diff --git a/drivers/acpi/apei/apei-base.c b/drivers/acpi/apei/apei-base.c
index e5d53b7ddc7e..1d3656f6919f 100644
--- a/drivers/acpi/apei/apei-base.c
+++ b/drivers/acpi/apei/apei-base.c
@@ -558,33 +558,48 @@ void apei_resources_release(struct apei_resources *resources)
 }
 EXPORT_SYMBOL_GPL(apei_resources_release);
 
-static int apei_check_gar(struct acpi_generic_address *reg, u64 *paddr)
+static int apei_check_gar(struct acpi_generic_address *reg, u64 *paddr,
+				u32 *access_bit_width)
 {
-	u32 width, space_id;
+	u32 bit_width, bit_offset, access_size_code, space_id;
 
-	width = reg->bit_width;
+	bit_width = reg->bit_width;
+	bit_offset = reg->bit_offset;
+	access_size_code = reg->access_width;
 	space_id = reg->space_id;
 	/* Handle possible alignment issues */
 	memcpy(paddr, &reg->address, sizeof(*paddr));
 	if (!*paddr) {
 		pr_warning(FW_BUG APEI_PFX
-			   "Invalid physical address in GAR [0x%llx/%u/%u]\n",
-			   *paddr, width, space_id);
+			   "Invalid physical address in GAR [0x%llx/%u/%u/%u/%u]\n",
+			   *paddr, bit_width, bit_offset, access_size_code,
+			   space_id);
 		return -EINVAL;
 	}
 
-	if ((width != 8) && (width != 16) && (width != 32) && (width != 64)) {
+	if (access_size_code < 1 || access_size_code > 4) {
 		pr_warning(FW_BUG APEI_PFX
-			   "Invalid bit width in GAR [0x%llx/%u/%u]\n",
-			   *paddr, width, space_id);
+			   "Invalid access size code in GAR [0x%llx/%u/%u/%u/%u]\n",
+			   *paddr, bit_width, bit_offset, access_size_code,
+			   space_id);
+		return -EINVAL;
+	}
+	*access_bit_width = 1UL << (access_size_code + 2);
+
+	if ((bit_width + bit_offset) > *access_bit_width) {
+		pr_warning(FW_BUG APEI_PFX
+			   "Invalid bit width + offset in GAR [0x%llx/%u/%u/%u/%u]\n",
+			   *paddr, bit_width, bit_offset, access_size_code,
+			   space_id);
 		return -EINVAL;
 	}
 
 	if (space_id != ACPI_ADR_SPACE_SYSTEM_MEMORY &&
 	    space_id != ACPI_ADR_SPACE_SYSTEM_IO) {
 		pr_warning(FW_BUG APEI_PFX
-			   "Invalid address space type in GAR [0x%llx/%u/%u]\n",
-			   *paddr, width, space_id);
+			   "Invalid address space type in GAR [0x%llx/%u/%u/%u/%u]\n",
+			   *paddr, bit_width, bit_offset, access_size_code,
+			   space_id);
 		return -EINVAL;
 	}
 
@@ -595,23 +610,25 @@ static int apei_check_gar(struct acpi_generic_address *reg, u64 *paddr)
 int apei_read(u64 *val, struct acpi_generic_address *reg)
 {
 	int rc;
+	u32 access_bit_width;
 	u64 address;
 	acpi_status status;
 
-	rc = apei_check_gar(reg, &address);
+	rc = apei_check_gar(reg, &address, &access_bit_width);
 	if (rc)
 		return rc;
 
 	*val = 0;
 	switch(reg->space_id) {
 	case ACPI_ADR_SPACE_SYSTEM_MEMORY:
-		status = acpi_os_read_memory64((acpi_physical_address)
-					     address, val, reg->bit_width);
+		status = acpi_os_read_memory64((acpi_physical_address) address,
+					       val, access_bit_width);
 		if (ACPI_FAILURE(status))
 			return -EIO;
 		break;
 	case ACPI_ADR_SPACE_SYSTEM_IO:
-		status = acpi_os_read_port(address, (u32 *)val, reg->bit_width);
+		status = acpi_os_read_port(address, (u32 *)val,
+					   access_bit_width);
 		if (ACPI_FAILURE(status))
 			return -EIO;
 		break;
@@ -627,22 +644,23 @@ EXPORT_SYMBOL_GPL(apei_read);
 int apei_write(u64 val, struct acpi_generic_address *reg)
 {
 	int rc;
+	u32 access_bit_width;
 	u64 address;
 	acpi_status status;
 
-	rc = apei_check_gar(reg, &address);
+	rc = apei_check_gar(reg, &address, &access_bit_width);
 	if (rc)
 		return rc;
 
 	switch (reg->space_id) {
 	case ACPI_ADR_SPACE_SYSTEM_MEMORY:
-		status = acpi_os_write_memory64((acpi_physical_address)
-					      address, val, reg->bit_width);
+		status = acpi_os_write_memory64((acpi_physical_address) address,
+						val, access_bit_width);
 		if (ACPI_FAILURE(status))
 			return -EIO;
 		break;
 	case ACPI_ADR_SPACE_SYSTEM_IO:
-		status = acpi_os_write_port(address, val, reg->bit_width);
+		status = acpi_os_write_port(address, val, access_bit_width);
 		if (ACPI_FAILURE(status))
 			return -EIO;
 		break;
@@ -661,23 +679,24 @@ static int collect_res_callback(struct apei_exec_context *ctx,
 	struct apei_resources *resources = data;
 	struct acpi_generic_address *reg = &entry->register_region;
 	u8 ins = entry->instruction;
+	u32 access_bit_width;
 	u64 paddr;
 	int rc;
 
 	if (!(ctx->ins_table[ins].flags & APEI_EXEC_INS_ACCESS_REGISTER))
 		return 0;
 
-	rc = apei_check_gar(reg, &paddr);
+	rc = apei_check_gar(reg, &paddr, &access_bit_width);
 	if (rc)
 		return rc;
 
 	switch (reg->space_id) {
 	case ACPI_ADR_SPACE_SYSTEM_MEMORY:
 		return apei_res_add(&resources->iomem, paddr,
-				    reg->bit_width / 8);
+				    access_bit_width / 8);
 	case ACPI_ADR_SPACE_SYSTEM_IO:
 		return apei_res_add(&resources->ioport, paddr,
-				    reg->bit_width / 8);
+				    access_bit_width / 8);
 	default:
 		return -EINVAL;
 	}