From c26665ab5c49ad3e142e0f054ca3204f259ba09c Mon Sep 17 00:00:00 2001 From: Borislav Petkov Date: Fri, 20 Jan 2017 21:29:40 +0100 Subject: [PATCH] x86/microcode/intel: Drop stashed AP patch pointer optimization This was meant to save us the scanning of the microcode containter in the initrd since the first AP had already done that but it can also hurt us: Imagine a single hyperthreaded CPU (Intel(R) Atom(TM) CPU N270, for example) which updates the microcode on the BSP but since the microcode engine is shared between the two threads, the update on CPU1 doesn't happen because it has already happened on CPU0 and we don't find a newer microcode revision on CPU1. Which doesn't set the intel_ucode_patch pointer and at initrd jettisoning time we don't save the microcode patch for later application. Now, when we suspend to RAM, the loaded microcode gets cleared so we need to reload but there's no patch saved in the cache. Removing the optimization fixes this issue and all is fine and dandy. Fixes: 06b8534cb728 ("x86/microcode: Rework microcode loading") Signed-off-by: Borislav Petkov Reviewed-by: Thomas Gleixner Link: http://lkml.kernel.org/r/20170120202955.4091-2-bp@alien8.de Signed-off-by: Thomas Gleixner --- arch/x86/kernel/cpu/microcode/intel.c | 9 +-------- 1 file changed, 1 insertion(+), 8 deletions(-) diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c index 3f329b74e040..8325d8a09ab0 100644 --- a/arch/x86/kernel/cpu/microcode/intel.c +++ b/arch/x86/kernel/cpu/microcode/intel.c @@ -41,7 +41,7 @@ static const char ucode_path[] = "kernel/x86/microcode/GenuineIntel.bin"; -/* Current microcode patch used in early patching */ +/* Current microcode patch used in early patching on the APs. */ struct microcode_intel *intel_ucode_patch; static inline bool cpu_signatures_match(unsigned int s1, unsigned int p1, @@ -607,12 +607,6 @@ int __init save_microcode_in_initrd_intel(void) struct ucode_cpu_info uci; struct cpio_data cp; - /* - * AP loading didn't find any microcode patch, no need to save anything. - */ - if (!intel_ucode_patch || IS_ERR(intel_ucode_patch)) - return 0; - if (!load_builtin_intel_microcode(&cp)) cp = find_microcode_in_initrd(ucode_path, false); @@ -628,7 +622,6 @@ int __init save_microcode_in_initrd_intel(void) return 0; } - /* * @res_patch, output: a pointer to the patch we found. */ -- 2.20.1