From 30c66b528e1fc414be6f61121ec6263a379f308c Mon Sep 17 00:00:00 2001 From: Ashok Raj Date: Wed, 28 Feb 2018 11:28:41 +0100 Subject: [PATCH] x86/microcode/intel: Check microcode revision before updating sibling threads commit c182d2b7d0ca48e0d6ff16f7d883161238c447ed upstream. After updating microcode on one of the threads of a core, the other thread sibling automatically gets the update since the microcode resources on a hyperthreaded core are shared between the two threads. Check the microcode revision on the CPU before performing a microcode update and thus save us the WRMSR 0x79 because it is a particularly expensive operation. [ Borislav: Massage changelog and coding style. ] Signed-off-by: Ashok Raj Signed-off-by: Borislav Petkov Signed-off-by: Thomas Gleixner Tested-by: Tom Lendacky Tested-by: Ashok Raj Cc: Arjan Van De Ven Link: http://lkml.kernel.org/r/1519352533-15992-2-git-send-email-ashok.raj@intel.com Link: https://lkml.kernel.org/r/20180228102846.13447-3-bp@alien8.de [bwh: Backported to 4.4: - s/mc->/mc_intel->/ - Return 0 in this case - Adjust context] Signed-off-by: Ben Hutchings Signed-off-by: Greg Kroah-Hartman --- arch/x86/kernel/cpu/microcode/intel.c | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+) diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c index f3bc28f7ce39..0cef2b61f920 100644 --- a/arch/x86/kernel/cpu/microcode/intel.c +++ b/arch/x86/kernel/cpu/microcode/intel.c @@ -653,6 +653,17 @@ static int apply_microcode_early(struct ucode_cpu_info *uci, bool early) if (mc_intel == NULL) return 0; + /* + * Save us the MSR write below - which is a particular expensive + * operation - when the other hyperthread has updated the microcode + * already. + */ + rev = intel_get_microcode_revision(); + if (rev >= mc_intel->hdr.rev) { + uci->cpu_sig.rev = rev; + return 0; + } + /* write microcode via MSR 0x79 */ native_wrmsr(MSR_IA32_UCODE_WRITE, (unsigned long) mc_intel->bits, @@ -861,6 +872,18 @@ static int apply_microcode_intel(int cpu) if (get_matching_mc(mc_intel, cpu) == 0) return 0; + /* + * Save us the MSR write below - which is a particular expensive + * operation - when the other hyperthread has updated the microcode + * already. + */ + rev = intel_get_microcode_revision(); + if (rev >= mc_intel->hdr.rev) { + uci->cpu_sig.rev = rev; + c->microcode = rev; + return 0; + } + /* write microcode via MSR 0x79 */ wrmsr(MSR_IA32_UCODE_WRITE, (unsigned long) mc_intel->bits, -- 2.11.0