -EINVAL;
+		}
+
+		for (i = start_region, j = 0; i < mds->nr_dc_region; i++, j++) {
+			rc = cxl_dc_save_region_info(mds, i, &dc_resp->region[j]);
+			if (rc)
+				return rc;
+		}
+
+		start_region = mds->nr_dc_region;
+
+	} while (mds->nr_dc_region < dc_resp->avail_region_count);
+
+	mds->dynamic_bytes =
+		mds->dc_region[mds->nr_dc_region - 1].base +
+		mds->dc_region[mds->nr_dc_region - 1].decode_len -
+		mds->dc_region[0].base;
+	dev_dbg(dev, "Total dynamic range: %#llx\n", mds->dynamic_bytes);
+
+	return 0;
+}
+EXPORT_SYMBOL_NS_GPL(cxl_dev_dynamic_capacity_identify, CXL);
+
 static int add_dpa_res(struct device *dev, struct resource *parent,
 		       struct resource *res, resource_size_t start,
 		       resource_size_t size, const char *type)
@@ -1304,8 +1452,15 @@ int cxl_mem_create_range_info(struct cxl_memdev_state *mds)
 {
 	struct cxl_dev_state *cxlds = &mds->cxlds;
 	struct device *dev = cxlds->dev;
+	size_t untenanted_mem;
 	int rc;
 
+	mds->total_bytes = mds->static_bytes;
+	if (mds->nr_dc_region) {
+		untenanted_mem = mds->dc_region[0].base - mds->static_bytes;
+		mds->total_bytes += untenanted_mem + mds->dynamic_bytes;
+	}
+
 	if (!cxlds->media_ready) {
 		cxlds->dpa_res = DEFINE_RES_MEM(0, 0);
 		cxlds->ram_res = DEFINE_RES_MEM(0, 0);
@@ -1315,6 +1470,15 @@ int cxl_mem_create_range_info(struct cxl_memdev_state *mds)
 
 	cxlds->dpa_res = DEFINE_RES_MEM(0, mds->total_bytes);
 
+	for (int i = 0; i < mds->nr_dc_region; i++) {
+		struct cxl_dc_region_info *dcr = &mds->dc_region[i];
+
+		rc = add_dpa_res(dev, &cxlds->dpa_res, &cxlds->dc_res[i],
+				 dcr->base, dcr->decode_len, dcr->name);
+		if (rc)
+			return rc;
+	}
+
 	if (mds->partition_align_bytes == 0) {
 		rc = add_dpa_res(dev, &cxlds->dpa_res, &cxlds->ram_res, 0,
 				 mds->volatile_only_bytes, "ram");
diff --git a/drivers/cxl/cxlmem.h b/drivers/cxl/cxlmem.h
index e8907c403edb..0690b917b1e0 100644
--- a/drivers/cxl/cxlmem.h
+++ b/drivers/cxl/cxlmem.h
@@ -403,6 +403,7 @@ enum cxl_devtype {
 	CXL_DEVTYPE_CLASSMEM,
 };
 
+#define CXL_MAX_DC_REGION 8
 /**
  * struct cxl_dpa_perf - DPA performance property entry
  * @dpa_range: range for DPA address
@@ -434,6 +435,8 @@ struct cxl_dpa_perf {
  * @dpa_res: Overall DPA resource tree for the device
  * @pmem_res: Active Persistent memory capacity configuration
  * @ram_res: Active Volatile memory capacity configuration
+ * @dc_res: Active Dynamic Capacity memory configuration for each possible
+ *          region
  * @serial: PCIe Device Serial Number
  * @type: Generic Memory Class device or Vendor Specific Memory device
  * @cxl_mbox: CXL mailbox context
@@ -449,11 +452,23 @@ struct cxl_dev_state {
 	struct resource dpa_res;
 	struct resource pmem_res;
 	struct resource ram_res;
+	struct resource dc_res[CXL_MAX_DC_REGION];
 	u64 serial;
 	enum cxl_devtype type;
 	struct cxl_mailbox cxl_mbox;
 };
 
