ACPI, APEI, Resolve false conflict between ACPI NVS and APEI

Some firmware will access memory in ACPI NVS region via APEI. That
is, instructions in APEI ERST/EINJ table will read/write ACPI NVS
region. The original resource conflict checking in APEI code will
check memory/ioport accessed by APEI via general resource management
mech. But ACPI NVS region is marked as busy already, so that the
false resource conflict will prevent APEI ERST/EINJ to work.

To fix this, this patch excludes ACPI NVS regions when APEI components
request resources. So that they will not conflict with ACPI NVS
regions.

Reported-and-tested-by: Pavel Ivanov <[e-mail]>
Signed-off-by: Huang Ying <[e-mail]>
Signed-off-by: Len Brown <[e-mail]>

drivers/acpi/apei/apei-base.c

···
 }
 EXPORT_SYMBOL_GPL(apei_resources_sub);
 
+static int apei_get_nvs_callback(__u64 start, __u64 size, void *data)
+{
+	struct apei_resources *resources = data;
+	return apei_res_add(&resources->iomem, start, size);
+}
+
+static int apei_get_nvs_resources(struct apei_resources *resources)
+{
+	return acpi_nvs_for_each_region(apei_get_nvs_callback, resources);
+}
+
 /*
- * IO memory/port rersource management mechanism is used to check
+ * IO memory/port resource management mechanism is used to check
  * whether memory/port area used by GARs conflicts with normal memory
  * or IO memory/port of devices.
  */
···
 {
 	struct apei_res *res, *res_bak = NULL;
 	struct resource *r;
+	struct apei_resources nvs_resources;
 	int rc;
 
 	rc = apei_resources_sub(resources, &apei_resources_all);
 	if (rc)
 		return rc;
+
+	/*
+	 * Some firmware uses ACPI NVS region, that has been marked as
+	 * busy, so exclude it from APEI resources to avoid false
+	 * conflict.
+	 */
+	apei_resources_init(&nvs_resources);
+	rc = apei_get_nvs_resources(&nvs_resources);
+	if (rc)
+		goto res_fini;
+	rc = apei_resources_sub(resources, &nvs_resources);
+	if (rc)
+		goto res_fini;
 
 	rc = -EINVAL;
 	list_for_each_entry(res, &resources->iomem, list) {
···
 			break;
 		release_mem_region(res->start, res->end - res->start);
 	}
+res_fini:
+	apei_resources_fini(&nvs_resources);
 	return rc;
 }
 EXPORT_SYMBOL_GPL(apei_resources_request);