[PATCH v2] ACPI: OSL: Fix the memory mapping of an ACPI GAS that addresses a data structure

[james.liu@hpe.com]

From: James Liu <james.liu@hpe.com>

    Modify acpi_os_map_generic_address() & acpi_os_unmap_generic_address()
    to correctly handle cases that a GAS table (i.e., Table 5.1, ACPI 6.4)
    is used to address a data structure; in the case, the GAS has the field
    of "Register Bit Width" equal to 0.

    For example, "Injection Instruction Entry" (Table 18.25, ACPI 6.4) has
    a RegisterRegion field that is a GAS that points to a data structure
    SET_ERROR_TYPE_WITH_ADDRESS (Table 18.30), which is required when using
    EINJ (Error Injection module).

    This fix preserves a fairly sufficient memory space (i.e. page size) to
    store the data structure to prevent EINJ module from loading failure if
    platform firmware can correctly support Injection Instruction Entry in
    an EINJ table.

Signed-off-by: James Liu <james.liu@hpe.com>
---
 drivers/acpi/osl.c | 27 +++++++++++++++++++++++----
 1 file changed, 23 insertions(+), 4 deletions(-)

diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
index 45c5c0e45..99f987c8c 100644
--- a/drivers/acpi/osl.c
+++ b/drivers/acpi/osl.c
@@ -452,14 +452,20 @@ EXPORT_SYMBOL_GPL(acpi_os_unmap_memory);
 
 void __iomem *acpi_os_map_generic_address(struct acpi_generic_address *gas)
 {
-	u64 addr;
+	u64 addr = 0;
 
 	if (gas->space_id != ACPI_ADR_SPACE_SYSTEM_MEMORY)
 		return NULL;
 
+	/* Handle a case that GAS is used to address an ACPI data structure */
+	if (!gas->bit_width) {
+		pr_info("An ACPI data structure at 0x%llx is mapped\n", addr);
+		return  acpi_os_map_iomem(addr, PAGE_SIZE);
+	}
+
 	/* Handle possible alignment issues */
 	memcpy(&addr, &gas->address, sizeof(addr));
-	if (!addr || !gas->bit_width)
+	if (!addr)
 		return NULL;
 
 	return acpi_os_map_iomem(addr, gas->bit_width / 8);
@@ -468,15 +474,28 @@ EXPORT_SYMBOL(acpi_os_map_generic_address);
 
 void acpi_os_unmap_generic_address(struct acpi_generic_address *gas)
 {
-	u64 addr;
+	u64 addr = 0;
 	struct acpi_ioremap *map;
 
 	if (gas->space_id != ACPI_ADR_SPACE_SYSTEM_MEMORY)
 		return;
 
+	/* Handle a case that GAS is used to address an ACPI data structure */
+	if (!gas->bit_width) {
+		pr_info("An ACPI data structure at 0x%llx is unmapped\n", addr);
+		mutex_lock(&acpi_ioremap_lock);
+		map = acpi_map_lookup(addr, PAGE_SIZE);
+		if (!map) {
+			mutex_unlock(&acpi_ioremap_lock);
+			return;
+		}
+		acpi_os_drop_map_ref(map);
+		mutex_unlock(&acpi_ioremap_lock);
+	}
+
 	/* Handle possible alignment issues */
 	memcpy(&addr, &gas->address, sizeof(addr));
-	if (!addr || !gas->bit_width)
+	if (!addr)
 		return;
 
 	mutex_lock(&acpi_ioremap_lock);
-- 
2.25.1