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From:   james.liu@hpe.com
To:     rafael@kernel.org, lenb@kernel.org
Cc:     linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org,
        rwright@hpe.com, david.chang@hpe.co, clayc@hpe.com,
        james.liu@hpe.com
Subject: [PATCH]     ACPI: OSL: Fix the memory mapping of an ACPI GAS that addresses a data structure
Date:   Fri,  1 Apr 2022 17:28:40 +0000
Message-Id: <20220401172840.1252-1-james.liu@hpe.com>
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From: James Liu <james.liu@hpe.com>

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

    For example, "Injection Instruction Entry" (Table 18.25 in 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 so as to prevent EINJ module from loading
    failure if platform firmware can support Injection Instruction Entry in
    an EINJ table.

Signed-off-by: James Liu <james.liu@hpe.com>
---
 drivers/acpi/osl.c | 23 +++++++++++++++++++++--
 1 file changed, 21 insertions(+), 2 deletions(-)

diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
index 45c5c0e45..ab2f584b1 100644
--- a/drivers/acpi/osl.c
+++ b/drivers/acpi/osl.c
@@ -457,9 +457,15 @@ void __iomem *acpi_os_map_generic_address(struct acpi_generic_address *gas)
 	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);
@@ -474,9 +480,22 @@ void acpi_os_unmap_generic_address(struct acpi_generic_address *gas)
 	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