+#define CXL_DC_REGION_STRLEN 8
+struct cxl_dc_region_info {
+	u64 base;
+	u64 decode_len;
+	u64 len;
+	u64 blk_size;
+	u32 dsmad_handle;
+	u8 flags;
+	u8 name[CXL_DC_REGION_STRLEN];
+};
+
 static inline struct cxl_dev_state *mbox_to_cxlds(struct cxl_mailbox *cxl_mbox)
 {
 	return dev_get_drvdata(cxl_mbox->host);
@@ -473,7 +488,9 @@ static inline struct cxl_dev_state *mbox_to_cxlds(struct cxl_mailbox *cxl_mbox)
  * @dcd_cmds: List of DCD commands implemented by memory device
  * @enabled_cmds: Hardware commands found enabled in CEL.
  * @exclusive_cmds: Commands that are kernel-internal only
- * @total_bytes: sum of all possible capacities
+ * @total_bytes: length of all possible capacities
+ * @static_bytes: length of possible static RAM and PMEM partitions
+ * @dynamic_bytes: length of possible DC partitions (DC Regions)
  * @volatile_only_bytes: hard volatile capacity
  * @persistent_only_bytes: hard persistent capacity
  * @partition_align_bytes: alignment size for partition-able capacity
@@ -483,6 +500,8 @@ static inline struct cxl_dev_state *mbox_to_cxlds(struct cxl_mailbox *cxl_mbox)
  * @next_persistent_bytes: persistent capacity change pending device reset
  * @ram_perf: performance data entry matched to RAM partition
  * @pmem_perf: performance data entry matched to PMEM partition
+ * @nr_dc_region: number of DC regions implemented in the memory device
+ * @dc_region: array containing info about the DC regions
  * @event: event log driver state
  * @poison: poison driver state info
  * @security: security driver state info
@@ -499,6 +518,8 @@ struct cxl_memdev_state {
 	DECLARE_BITMAP(enabled_cmds, CXL_MEM_COMMAND_ID_MAX);
 	DECLARE_BITMAP(exclusive_cmds, CXL_MEM_COMMAND_ID_MAX);
 	u64 total_bytes;
+	u64 static_bytes;
+	u64 dynamic_bytes;
 	u64 volatile_only_bytes;
 	u64 persistent_only_bytes;
 	u64 partition_align_bytes;
@@ -510,6 +531,9 @@ struct cxl_memdev_state {
 	struct cxl_dpa_perf ram_perf;
 	struct cxl_dpa_perf pmem_perf;
 
+	u8 nr_dc_region;
+	struct cxl_dc_region_info dc_region[CXL_MAX_DC_REGION];
+
 	struct cxl_event_state event;
 	struct cxl_poison_state poison;
 	struct cxl_security_state security;
@@ -708,6 +732,32 @@ struct cxl_mbox_set_partition_info {
 
 #define  CXL_SET_PARTITION_IMMEDIATE_FLAG	BIT(0)
 
