[PATCH 07/26] cxl/port: Add dynamic capacity size support to endpoint decoders

[ira.weiny@intel.com]

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

To support Dynamic Capacity Devices (DCD) endpoint decoders will need to
map DC partitions (regions).  In addition to assigning the size of the
DC partition, the decoder must assign any skip value from the previous
decoder.  This must be done within a contiguous DPA space.

Two complications arise with Dynamic Capacity regions which did not
exist with Ram and PMEM partitions.  First, gaps in the DPA space can
exist between and around the DC Regions.  Second, the Linux resource
tree does not allow a resource to be marked across existing nodes within
a tree.

For clarity, below is an example of an 60GB device with 10GB of RAM,
10GB of PMEM and 10GB for each of 2 DC Regions.  The desired CXL mapping
is 5GB of RAM, 5GB of PMEM, and all 10GB of DC1.

     DPA RANGE
     (dpa_res)
0GB        10GB       20GB       30GB       40GB       50GB       60GB
|----------|----------|----------|----------|----------|----------|

RAM         PMEM                  DC0                   DC1
 (ram_res)  (pmem_res)            (dc_res[0])           (dc_res[1])
|----------|----------|   <gap>  |----------|   <gap>  |----------|

 RAM        PMEM                                        DC1
|XXXXX|----|XXXXX|----|----------|----------|----------|XXXXXXXXXX|
0GB   5GB  10GB  15GB 20GB       30GB       40GB       50GB       60GB

The previous skip resource between RAM and PMEM was always a child of
the RAM resource and fit nicely [see (S) below].  Because of this
simplicity this skip resource reference was not stored in any CXL state.
On release the skip range could be calculated based on the endpoint
decoders stored values.

Now when DC1 is being mapped 4 skip resources must be created as
children.  One for the PMEM resource (A), two of the parent DPA resource
(B,D), and one more child of the DC0 resource (C).

0GB        10GB       20GB       30GB       40GB       50GB       60GB
|----------|----------|----------|----------|----------|----------|
                           |                     |
|----------|----------|    |     |----------|    |     |----------|
        |          |       |          |          |
       (S)        (A)     (B)        (C)        (D)
	v          v       v          v          v
|XXXXX|----|XXXXX|----|----------|----------|----------|XXXXXXXXXX|
       skip       skip  skip        skip      skip

Expand the calculation of DPA freespace and enhance the logic to support
mapping/unmapping DC DPA space.  To track the potential of multiple skip
resources an xarray is attached to the endpoint decoder.  The existing
algorithm between RAM and PMEM is consolidated within the new one to
streamline the code even though the result is the storage of a single
skip resource in the xarray.

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 for v1:
[iweiny: Update cover letter]
---
 drivers/cxl/core/hdm.c  | 192 +++++++++++++++++++++++++++++++++++++++++++-----
 drivers/cxl/core/port.c |   2 +
 drivers/cxl/cxl.h       |   2 +
 3 files changed, 179 insertions(+), 17 deletions(-)

diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
index e22b6f4f7145..da7d58184490 100644
--- a/drivers/cxl/core/hdm.c
+++ b/drivers/cxl/core/hdm.c
@@ -210,6 +210,25 @@ void cxl_dpa_debug(struct seq_file *file, struct cxl_dev_state *cxlds)
 }
 EXPORT_SYMBOL_NS_GPL(cxl_dpa_debug, CXL);
 
+static void cxl_skip_release(struct cxl_endpoint_decoder *cxled)
+{
+	struct cxl_dev_state *cxlds = cxled_to_memdev(cxled)->cxlds;
+	struct cxl_port *port = cxled_to_port(cxled);
+	struct device *dev = &port->dev;
+	unsigned long index;
+	void *entry;
+
+	xa_for_each(&cxled->skip_res, index, entry) {
+		struct resource *res = entry;
+
+		dev_dbg(dev, "decoder%d.%d: releasing skipped space; %pr\n",
+			port->id, cxled->cxld.id, res);
+		__release_region(&cxlds->dpa_res, res->start,
+				 resource_size(res));
+		xa_erase(&cxled->skip_res, index);
+	}
+}
+
 /*
  * Must be called in a context that synchronizes against this decoder's
  * port ->remove() callback (like an endpoint decoder sysfs attribute)
@@ -220,15 +239,11 @@ static void __cxl_dpa_release(struct cxl_endpoint_decoder *cxled)
 	struct cxl_port *port = cxled_to_port(cxled);
 	struct cxl_dev_state *cxlds = cxlmd->cxlds;
 	struct resource *res = cxled->dpa_res;
-	resource_size_t skip_start;
 
 	lockdep_assert_held_write(&cxl_dpa_rwsem);
 
