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x86, microcode, AMD: Check before applying a patch

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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>
This commit is contained in:
Borislav Petkov 2012-06-20 16:17:51 +02:00 committed by H. Peter Anvin
parent e7e632f5ba
commit 685ca6d797
1 changed files with 10 additions and 3 deletions
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13
arch/x86/kernel/microcode_amd.c
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@ -202,11 +202,18 @@ static int apply_microcode_amd(int cpu)
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);