x86, microcode, AMD: Check before applying a patch
Make sure we're actually applying a microcode patch to a core which
really needs it.
This brings only a very very very minor slowdown on F10:
0.032218828 sec vs 0.056010626 sec with this patch.
And small speedup on F15:
0.487089449 sec vs 0.180551162 sec (from perf output).
Also, fixup comments while at it.
Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>
Link: http://lkml.kernel.org/r/1344361461-10076-8-git-send-email-bp@amd64.org
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
diff --git a/arch/x86/kernel/microcode_amd.c b/arch/x86/kernel/microcode_amd.c
index 9421338..8fdf7d9 100644
--- a/arch/x86/kernel/microcode_amd.c
+++ b/arch/x86/kernel/microcode_amd.c
@@ -202,11 +202,18 @@
if (mc_amd == NULL)
return 0;
- wrmsrl(MSR_AMD64_PATCH_LOADER, (u64)(long)&mc_amd->hdr.data_code);
- /* get patch id after patching */
rdmsr(MSR_AMD64_PATCH_LEVEL, rev, dummy);
- /* check current patch id and patch's id for match */
+ /* need to apply patch? */
+ if (rev >= mc_amd->hdr.patch_id) {
+ c->microcode = rev;
+ return 0;
+ }
+
+ wrmsrl(MSR_AMD64_PATCH_LOADER, (u64)(long)&mc_amd->hdr.data_code);
+
+ /* verify patch application was successful */
+ rdmsr(MSR_AMD64_PATCH_LEVEL, rev, dummy);
if (rev != mc_amd->hdr.patch_id) {
pr_err("CPU%d: update failed for patch_level=0x%08x\n",
cpu, mc_amd->hdr.patch_id);