Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 685ca6d7 authored by Borislav Petkov's avatar Borislav Petkov Committed by H. Peter Anvin
Browse files

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: default avatarBorislav Petkov <borislav.petkov@amd.com>
Link: http://lkml.kernel.org/r/1344361461-10076-8-git-send-email-bp@amd64.org


Signed-off-by: default avatarH. Peter Anvin <hpa@linux.intel.com>
parent e7e632f5

arch/x86/kernel/microcode_amd.c

+10 −3
Original line number Diff line number Diff line
@@ -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);