cxl/extent: Process dynamic partition events and realize region extents

A dynamic capacity device (DCD) sends events to signal the host for
changes in the availability of Dynamic Capacity (DC) memory.  These
events contain extents describing a DPA range and meta data for memory
to be added or removed.  Events may be sent from the device at any time.

Three types of events can be signaled, Add, Release, and Force Release.

On add, the host may accept or reject the memory being offered.  If no
region exists, or the extent is invalid, the extent should be rejected.
Add extent events may be grouped by a 'more' bit which indicates those
extents should be processed as a group.

On remove, the host can delay the response until the host is safely not
using the memory.  If no region exists the release can be sent
immediately.  The host may also release extents (or partial extents) at
any time.  Thus the 'more' bit grouping of release events is of less
value and can be ignored in favor of sending multiple release capacity
responses for groups of release events.

Force removal is intended as a mechanism between the FM and the device
and intended only when the host is unresponsive, out of sync, or
otherwise broken.  Purposely ignore force removal events.

Regions are made up of one or more devices which may be surfacing memory
to the host.  Once all devices in a region have surfaced an extent the
region can expose a corresponding extent for the user to consume.
Without interleaving a device extent forms a 1:1 relationship with the
region extent.  Immediately surface a region extent upon getting a
device extent.

Per the specification the device is allowed to offer or remove extents
at any time.  However, anticipated use cases can expect extents to be
offered, accepted, and removed in well defined chunks.

Simplify extent tracking with the following restrictions.

	1) Flag for removal any extent which overlaps a requested
	   release range.
	2) Refuse the offer of extents which overlap already accepted
	   memory ranges.
	3) Accept again a range which has already been accepted by the
	   host.  Eating duplicates serves three purposes.
	   3a) This simplifies the code if the device should get out of
	       sync with the host.  And it should be safe to acknowledge
	       the extent again.
	   3b) This simplifies the code to process existing extents if
	       the extent list should change while the extent list is
	       being read.
	   3c) Duplicates for a given partition which are seen during a
	       race between the hardware surfacing an extent and the cxl
	       dax driver scanning for existing extents will be ignored.

	   NOTE: Processing existing extents is done in a later patch.

Management of the region extent devices must be synchronized with
potential uses of the memory within the DAX layer.  Create region extent
devices as children of the cxl_dax_region device such that the DAX
region driver can co-drive them and synchronize with the DAX layer.
Synchronization and management is handled in a subsequent patch.

Tag support within the DAX layer is not yet supported.  To maintain
compatibility with legacy DAX/region processing only tags with a value
of 0 are allowed.  This defines existing DAX devices as having a 0 tag
which makes the most logical sense as a default.

Process DCD events and create region devices.

Based on an original patch by Navneet Singh.

Reviewed-by: Dave Jiang <[email protected]>
Reviewed-by: Li Ming <[email protected]>
Reviewed-by: Jonathan Cameron <[email protected]>
Signed-off-by: Ira Weiny <[email protected]>

---
Changes:
[iweiny: rebase]
[djbw: s/region/partition/]
[iweiny: Adapt to new partition arch]
[iweiny: s/tag/uuid/ throughout the code]

Author: weiny2

drivers/cxl/core/Makefile

@@ -17,6 +17,6 @@ cxl_core-y += cdat.o
 cxl_core-y += ras.o
 cxl_core-y += acpi.o
 cxl_core-$(CONFIG_TRACING) += trace.o
-cxl_core-$(CONFIG_CXL_REGION) += region.o
+cxl_core-$(CONFIG_CXL_REGION) += region.o extent.o
 cxl_core-$(CONFIG_CXL_MCE) += mce.o
 cxl_core-$(CONFIG_CXL_FEATURES) += features.o

drivers/cxl/core/core.h

@@ -45,12 +45,24 @@ struct cxl_region *cxl_dpa_to_region(const struct cxl_memdev *cxlmd, u64 dpa,
 u64 cxl_dpa_to_hpa(struct cxl_region *cxlr, const struct cxl_memdev *cxlmd,
 		   u64 dpa);
 
+int cxl_add_extent(struct cxl_memdev_state *mds, struct cxl_extent *extent);
+int cxl_rm_extent(struct cxl_memdev_state *mds, struct cxl_extent *extent);
 #else
 static inline u64 cxl_dpa_to_hpa(struct cxl_region *cxlr,
 				 const struct cxl_memdev *cxlmd, u64 dpa)
 {
 	return ULLONG_MAX;
 }
+static inline int cxl_add_extent(struct cxl_memdev_state *mds,
+				   struct cxl_extent *extent)
+{
+	return 0;
+}
+static inline int cxl_rm_extent(struct cxl_memdev_state *mds,
+				struct cxl_extent *extent)
+{
+	return 0;
+}
 static inline
 struct cxl_region *cxl_dpa_to_region(const struct cxl_memdev *cxlmd, u64 dpa,
 				     struct cxl_endpoint_decoder **cxled)
@@ -129,6 +141,7 @@ int cxl_update_hmat_access_coordinates(int nid, struct cxl_region *cxlr,
 bool cxl_need_node_perf_attrs_update(int nid);
 int cxl_port_get_switch_dport_bandwidth(struct cxl_port *port,
 					struct access_coordinate *c);
+void memdev_release_extent(struct cxl_memdev_state *mds, struct range *range);
 
 int cxl_ras_init(void);
 void cxl_ras_exit(void);