+/* See CXL 3.1 Table 8-163 get dynamic capacity config Input Payload */
+struct cxl_mbox_get_dc_config_in {
+	u8 region_count;
+	u8 start_region_index;
+} __packed;
+
+/* See CXL 3.1 Table 8-164 get dynamic capacity config Output Payload */
+struct cxl_mbox_get_dc_config_out {
+	u8 avail_region_count;
+	u8 regions_returned;
+	u8 rsvd[6];
+	/* See CXL 3.1 Table 8-165 */
+	struct cxl_dc_region_config {
+		__le64 region_base;
+		__le64 region_decode_length;
+		__le64 region_length;
+		__le64 region_block_size;
+		__le32 region_dsmad_handle;
+		u8 flags;
+		u8 rsvd[3];
+	} __packed region[];
+	/* Trailing fields unused */
+} __packed;
+#define CXL_DYNAMIC_CAPACITY_SANITIZE_ON_RELEASE_FLAG BIT(0)
+#define CXL_DCD_BLOCK_LINE_SIZE 0x40
+
 /* Set Timestamp CXL 3.0 Spec 8.2.9.4.2 */
 struct cxl_mbox_set_timestamp_in {
 	__le64 timestamp;
@@ -831,6 +881,7 @@ 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);
+int cxl_dev_dynamic_capacity_identify(struct cxl_memdev_state *mds);
 int cxl_await_media_ready(struct cxl_dev_state *cxlds);
 int cxl_enumerate_cmds(struct cxl_memdev_state *mds);
 int cxl_mem_create_range_info(struct cxl_memdev_state *mds);
@@ -844,6 +895,17 @@ void cxl_event_trace_record(const struct cxl_memdev *cxlmd,
 			    enum cxl_event_log_type type,
 			    enum cxl_event_type event_type,
 			    const uuid_t *uuid, union cxl_event *evt);
+
+static inline bool cxl_dcd_supported(struct cxl_memdev_state *mds)
+{
+	return test_bit(CXL_DCD_ENABLED_GET_CONFIG, mds->dcd_cmds);
+}
+
+static inline void cxl_disable_dcd(struct cxl_memdev_state *mds)
+{
+	clear_bit(CXL_DCD_ENABLED_GET_CONFIG, mds->dcd_cmds);
+}
+
 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 0ccd6fd98b9d..fc5ab74448cc 100644
--- a/drivers/cxl/pci.c
+++ b/drivers/cxl/pci.c
@@ -899,6 +899,10 @@ static int cxl_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 	if (rc)
 		return rc;
 
+	rc = cxl_dev_dynamic_capacity_identify(mds);
+	if (rc)
+		cxl_disable_dcd(mds);
+
 	rc = cxl_mem_create_range_info(mds);
 	if (rc)
 		return rc;

-- 
2.46.0

On Mon, 07 Oct 2024 18:16:14 -0500
ira.weiny@intel.com wrote:

> From: Navneet Singh <navneet.singh@intel.com>
> 
> Devices which optionally support Dynamic Capacity (DC) are configured
> via mailbox commands.  CXL 3.1 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 3.1 section
> 8.2.9.9.9 (opcodes 48XXh) to read and store the DCD configuration
> information.  Disable DCD if DCD is not supported.  Leverage the Get DC
> Configuration command supported bit to indicate if DCD support.
> 
> 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.
> 
> Cc: "Li, Ming" <ming4.li@intel.com>
> Signed-off-by: Navneet Singh <navneet.singh@intel.com>
> Co-developed-by: Ira Weiny <ira.weiny@intel.com>
> Signed-off-by: Ira Weiny <ira.weiny@intel.com>

Looks fine to me.  Trivial comment inline
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>



> diff --git a/drivers/cxl/cxlmem.h b/drivers/cxl/cxlmem.h
> index e8907c403edb..0690b917b1e0 100644
> --- a/drivers/cxl/cxlmem.h
> +++ b/drivers/cxl/cxlmem.h
...

> +/* See CXL 3.1 Table 8-164 get dynamic capacity config Output Payload */
> +struct cxl_mbox_get_dc_config_out {
> +	u8 avail_region_count;
> +	u8 regions_returned;
> +	u8 rsvd[6];
> +	/* See CXL 3.1 Table 8-165 */
> +	struct cxl_dc_region_config {
> +		__le64 region_base;
> +		__le64 region_decode_length;
> +		__le64 region_length;
> +		__le64 region_block_size;
> +		__le32 region_dsmad_handle;
> +		u8 flags;
> +		u8 rsvd[3];
> +	} __packed region[];

Could throw in a __counted_by I think?

