Commit 2c866903 authored by Dan Williams's avatar Dan Williams
Browse files

cxl/hdm: Add 'mode' attribute to decoder objects 



Recall that the Device Physical Address (DPA) space of a CXL Memory
Expander is potentially partitioned into a volatile and persistent
portion. A decoder maps a Host Physical Address (HPA) range to a DPA
range and that translation depends on the value of all previous (lower
instance number) decoders before the current one.

In preparation for allowing dynamic provisioning of regions, decoders
need an ABI to indicate which DPA partition a decoder targets. This ABI
needs to be prepared for the possibility that some other agent committed
and locked a decoder that spans the partition boundary.

Add 'decoderX.Y/mode' to endpoint decoders that indicates which
partition 'ram' / 'pmem' the decoder targets, or 'mixed' if the decoder
currently spans the partition boundary.

Reviewed-by: default avatarJonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/165603881967.551046.6007594190951596439.stgit@dwillia2-xfh


Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
parent 9c57cde0

Documentation/ABI/testing/sysfs-bus-cxl

+16 −0
Original line number Diff line number Diff line
@@ -190,3 +190,19 @@ Description: 
		found to support CDAT data.  If it is present and the length of

		the data is 0 reading the CDAT data failed.  Otherwise the CDAT

		data is reported.





What:		/sys/bus/cxl/devices/decoderX.Y/mode

Date:		May, 2022

KernelVersion:	v5.20

Contact:	linux-cxl@vger.kernel.org

Description:

		(RO) When a CXL decoder is of devtype "cxl_decoder_endpoint" it

		translates from a host physical address range, to a device local

		address range. Device-local address ranges are further split

		into a 'ram' (volatile memory) range and 'pmem' (persistent

		memory) range. The 'mode' attribute emits one of 'ram', 'pmem',

		'mixed', or 'none'. The 'mixed' indication is for error cases

		when a decoder straddles the volatile/persistent partition

		boundary, and 'none' indicates the decoder is not actively

		decoding, or no DPA allocation policy has been set.

drivers/cxl/core/hdm.c

+10 −0
Original line number Diff line number Diff line
@@ -226,6 +226,16 @@ static int __cxl_dpa_reserve(struct cxl_endpoint_decoder *cxled, 
	cxled->dpa_res = res;

	cxled->skip = skipped;



	if (resource_contains(&cxlds->pmem_res, res))

		cxled->mode = CXL_DECODER_PMEM;

	else if (resource_contains(&cxlds->ram_res, res))

		cxled->mode = CXL_DECODER_RAM;

	else {

		dev_dbg(dev, "decoder%d.%d: %pr mixed\n", port->id,

			cxled->cxld.id, cxled->dpa_res);

		cxled->mode = CXL_DECODER_MIXED;

	}



	return 0;

}

drivers/cxl/core/port.c

+20 −0
Original line number Diff line number Diff line
@@ -172,6 +172,25 @@ static ssize_t target_list_show(struct device *dev, 
}

static DEVICE_ATTR_RO(target_list);



static ssize_t mode_show(struct device *dev, struct device_attribute *attr,

			 char *buf)

{

	struct cxl_endpoint_decoder *cxled = to_cxl_endpoint_decoder(dev);



	switch (cxled->mode) {

	case CXL_DECODER_RAM:

		return sysfs_emit(buf, "ram\n");

	case CXL_DECODER_PMEM:

		return sysfs_emit(buf, "pmem\n");

	case CXL_DECODER_NONE:

		return sysfs_emit(buf, "none\n");

	case CXL_DECODER_MIXED:

	default:

		return sysfs_emit(buf, "mixed\n");

	}

}

static DEVICE_ATTR_RO(mode);



static struct attribute *cxl_decoder_base_attrs[] = {

	&dev_attr_start.attr,

	&dev_attr_size.attr,
@@ -222,6 +241,7 @@ static const struct attribute_group *cxl_decoder_switch_attribute_groups[] = { 


static struct attribute *cxl_decoder_endpoint_attrs[] = {

	&dev_attr_target_type.attr,

	&dev_attr_mode.attr,

	NULL,

};

drivers/cxl/cxl.h

+9 −0
Original line number Diff line number Diff line
@@ -241,16 +241,25 @@ struct cxl_decoder { 
	unsigned long flags;

};



enum cxl_decoder_mode {

	CXL_DECODER_NONE,

	CXL_DECODER_RAM,

	CXL_DECODER_PMEM,

	CXL_DECODER_MIXED,

};



/**

 * struct cxl_endpoint_decoder - Endpoint  / SPA to DPA decoder

 * @cxld: base cxl_decoder_object

 * @dpa_res: actively claimed DPA span of this decoder

 * @skip: offset into @dpa_res where @cxld.hpa_range maps

 * @mode: which memory type / access-mode-partition this decoder targets

 */

struct cxl_endpoint_decoder {

	struct cxl_decoder cxld;

	struct resource *dpa_res;

	resource_size_t skip;

	enum cxl_decoder_mode mode;

};



/**