[PATCH v15 7/8] cxl/core: Enforce partition order/simplify partition calls

[Anisa Su <anisa.su887@gmail.com>]

From: Ira Weiny <iweiny@kernel.org>

Device partitions share one flat DPA space in a fixed order: static
volatile capacity at DPA 0, static persistent capacity immediately above
it, and dynamic capacity above all static capacity.  The static pair is
mandated by CXL r4.0 8.2.10.9.2.1 "Get Partition Info", Table 8-310: the
device "shall provide this volatile capacity starting at DPA 0" and
"shall provide this persistent capacity starting at the DPA immediately
following the volatile capacity".  Dynamic capacity has no such rule.
Table 8-347 only requires the region base to be 256M aligned, so placing
it directly above static capacity is a Linux requirement,
enforced by cxl_configure_dcd().

    DPA 0                                                     end
    +---------------+---------------+---------------------------+
    |      ram      |     pmem      |       dynamic_ram_1       |
    +---------------+---------------+---------------------------+
    part[0]         part[1]         part[2]

Signed-off-by: Ira Weiny <iweiny@kernel.org>
Co-developed-by: Anisa Su <anisa.su@samsung.com>
Signed-off-by: Anisa Su <anisa.su@samsung.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>
Reviewed-by: Alison Schofield <alison.schofield@intel.com>
---
 drivers/cxl/core/hdm.c    | 10 ++++++++++
 drivers/cxl/core/memdev.c | 32 +++++++++-----------------------
 drivers/cxl/cxlmem.h      |  9 +++------
 drivers/cxl/mem.c         |  2 +-
 include/cxl/cxl.h         | 20 ++++++++++++++++++++
 5 files changed, 43 insertions(+), 30 deletions(-)

diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
index 379540246333..ec5742debb52 100644
--- a/drivers/cxl/core/hdm.c
+++ b/drivers/cxl/core/hdm.c
@@ -470,6 +470,16 @@ int cxl_dpa_setup(struct cxl_dev_state *cxlds, const struct cxl_dpa_info *info)
 		return 0;
 	}
 
+	/* Verify partitions are in expected order. */
+	for (int i = 1; i < info->nr_partitions; i++) {
+		if (info->part[i].mode < info->part[i - 1].mode) {
+			dev_err(dev, "Partition order mismatch: %d (%s) follows %d (%s)\n",
+				i, cxl_mode_name(info->part[i].mode),
+				i - 1, cxl_mode_name(info->part[i - 1].mode));
+			return -EINVAL;
+		}
+	}
+
 	cxlds->dpa_res = DEFINE_RES_MEM(0, info->size);
 
 	for (int i = 0; i < info->nr_partitions; i++) {
diff --git a/drivers/cxl/core/memdev.c b/drivers/cxl/core/memdev.c
index 7aa79a1a53e4..3ad68341d294 100644
--- a/drivers/cxl/core/memdev.c
+++ b/drivers/cxl/core/memdev.c
@@ -77,20 +77,12 @@ static ssize_t label_storage_size_show(struct device *dev,
 }
 static DEVICE_ATTR_RO(label_storage_size);
 
-static resource_size_t cxl_ram_size(struct cxl_dev_state *cxlds)
-{
-	/* Static RAM is only expected at partition 0. */
-	if (cxlds->part[0].mode != CXL_PARTMODE_RAM)
-		return 0;
-	return resource_size(&cxlds->part[0].res);
-}
-
 static ssize_t ram_size_show(struct device *dev, struct device_attribute *attr,
 			     char *buf)
 {
 	struct cxl_memdev *cxlmd = to_cxl_memdev(dev);
 	struct cxl_dev_state *cxlds = cxlmd->cxlds;
-	unsigned long long len = cxl_ram_size(cxlds);
+	unsigned long long len = cxl_part_size(cxlds, CXL_PARTMODE_RAM);
 
 	return sysfs_emit(buf, "%#llx\n", len);
 }
@@ -103,7 +95,7 @@ static ssize_t pmem_size_show(struct device *dev, struct device_attribute *attr,
 {
 	struct cxl_memdev *cxlmd = to_cxl_memdev(dev);
 	struct cxl_dev_state *cxlds = cxlmd->cxlds;
-	unsigned long long len = cxl_pmem_size(cxlds);
+	unsigned long long len = cxl_part_size(cxlds, CXL_PARTMODE_PMEM);
 
 	return sysfs_emit(buf, "%#llx\n", len);
 }
@@ -426,10 +418,11 @@ static struct attribute *cxl_memdev_attributes[] = {
 	NULL,
 };
 
-static struct cxl_dpa_perf *to_pmem_perf(struct cxl_dev_state *cxlds)
+static struct cxl_dpa_perf *part_perf(struct cxl_dev_state *cxlds,
+				      enum cxl_partition_mode mode)
 {
 	for (int i = 0; i < cxlds->nr_partitions; i++)
-		if (cxlds->part[i].mode == CXL_PARTMODE_PMEM)
+		if (cxlds->part[i].mode == mode)
 			return &cxlds->part[i].perf;
 	return NULL;
 }
@@ -440,7 +433,7 @@ static ssize_t pmem_qos_class_show(struct device *dev,
 	struct cxl_memdev *cxlmd = to_cxl_memdev(dev);
 	struct cxl_dev_state *cxlds = cxlmd->cxlds;
 
-	return sysfs_emit(buf, "%d\n", to_pmem_perf(cxlds)->qos_class);
+	return sysfs_emit(buf, "%d\n", part_perf(cxlds, CXL_PARTMODE_PMEM)->qos_class);
 }
 
 static struct device_attribute dev_attr_pmem_qos_class =
@@ -452,20 +445,13 @@ static struct attribute *cxl_memdev_pmem_attributes[] = {
 	NULL,
 };
 