> +	/* Trailing fields unused */
> +} __packed;
> +#define CXL_DYNAMIC_CAPACITY_SANITIZE_ON_RELEASE_FLAG BIT(0)
> +#define CXL_DCD_BLOCK_LINE_SIZE 0x40

Jonathan Cameron wrote:
> On Mon, 07 Oct 2024 18:16:14 -0500
> ira.weiny@intel.com wrote:
> 
> > From: Navneet Singh <navneet.singh@intel.com>
> > 
> > Devices which optionally support Dynamic Capacity (DC) are configured
> > via mailbox commands.  CXL 3.1 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 3.1 section
> > 8.2.9.9.9 (opcodes 48XXh) to read and store the DCD configuration
> > information.  Disable DCD if DCD is not supported.  Leverage the Get DC
> > Configuration command supported bit to indicate if DCD support.
> > 
> > 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.
> > 
> > Cc: "Li, Ming" <ming4.li@intel.com>
> > Signed-off-by: Navneet Singh <navneet.singh@intel.com>
> > Co-developed-by: Ira Weiny <ira.weiny@intel.com>
> > Signed-off-by: Ira Weiny <ira.weiny@intel.com>
> 
> Looks fine to me.  Trivial comment inline

Thanks.

> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> 
> 
> 
> > diff --git a/drivers/cxl/cxlmem.h b/drivers/cxl/cxlmem.h
> > index e8907c403edb..0690b917b1e0 100644
> > --- a/drivers/cxl/cxlmem.h
> > +++ b/drivers/cxl/cxlmem.h
> ...
> 
> > +/* See CXL 3.1 Table 8-164 get dynamic capacity config Output Payload */
> > +struct cxl_mbox_get_dc_config_out {
> > +	u8 avail_region_count;
> > +	u8 regions_returned;
> > +	u8 rsvd[6];
> > +	/* See CXL 3.1 Table 8-165 */
> > +	struct cxl_dc_region_config {
> > +		__le64 region_base;
> > +		__le64 region_decode_length;
> > +		__le64 region_length;
> > +		__le64 region_block_size;
> > +		__le32 region_dsmad_handle;
> > +		u8 flags;
> > +		u8 rsvd[3];
> > +	} __packed region[];
> 
> Could throw in a __counted_by I think?

I was not sure if this would work considering this is coming from the hardware.
From what I have read I think it will but only because the region count can't
be byte swapped.

Is this something we want to do with structs coming from hardware when we can?

Ira

On Sun, 13 Oct 2024 19:05:11 -0500
Ira Weiny <ira.weiny@intel.com> wrote:

> Jonathan Cameron wrote:
> > On Mon, 07 Oct 2024 18:16:14 -0500
> > ira.weiny@intel.com wrote:
> >   
> > > From: Navneet Singh <navneet.singh@intel.com>
> > > 
> > > Devices which optionally support Dynamic Capacity (DC) are configured
> > > via mailbox commands.  CXL 3.1 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 3.1 section
> > > 8.2.9.9.9 (opcodes 48XXh) to read and store the DCD configuration
> > > information.  Disable DCD if DCD is not supported.  Leverage the Get DC
> > > Configuration command supported bit to indicate if DCD support.
> > > 
> > > 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.
> > > 
> > > Cc: "Li, Ming" <ming4.li@intel.com>
> > > Signed-off-by: Navneet Singh <navneet.singh@intel.com>
> > > Co-developed-by: Ira Weiny <ira.weiny@intel.com>
> > > Signed-off-by: Ira Weiny <ira.weiny@intel.com>  
> > 
> > Looks fine to me.  Trivial comment inline  
> 
> Thanks.
> 
> > Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> > 
> > 
> >   
> > > diff --git a/drivers/cxl/cxlmem.h b/drivers/cxl/cxlmem.h
> > > index e8907c403edb..0690b917b1e0 100644
> > > --- a/drivers/cxl/cxlmem.h
> > > +++ b/drivers/cxl/cxlmem.h  
> > ...
> >   
> > > +/* See CXL 3.1 Table 8-164 get dynamic capacity config Output Payload */
> > > +struct cxl_mbox_get_dc_config_out {
> > > +	u8 avail_region_count;
> > > +	u8 regions_returned;
> > > +	u8 rsvd[6];
> > > +	/* See CXL 3.1 Table 8-165 */
> > > +	struct cxl_dc_region_config {
> > > +		__le64 region_base;
> > > +		__le64 region_decode_length;
> > > +		__le64 region_length;
> > > +		__le64 region_block_size;
> > > +		__le32 region_dsmad_handle;
> > > +		u8 flags;
> > > +		u8 rsvd[3];
> > > +	} __packed region[];  
> > 
> > Could throw in a __counted_by I think?  
> 
> I was not sure if this would work considering this is coming from the hardware.
> From what I have read I think it will but only because the region count can't
> be byte swapped.

