x86/microcode_amd: Add support for CPU family specific container files

We've decided to provide CPU family specific container files
(starting with CPU family 15h). E.g. for family 15h we have to
load microcode_amd_fam15h.bin instead of microcode_amd.bin

Rationale is that starting with family 15h patch size is larger
than 2KB which was hard coded as maximum patch size in various
microcode loaders (not just Linux).

Container files which include patches larger than 2KB cause
different kinds of trouble with such old patch loaders. Thus we
have to ensure that the default container file provides only
patches with size less than 2KB.
Signed-off-by: Andreas Herrmann <andreas.herrmann3@amd.com>
Cc: Borislav Petkov <borislav.petkov@amd.com>
Cc: <stable@kernel.org>
Link: http://lkml.kernel.org/r/20120120164412.GD24508@alberich.amd.com
[ documented the naming convention and tidied the code a bit. ]
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/microcode_amd.c

@@ -311,13 +311,33 @@ generic_load_microcode(int cpu, const u8 *data, size_t size)
 	return state;
 }
 
+/*
+ * AMD microcode firmware naming convention, up to family 15h they are in
+ * the legacy file:
+ *
+ *    amd-ucode/microcode_amd.bin
+ *
+ * This legacy file is always smaller than 2K in size.
+ *
+ * Starting at family 15h they are in family specific firmware files:
+ *
+ *    amd-ucode/microcode_amd_fam15h.bin
+ *    amd-ucode/microcode_amd_fam16h.bin
+ *    ...
+ *
+ * These might be larger than 2K.
+ */
 static enum ucode_state request_microcode_amd(int cpu, struct device *device)
 {
-	const char *fw_name = "amd-ucode/microcode_amd.bin";
+	char fw_name[36] = "amd-ucode/microcode_amd.bin";
 	const struct firmware *fw;
 	enum ucode_state ret = UCODE_NFOUND;
+	struct cpuinfo_x86 *c = &cpu_data(cpu);
+
+	if (c->x86 >= 0x15)
+		snprintf(fw_name, sizeof(fw_name), "amd-ucode/microcode_amd_fam%.2xh.bin", c->x86);
 
-	if (request_firmware(&fw, fw_name, device)) {
+	if (request_firmware(&fw, (const char *)fw_name, device)) {
 		pr_err("failed to load file %s\n", fw_name);
 		goto out;
 	}