ACPI: APEI: EINJ: Discover EINJv2 parameters

The EINJv2 set_error_type_with_address structure has a flex array
to hold the component IDs and syndrome values used when injecting
multiple errors at once.

Discover the size of this array by taking the address from the
ACPI_EINJ_SET_ERROR_TYPE_WITH_ADDRESS entry in the EINJ table
and reading the BIOS copy of the structure.

Derive the maximum number of components from the length field
in the einjv2_extension_struct at the end of the BIOS copy.

Map the whole of the structure into kernel memory (and unmap
on module unload).

[Tony: Code unchanged from Zaid's original. New commit message]

Reviewed-by: Tony Luck <tony.luck@intel.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Zaid Alali <zaidal@os.amperecomputing.com>
Link: https://patch.msgid.link/20250617193026.637510-5-zaidal@os.amperecomputing.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Author: zaidal-ampere

drivers/acpi/apei/einj-core.c

@@ -108,6 +108,7 @@ static struct debugfs_blob_wrapper vendor_blob;
 static struct debugfs_blob_wrapper vendor_errors;
 static char vendor_dev[64];
 
+static u32 max_nr_components;
 static u32 available_error_type;
 static u32 available_error_type_v2;
 
@@ -178,6 +179,7 @@ static DEFINE_MUTEX(einj_mutex);
 bool einj_initialized __ro_after_init;
 
 static void __iomem *einj_param;
+static u32 v5param_size;
 
 static void einj_exec_ctx_init(struct apei_exec_context *ctx)
 {
@@ -302,11 +304,31 @@ static void __iomem *einj_get_parameter_address(void)
 		struct set_error_type_with_address v5param;
 		struct set_error_type_with_address __iomem *p;
 
+		v5param_size = sizeof(v5param);
 		p = acpi_os_map_iomem(pa_v5, sizeof(*p));
 		if (p) {
-			memcpy_fromio(&v5param, p, sizeof(v5param));
+			int offset, len;
+
+			memcpy_fromio(&v5param, p, v5param_size);
 			acpi5 = 1;
 			check_vendor_extension(pa_v5, &v5param);
+			if (available_error_type & ACPI65_EINJV2_SUPP) {
+				len = v5param.einjv2_struct.length;
+				offset = offsetof(struct einjv2_extension_struct, component_arr);
+				max_nr_components = (len - offset) /
+						sizeof(v5param.einjv2_struct.component_arr[0]);
+				/*
+				 * The first call to acpi_os_map_iomem above does not include the
+				 * component array, instead it is used to read and calculate maximum
+				 * number of components supported by the system. Below, the mapping
+				 * is expanded to include the component array.
+				 */
+				acpi_os_unmap_iomem(p, v5param_size);
+				offset = offsetof(struct set_error_type_with_address, einjv2_struct);
+				v5param_size = offset + struct_size(&v5param.einjv2_struct,
+					component_arr, max_nr_components);
+				p = acpi_os_map_iomem(pa_v5, v5param_size);
+			}
 			return p;
 		}
 	}
@@ -933,7 +955,7 @@ static void __exit einj_remove(struct faux_device *fdev)
 
 	if (einj_param) {
 		acpi_size size = (acpi5) ?
-			sizeof(struct set_error_type_with_address) :
+			v5param_size :
 			sizeof(struct einj_parameter);
 
 		acpi_os_unmap_iomem(einj_param, size);