-	/* save @skip_start, before @res is released */
-	skip_start = res->start - cxled->skip;
 	__release_region(&cxlds->dpa_res, res->start, resource_size(res));
-	if (cxled->skip)
-		__release_region(&cxlds->dpa_res, skip_start, cxled->skip);
+	cxl_skip_release(cxled);
 	cxled->skip = 0;
 	cxled->dpa_res = NULL;
 	put_device(&cxled->cxld.dev);
@@ -263,6 +278,100 @@ static int dc_mode_to_region_index(enum cxl_decoder_mode mode)
 	return mode - CXL_DECODER_DC0;
 }
 
+static int cxl_request_skip(struct cxl_endpoint_decoder *cxled,
+			    resource_size_t skip_base, resource_size_t skip_len)
+{
+	struct cxl_dev_state *cxlds = cxled_to_memdev(cxled)->cxlds;
+	const char *name = dev_name(&cxled->cxld.dev);
+	struct cxl_port *port = cxled_to_port(cxled);
+	struct resource *dpa_res = &cxlds->dpa_res;
+	struct device *dev = &port->dev;
+	struct resource *res;
+	int rc;
+
+	res = __request_region(dpa_res, skip_base, skip_len, name, 0);
+	if (!res)
+		return -EBUSY;
+
+	rc = xa_insert(&cxled->skip_res, skip_base, res, GFP_KERNEL);
+	if (rc) {
+		__release_region(dpa_res, skip_base, skip_len);
+		return rc;
+	}
+
+	dev_dbg(dev, "decoder%d.%d: skipped space; %pr\n",
+		port->id, cxled->cxld.id, res);
+	return 0;
+}
+
+static int cxl_reserve_dpa_skip(struct cxl_endpoint_decoder *cxled,
+				resource_size_t base, resource_size_t skipped)
+{
+	struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
+	struct cxl_port *port = cxled_to_port(cxled);
+	struct cxl_dev_state *cxlds = cxlmd->cxlds;
+	resource_size_t skip_base = base - skipped;
+	struct device *dev = &port->dev;
+	resource_size_t skip_len = 0;
+	int rc, index;
+
+	if (resource_size(&cxlds->ram_res) && skip_base <= cxlds->ram_res.end) {
+		skip_len = cxlds->ram_res.end - skip_base + 1;
+		rc = cxl_request_skip(cxled, skip_base, skip_len);
+		if (rc)
+			return rc;
+		skip_base += skip_len;
+	}
+
+	if (skip_base == base) {
+		dev_dbg(dev, "skip done ram!\n");
+		return 0;
+	}
+
+	if (resource_size(&cxlds->pmem_res) &&
+	    skip_base <= cxlds->pmem_res.end) {
+		skip_len = cxlds->pmem_res.end - skip_base + 1;
+		rc = cxl_request_skip(cxled, skip_base, skip_len);
+		if (rc)
+			return rc;
+		skip_base += skip_len;
+	}
+
+	index = dc_mode_to_region_index(cxled->mode);
+	for (int i = 0; i <= index; i++) {
+		struct resource *dcr = &cxlds->dc_res[i];
+
+		if (skip_base < dcr->start) {
+			skip_len = dcr->start - skip_base;
+			rc = cxl_request_skip(cxled, skip_base, skip_len);
+			if (rc)
+				return rc;
+			skip_base += skip_len;
+		}
+
+		if (skip_base == base) {
+			dev_dbg(dev, "skip done DC region %d!\n", i);
+			break;
+		}
+
+		if (resource_size(dcr) && skip_base <= dcr->end) {
+			if (skip_base > base) {
+				dev_err(dev, "Skip error DC region %d; skip_base %pa; base %pa\n",
+					i, &skip_base, &base);
+				return -ENXIO;
+			}
+
+			skip_len = dcr->end - skip_base + 1;
+			rc = cxl_request_skip(cxled, skip_base, skip_len);
+			if (rc)
+				return rc;
+			skip_base += skip_len;
+		}
+	}
+
+	return 0;
+}
+
 static int __cxl_dpa_reserve(struct cxl_endpoint_decoder *cxled,
 			     resource_size_t base, resource_size_t len,
 			     resource_size_t skipped)
@@ -300,13 +409,12 @@ static int __cxl_dpa_reserve(struct cxl_endpoint_decoder *cxled,
 	}
 
