[RFC PATCH v2 3/5] acpi/hmat: Add helper functions to provide extended linear cache translation

[Dave Jiang <dave.jiang@intel.com>]

Add helper functions to help do address translation for either the address
of the extended linear cache or its alias address. The translation function
attempt to detect an I/O hole in the proximity domain and adjusts the
address if the hole impacts the aliasing of the address. The range of the
I/O hole is retrieved by walking through the associated memory target
resources.

Signed-off-by: Dave Jiang <dave.jiang@intel.com>
---
v2:
- Drop extra variable and use 'res' from the loop. (Jonathan)
- Break up multiple if statements into single blocks and add comments. (Jonathan)
---
 drivers/acpi/numa/hmat.c | 148 +++++++++++++++++++++++++++++++++++++++
 include/linux/acpi.h     |  14 ++++
 2 files changed, 162 insertions(+)

diff --git a/drivers/acpi/numa/hmat.c b/drivers/acpi/numa/hmat.c
index 92b818b72ecc..6c686d3c7266 100644
--- a/drivers/acpi/numa/hmat.c
+++ b/drivers/acpi/numa/hmat.c
@@ -152,6 +152,154 @@ int hmat_get_extended_linear_cache_size(struct resource *backing_res, int nid,
 }
 EXPORT_SYMBOL_NS_GPL(hmat_get_extended_linear_cache_size, CXL);
 
+static int alias_address_find_iohole(struct memory_target *target,
+				     u64 address, u64 alias, struct range *hole)
+{
+	struct resource *res, *prev;
+
+	*hole = (struct range) {
+		.start = 0,
+		.end = -1,
+	};
+
+	/* First find the resource that the address is in */
+	prev = target->memregions.child;
+	for (res = target->memregions.child; res; res = res->sibling) {
+		if (alias >= res->start && alias <= res->end)
+			break;
+		prev = res;
+	}
+	if (!res)
+		return -EINVAL;
+
+	/* No memory hole */
+	if (res == prev)
+		return 0;
+
+	/* If address is within the current resource, no need to deal with memory hole */
+	if (address >= res->start)
+		return 0;
+
+	*hole = (struct range) {
+		.start = prev->end + 1,
+		.end = res->start - 1,
+	};
+
+	return 0;
+}
+
+int hmat_extended_linear_cache_alias_xlat(u64 address, u64 *alias, int nid)
+{
+	unsigned int pxm = node_to_pxm(nid);
+	struct memory_target *target;
+	struct range iohole;
+	int rc;
+
+	target = find_mem_target(pxm);
+	if (!target)
+		return -EINVAL;
+
+	rc = alias_address_find_iohole(target, address, *alias, &iohole);
+	if (rc)
+		return rc;
+
+	if (!range_len(&iohole))
+		return 0;
+
+	/*
+	 * If the cache start (address) is behind the MMIO I/O hole then there
+	 * is no change to the passed in CXL address (alias).
+	 */
+	if (address >= iohole.start)
+		return 0;
+
+	/*
+	 * If the aliased CXL address is before the MMIO I/O hole start then
+	 * CXL address (alias) is also not impacted.
+	 */
+	if (*alias <= iohole.start)
+		return 0;
+
+	*alias += range_len(&iohole);
+
+	return 0;
+}
+EXPORT_SYMBOL_NS_GPL(hmat_extended_linear_cache_alias_xlat, CXL);
+
+static int target_address_find_iohole(struct memory_target *target,
+				      u64 address, u64 alias,
+				      struct range *hole)
+{
+	struct resource *res, *next;
+
+	*hole = (struct range) {
+		.start = 0,
+		.end = -1,
+	};
+
+	/* First find the resource that the address is in */
+	for (res = target->memregions.child; res; res = res->sibling) {
+		if (address >= res->start && address <= res->end)
+			break;
+	}
+	if (!res)
+		return -EINVAL;
+
+	next = res->sibling;
+	/* No memory hole after the region */
+	if (!next)
+		return 0;
+
+	/* If alias is within the current resource, no need to deal with memory hole */
+	if (alias <= res->end)
+		return 0;
+
+	*hole = (struct range) {
+		.start = res->end + 1,
+		.end = next->start - 1,
+	};
+
+	return 0;
+}
+
+int hmat_extended_linear_cache_address_xlat(u64 *address, u64 alias, int nid)
+{
+	unsigned int pxm = node_to_pxm(nid);
+	struct memory_target *target;
+	struct range iohole;
+	int rc;
+
+	target = find_mem_target(pxm);
+	if (!target)
+		return -EINVAL;
+
+	rc = target_address_find_iohole(target, *address, alias, &iohole);
+	if (rc)
+		return rc;
+
+	if (!range_len(&iohole))
+		return 0;
+
+	 /*
+	  * If the CXL address is before the MMIO hole then there is no change
+	  * to the passed in cache address.
+	  */
+	if (alias <= iohole.end)
+		return 0;
+
+	/*
+	 * If the calculated cache address is after the MMIO hole then there
+	 * is no change to the passed in cache address.
+	 */
+	if (*address >= iohole.end)
+		return 0;
+
+	*address -= range_len(&iohole);
+
+	return 0;
+}
+EXPORT_SYMBOL_NS_GPL(hmat_extended_linear_cache_address_xlat, CXL);
+
 static struct memory_target *acpi_find_genport_target(u32 uid)
 {
 	struct memory_target *target;
diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index 10ffba7cb9ad..18a94d382d40 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -438,6 +438,8 @@ int thermal_acpi_critical_trip_temp(struct acpi_device *adev, int *ret_temp);
 int acpi_get_genport_coordinates(u32 uid, struct access_coordinate *coord);
 int hmat_get_extended_linear_cache_size(struct resource *backing_res, int nid,
 					resource_size_t *size);
+int hmat_extended_linear_cache_alias_xlat(u64 address, u64 *alias, int nid);
+int hmat_extended_linear_cache_address_xlat(u64 *address, u64 alias, int nid);
 #else
 static inline int acpi_get_genport_coordinates(u32 uid,
 					       struct access_coordinate *coord)
@@ -450,6 +452,18 @@ static inline int hmat_get_extended_linear_cache_size(struct resource *backing_r
 {
 	return -EOPNOTSUPP;
 }
+
+static inline int hmat_extended_linear_cache_alias_xlat(u64 address,
+							u64 *alias, int nid)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline int hmat_extended_linear_cache_address_xlat(u64 *address,
+							  u64 alias, int nid)
+{
+	return -EOPNOTSUPP;
+}
 #endif
 
 #ifdef CONFIG_ACPI_NUMA
-- 
2.47.0