__counted_by_le() deals potentially larger values by just making
the __counted_by go away on big endian architectures.


> 
> Is this something we want to do with structs coming from hardware when we can?

I think we still do.  Gustavo, Kees?
> Ira
>

On Wed, Oct 16, 2024 at 04:54:15PM +0100, Jonathan Cameron wrote:
> On Sun, 13 Oct 2024 19:05:11 -0500
> Ira Weiny <ira.weiny@intel.com> wrote:
> 
> > Jonathan Cameron wrote:
> > > On Mon, 07 Oct 2024 18:16:14 -0500
> > > ira.weiny@intel.com wrote:
> > >   
> > > > From: Navneet Singh <navneet.singh@intel.com>
> > > > 
> > > > Devices which optionally support Dynamic Capacity (DC) are configured
> > > > via mailbox commands.  CXL 3.1 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 3.1 section
> > > > 8.2.9.9.9 (opcodes 48XXh) to read and store the DCD configuration
> > > > information.  Disable DCD if DCD is not supported.  Leverage the Get DC
> > > > Configuration command supported bit to indicate if DCD support.
> > > > 
> > > > 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.
> > > > 
> > > > Cc: "Li, Ming" <ming4.li@intel.com>
> > > > Signed-off-by: Navneet Singh <navneet.singh@intel.com>
> > > > Co-developed-by: Ira Weiny <ira.weiny@intel.com>
> > > > Signed-off-by: Ira Weiny <ira.weiny@intel.com>  
> > > 
> > > Looks fine to me.  Trivial comment inline  
> > 
> > Thanks.
> > 
> > > Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> > > 
> > > 
> > >   
> > > > diff --git a/drivers/cxl/cxlmem.h b/drivers/cxl/cxlmem.h
> > > > index e8907c403edb..0690b917b1e0 100644
> > > > --- a/drivers/cxl/cxlmem.h
> > > > +++ b/drivers/cxl/cxlmem.h  
> > > ...
> > >   
> > > > +/* See CXL 3.1 Table 8-164 get dynamic capacity config Output Payload */
> > > > +struct cxl_mbox_get_dc_config_out {
> > > > +	u8 avail_region_count;
> > > > +	u8 regions_returned;
> > > > +	u8 rsvd[6];
> > > > +	/* See CXL 3.1 Table 8-165 */
> > > > +	struct cxl_dc_region_config {
> > > > +		__le64 region_base;
> > > > +		__le64 region_decode_length;
> > > > +		__le64 region_length;
> > > > +		__le64 region_block_size;
> > > > +		__le32 region_dsmad_handle;
> > > > +		u8 flags;
> > > > +		u8 rsvd[3];
> > > > +	} __packed region[];  
> > > 
> > > Could throw in a __counted_by I think?  
> > 
> > I was not sure if this would work considering this is coming from the hardware.
> > From what I have read I think it will but only because the region count can't
> > be byte swapped.
> 
> __counted_by_le() deals potentially larger values by just making
> the __counted_by go away on big endian architectures.
> 
> 
> > 
> > Is this something we want to do with structs coming from hardware when we can?
> 
> I think we still do.  Gustavo, Kees?

As long as "regions_returned" got correctly set by hardware before
anything in the kernel touches the "region" array, it can totally be
used by a __counted_by annotation.

-- 
Kees Cook