 	if (skipped) {
-		res = __request_region(&cxlds->dpa_res, base - skipped, skipped,
-				       dev_name(&cxled->cxld.dev), 0);
-		if (!res) {
-			dev_dbg(dev,
-				"decoder%d.%d: failed to reserve skipped space\n",
-				port->id, cxled->cxld.id);
-			return -EBUSY;
+		int rc = cxl_reserve_dpa_skip(cxled, base, skipped);
+
+		if (rc) {
+			dev_dbg(dev, "decoder%d.%d: failed to reserve skipped space; %pa - %pa\n",
+				port->id, cxled->cxld.id, &base, &skipped);
+			return rc;
 		}
 	}
 	res = __request_region(&cxlds->dpa_res, base, len,
@@ -314,14 +422,20 @@ static int __cxl_dpa_reserve(struct cxl_endpoint_decoder *cxled,
 	if (!res) {
 		dev_dbg(dev, "decoder%d.%d: failed to reserve allocation\n",
 			port->id, cxled->cxld.id);
-		if (skipped)
-			__release_region(&cxlds->dpa_res, base - skipped,
-					 skipped);
+		cxl_skip_release(cxled);
 		return -EBUSY;
 	}
 	cxled->dpa_res = res;
 	cxled->skip = skipped;
 
+	for (int mode = CXL_DECODER_DC0; mode <= CXL_DECODER_DC7; mode++) {
+		int index = dc_mode_to_region_index(mode);
+
+		if (resource_contains(&cxlds->dc_res[index], res)) {
+			cxled->mode = mode;
+			goto success;
+		}
+	}
 	if (resource_contains(&cxlds->pmem_res, res))
 		cxled->mode = CXL_DECODER_PMEM;
 	else if (resource_contains(&cxlds->ram_res, res))
@@ -332,6 +446,9 @@ static int __cxl_dpa_reserve(struct cxl_endpoint_decoder *cxled,
 		cxled->mode = CXL_DECODER_MIXED;
 	}
 
+success:
+	dev_dbg(dev, "decoder%d.%d: %pr mode: %d\n", port->id, cxled->cxld.id,
+		cxled->dpa_res, cxled->mode);
 	port->hdm_end++;
 	get_device(&cxled->cxld.dev);
 	return 0;
@@ -463,14 +580,14 @@ int cxl_dpa_set_mode(struct cxl_endpoint_decoder *cxled,
 
 int cxl_dpa_alloc(struct cxl_endpoint_decoder *cxled, unsigned long long size)
 {
+	resource_size_t free_ram_start, free_pmem_start, free_dc_start;
 	struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
-	resource_size_t free_ram_start, free_pmem_start;
 	struct cxl_port *port = cxled_to_port(cxled);
 	struct cxl_dev_state *cxlds = cxlmd->cxlds;
 	struct device *dev = &cxled->cxld.dev;
 	resource_size_t start, avail, skip;
 	struct resource *p, *last;
-	int rc;
+	int rc, dc_index;
 
 	down_write(&cxl_dpa_rwsem);
 	if (cxled->cxld.region) {
@@ -500,6 +617,21 @@ int cxl_dpa_alloc(struct cxl_endpoint_decoder *cxled, unsigned long long size)
 	else
 		free_pmem_start = cxlds->pmem_res.start;
 
