acpi/ghes: move offset calculus to a separate function

Currently, CPER address location is calculated as an offset of
the hardware_errors table. It is also badly named, as the
offset actually used is the address where the CPER data starts,
and not the beginning of the error source.

Move the logic which calculates such offset to a separate
function, in preparation for a patch that will be changing the
logic to calculate it from the HEST table.

While here, properly name the variable which stores the cper
address.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Message-Id: <60fdd1bf379ba1db3099710868802aa49a27febb.1736945236.git.mchehab+huawei@kernel.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

hw/acpi/ghes.c

@@ -364,10 +364,37 @@ void acpi_ghes_add_fw_cfg(AcpiGhesState *ags, FWCfgState *s,
     ags->present = true;
 }
 
+static void get_hw_error_offsets(uint64_t ghes_addr,
+                                 uint64_t *cper_addr,
+                                 uint64_t *read_ack_register_addr)
+{
+    if (!ghes_addr) {
+        return;
+    }
+
+    /*
+     * non-HEST version supports only one source, so no need to change
+     * the start offset based on the source ID. Also, we can't validate
+     * the source ID, as it is stored inside the HEST table.
+     */
+
+    cpu_physical_memory_read(ghes_addr, cper_addr,
+                             sizeof(*cper_addr));
+
+    *cper_addr = le64_to_cpu(*cper_addr);
+
+    /*
+     * As the current version supports only one source, the ack offset is
+     * just sizeof(uint64_t).
+     */
+    *read_ack_register_addr = ghes_addr +
+                              ACPI_GHES_ERROR_SOURCE_COUNT * sizeof(uint64_t);
+}
+
 void ghes_record_cper_errors(const void *cper, size_t len,
                              uint16_t source_id, Error **errp)
 {
-    uint64_t error_block_addr, read_ack_register_addr, read_ack_register = 0;
+    uint64_t cper_addr = 0, read_ack_register_addr = 0, read_ack_register;
     uint64_t start_addr;
     AcpiGedState *acpi_ged_state;
     AcpiGhesState *ags;
@@ -389,18 +416,13 @@ void ghes_record_cper_errors(const void *cper, size_t len,
 
     start_addr += source_id * sizeof(uint64_t);
 
-    cpu_physical_memory_read(start_addr, &error_block_addr,
-                             sizeof(error_block_addr));
+    get_hw_error_offsets(start_addr, &cper_addr, &read_ack_register_addr);
 
-    error_block_addr = le64_to_cpu(error_block_addr);
-    if (!error_block_addr) {
+    if (!cper_addr) {
         error_setg(errp, "can not find Generic Error Status Block");
         return;
     }
 
-    read_ack_register_addr = start_addr +
-                             ACPI_GHES_ERROR_SOURCE_COUNT * sizeof(uint64_t);
-
     cpu_physical_memory_read(read_ack_register_addr,
                              &read_ack_register, sizeof(read_ack_register));
 
@@ -421,7 +443,7 @@ void ghes_record_cper_errors(const void *cper, size_t len,
                               &read_ack_register, sizeof(uint64_t));
 
     /* Write the generic error data entry into guest memory */
-    cpu_physical_memory_write(error_block_addr, cper, len);
+    cpu_physical_memory_write(cper_addr, cper, len);
 
     return;
 }