-static struct cxl_dpa_perf *to_ram_perf(struct cxl_dev_state *cxlds)
-{
-	if (cxlds->part[0].mode != CXL_PARTMODE_RAM)
-		return NULL;
-	return &cxlds->part[0].perf;
-}
-
 static ssize_t ram_qos_class_show(struct device *dev,
 				  struct device_attribute *attr, char *buf)
 {
 	struct cxl_memdev *cxlmd = to_cxl_memdev(dev);
 	struct cxl_dev_state *cxlds = cxlmd->cxlds;
 
-	return sysfs_emit(buf, "%d\n", to_ram_perf(cxlds)->qos_class);
+	return sysfs_emit(buf, "%d\n", part_perf(cxlds, CXL_PARTMODE_RAM)->qos_class);
 }
 
 static struct device_attribute dev_attr_ram_qos_class =
@@ -501,7 +487,7 @@ static umode_t cxl_ram_visible(struct kobject *kobj, struct attribute *a, int n)
 {
 	struct device *dev = kobj_to_dev(kobj);
 	struct cxl_memdev *cxlmd = to_cxl_memdev(dev);
-	struct cxl_dpa_perf *perf = to_ram_perf(cxlmd->cxlds);
+	struct cxl_dpa_perf *perf = part_perf(cxlmd->cxlds, CXL_PARTMODE_RAM);
 
 	if (a == &dev_attr_ram_qos_class.attr &&
 	    (!perf || perf->qos_class == CXL_QOS_CLASS_INVALID))
@@ -520,7 +506,7 @@ static umode_t cxl_pmem_visible(struct kobject *kobj, struct attribute *a, int n
 {
 	struct device *dev = kobj_to_dev(kobj);
 	struct cxl_memdev *cxlmd = to_cxl_memdev(dev);
-	struct cxl_dpa_perf *perf = to_pmem_perf(cxlmd->cxlds);
+	struct cxl_dpa_perf *perf = part_perf(cxlmd->cxlds, CXL_PARTMODE_PMEM);
 
 	if (a == &dev_attr_pmem_qos_class.attr &&
 	    (!perf || perf->qos_class == CXL_QOS_CLASS_INVALID))
diff --git a/drivers/cxl/cxlmem.h b/drivers/cxl/cxlmem.h
index 9106affd7c81..35268d1c387c 100644
--- a/drivers/cxl/cxlmem.h
+++ b/drivers/cxl/cxlmem.h
@@ -412,14 +412,11 @@ struct cxl_security_state {
 
 #define CXL_MAX_DC_PARTITIONS 8
 
-static inline resource_size_t cxl_pmem_size(struct cxl_dev_state *cxlds)
+static inline resource_size_t cxl_part_size(struct cxl_dev_state *cxlds,
+					    enum cxl_partition_mode mode)
 {
-	/*
-	 * Static PMEM may be at partition index 0 when there is no static RAM
-	 * capacity.
-	 */
 	for (int i = 0; i < cxlds->nr_partitions; i++)
-		if (cxlds->part[i].mode == CXL_PARTMODE_PMEM)
+		if (cxlds->part[i].mode == mode)
 			return resource_size(&cxlds->part[i].res);
 	return 0;
 }
diff --git a/drivers/cxl/mem.c b/drivers/cxl/mem.c
index 798e5c369cfc..9c4ef401cbad 100644
--- a/drivers/cxl/mem.c
+++ b/drivers/cxl/mem.c
@@ -139,7 +139,7 @@ static int cxl_mem_probe(struct device *dev)
 		return -ENXIO;
 	}
 
-	if (cxl_pmem_size(cxlds) && IS_ENABLED(CONFIG_CXL_PMEM)) {
+	if (cxl_part_size(cxlds, CXL_PARTMODE_PMEM) && IS_ENABLED(CONFIG_CXL_PMEM)) {
 		rc = devm_cxl_add_nvdimm(dev, parent_port, cxlmd);
 		if (rc) {
 			if (rc == -ENODEV)
diff --git a/include/cxl/cxl.h b/include/cxl/cxl.h
index 728decda57fd..1c04a7823f64 100644
--- a/include/cxl/cxl.h
+++ b/include/cxl/cxl.h
@@ -130,6 +130,26 @@ struct cxl_dpa_perf {
 	int qos_class;
 };
 
+/*
+ * Partitions share one flat DPA space in a fixed order:
+ *
+ *   DPA 0                                                     end
+ *   +---------------+---------------+---------------------------+
+ *   |      ram      |     pmem      |       dynamic_ram_1       |
+ *   +---------------+---------------+---------------------------+
+ *     part[0]         part[1]         part[2]
+ *
+ * The static ram and pmem partition order is mandated by CXL r4.0
+ * 8.2.10.9.2.1 "Get Partition Info" (opcode 4100h), Table 8-310: volatile
+ * capacity starts at DPA 0 and persistent capacity starts at the DPA
+ * immediately following it.  A dynamic partition has no such
+ * requirement -- 8.2.10.9.9.1 "Get Dynamic Capacity Configuration"
+ * (opcode 4800h), Table 8-347, only requires the DC Region Base to be
+ * 256MB aligned -- but Linux follows that precedent and requires it to
+ * start at the DPA immediately following static capacity: after pmem,
+ * after ram on a device with no pmem, or at DPA 0 on a device with no
+ * static capacity at all.  cxl_configure_dcd() enforces it.
+ */
 enum cxl_partition_mode {
 	CXL_PARTMODE_RAM,
 	CXL_PARTMODE_PMEM,
-- 
2.43.0