This is a note to let you know that I've just added the patch titled

x86/microcode/intel: Check microcode revision before updating sibling threads

to the 4.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: x86-microcode-intel-check-microcode-revision-before-updating-sibling-threads.patch and it can be found in the queue-4.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From c182d2b7d0ca48e0d6ff16f7d883161238c447ed Mon Sep 17 00:00:00 2001

From: Ashok Raj ashok.raj@intel.com Date: Wed, 28 Feb 2018 11:28:41 +0100 Subject: x86/microcode/intel: Check microcode revision before updating sibling threads

From: Ashok Raj ashok.raj@intel.com

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 ashok.raj@intel.com Signed-off-by: Borislav Petkov bp@suse.de Signed-off-by: Thomas Gleixner tglx@linutronix.de Tested-by: Tom Lendacky thomas.lendacky@amd.com Tested-by: Ashok Raj ashok.raj@intel.com Cc: Arjan Van De Ven arjan.van.de.ven@intel.com Link: http://lkml.kernel.org/r/1519352533-15992-2-git-send-email-ashok.raj@intel.c... Link: https://lkml.kernel.org/r/20180228102846.13447-3-bp@alien8.de Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- arch/x86/kernel/cpu/microcode/intel.c | 27 ++++++++++++++++++++++++--- 1 file changed, 24 insertions(+), 3 deletions(-)

--- a/arch/x86/kernel/cpu/microcode/intel.c +++ b/arch/x86/kernel/cpu/microcode/intel.c @@ -589,6 +589,17 @@ static int apply_microcode_early(struct if (!mc) 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->hdr.rev) { + uci->cpu_sig.rev = rev; + return UCODE_OK; + } + /* write microcode via MSR 0x79 */ native_wrmsrl(MSR_IA32_UCODE_WRITE, (unsigned long)mc->bits);

@@ -776,7 +787,7 @@ static enum ucode_state apply_microcode_ { struct microcode_intel *mc; struct ucode_cpu_info *uci; - struct cpuinfo_x86 *c; + struct cpuinfo_x86 *c = &cpu_data(cpu); static int prev_rev; u32 rev;

@@ -793,6 +804,18 @@ static enum ucode_state apply_microcode_ return UCODE_NFOUND; }

+ /* + * 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->hdr.rev) { + uci->cpu_sig.rev = rev; + c->microcode = rev; + return UCODE_OK; + } + /* write microcode via MSR 0x79 */ wrmsrl(MSR_IA32_UCODE_WRITE, (unsigned long)mc->bits);

@@ -813,8 +836,6 @@ static enum ucode_state apply_microcode_ prev_rev = rev; }

- c = &cpu_data(cpu); - uci->cpu_sig.rev = rev; c->microcode = rev;

Patches currently in stable-queue which might be from ashok.raj@intel.com are

queue-4.15/x86-microcode-intel-check-microcode-revision-before-updating-sibling-threads.patch queue-4.15/x86-microcode-attempt-late-loading-only-when-new-microcode-is-present.patch queue-4.15/x86-microcode-propagate-return-value-from-updating-functions.patch queue-4.15/x86-cpu-check-cpu-feature-bits-after-microcode-upgrade.patch queue-4.15/x86-microcode-intel-writeback-and-invalidate-caches-before-updating-microcode.patch queue-4.15/x86-microcode-intel-look-into-the-patch-cache-first.patch queue-4.15/x86-microcode-request-microcode-on-the-bsp.patch queue-4.15/x86-microcode-get-rid-of-struct-apply_microcode_ctx.patch queue-4.15/x86-microcode-fix-cpu-synchronization-routine.patch queue-4.15/x86-microcode-synchronize-late-microcode-loading.patch queue-4.15/x86-microcode-do-not-upload-microcode-if-cpus-are-offline.patch queue-4.15/x86-cpu-add-a-microcode-loader-callback.patch