Commit-ID: 685ca6d797af9d41164dd64dd60145d4946fc152 Gitweb: http://git.kernel.org/tip/685ca6d797af9d41164dd64dd60145d4946fc152 Author: Borislav Petkov <[email protected]> AuthorDate: Wed, 20 Jun 2012 16:17:51 +0200 Committer: H. Peter Anvin <[email protected]> CommitDate: Wed, 22 Aug 2012 16:15:41 -0700
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 <[email protected]> Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: H. Peter Anvin <[email protected]> --- arch/x86/kernel/microcode_amd.c | 13 ++++++++++--- 1 files changed, 10 insertions(+), 3 deletions(-) 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 @@ 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); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