+	/*
+	 * Limit each decoder to a single DC region to map memory with
+	 * different DSMAS entry.
+	 */
+	dc_index = dc_mode_to_region_index(cxled->mode);
+	if (dc_index >= 0) {
+		if (cxlds->dc_res[dc_index].child) {
+			dev_err(dev, "Cannot allocate DPA from DC Region: %d\n",
+				dc_index);
+			rc = -EINVAL;
+			goto out;
+		}
+		free_dc_start = cxlds->dc_res[dc_index].start;
+	}
+
 	if (cxled->mode == CXL_DECODER_RAM) {
 		start = free_ram_start;
 		avail = cxlds->ram_res.end - start + 1;
@@ -521,12 +653,38 @@ int cxl_dpa_alloc(struct cxl_endpoint_decoder *cxled, unsigned long long size)
 		else
 			skip_end = start - 1;
 		skip = skip_end - skip_start + 1;
+	} else if (cxl_decoder_mode_is_dc(cxled->mode)) {
+		resource_size_t skip_start, skip_end;
+
+		start = free_dc_start;
+		avail = cxlds->dc_res[dc_index].end - start + 1;
+		if ((resource_size(&cxlds->pmem_res) == 0) || !cxlds->pmem_res.child)
+			skip_start = free_ram_start;
+		else
+			skip_start = free_pmem_start;
+		/*
+		 * If any dc region is already mapped, then that allocation
+		 * already handled the RAM and PMEM skip.  Check for DC region
+		 * skip.
+		 */
+		for (int i = dc_index - 1; i >= 0 ; i--) {
+			if (cxlds->dc_res[i].child) {
+				skip_start = cxlds->dc_res[i].child->end + 1;
+				break;
+			}
+		}
+
+		skip_end = start - 1;
+		skip = skip_end - skip_start + 1;
 	} else {
 		dev_dbg(dev, "mode not set\n");
 		rc = -EINVAL;
 		goto out;
 	}
 
+	dev_dbg(dev, "DPA Allocation start: %pa len: %#llx Skip: %pa\n",
+		&start, size, &skip);
+
 	if (size > avail) {
 		dev_dbg(dev, "%pa exceeds available %s capacity: %pa\n", &size,
 			cxled->mode == CXL_DECODER_RAM ? "ram" : "pmem",
diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
index 80c0651794eb..036b61cb3007 100644
--- a/drivers/cxl/core/port.c
+++ b/drivers/cxl/core/port.c
@@ -434,6 +434,7 @@ static void cxl_endpoint_decoder_release(struct device *dev)
 	struct cxl_endpoint_decoder *cxled = to_cxl_endpoint_decoder(dev);
 
 	__cxl_decoder_release(&cxled->cxld);
+	xa_destroy(&cxled->skip_res);
 	kfree(cxled);
 }
 
@@ -1896,6 +1897,7 @@ struct cxl_endpoint_decoder *cxl_endpoint_decoder_alloc(struct cxl_port *port)
 		return ERR_PTR(-ENOMEM);
 
 	cxled->pos = -1;
+	xa_init(&cxled->skip_res);
 	cxld = &cxled->cxld;
 	rc = cxl_decoder_init(port, cxld);
 	if (rc)	 {
diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index 3b8935089c0c..15d418b3bc9b 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -441,6 +441,7 @@ enum cxl_decoder_state {
  * @cxld: base cxl_decoder_object
  * @dpa_res: actively claimed DPA span of this decoder
  * @skip: offset into @dpa_res where @cxld.hpa_range maps
+ * @skip_res: array of skipped resources from the previous decoder end
  * @mode: which memory type / access-mode-partition this decoder targets
  * @state: autodiscovery state
  * @pos: interleave position in @cxld.region
@@ -449,6 +450,7 @@ struct cxl_endpoint_decoder {
 	struct cxl_decoder cxld;
 	struct resource *dpa_res;
 	resource_size_t skip;
+	struct xarray skip_res;
 	enum cxl_decoder_mode mode;
 	enum cxl_decoder_state state;
 	int pos;

-- 
2.44.0