From dac6ca243c4c49a9ca7507d3d66140ebfac8b04b Mon Sep 17 00:00:00 2001 From: Borislav Petkov Date: Sun, 28 May 2017 22:04:14 +0200 Subject: [PATCH 1/3] x86/microcode/AMD: Change load_microcode_amd()'s param to bool to fix preemptibility bug With CONFIG_DEBUG_PREEMPT enabled, I get: BUG: using smp_processor_id() in preemptible [00000000] code: swapper/0/1 caller is debug_smp_processor_id CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.12.0-rc2+ #2 Call Trace: dump_stack check_preemption_disabled debug_smp_processor_id save_microcode_in_initrd_amd ? microcode_init save_microcode_in_initrd ... because, well, it says it above, we're using smp_processor_id() in preemptible code. But passing the CPU number is not really needed. It is only used to determine whether we're on the BSP, and, if so, to save the microcode patch for early loading. [ We don't absolutely need to do it on the BSP but we do that customarily there. ] Instead, convert that function parameter to a boolean which denotes whether the patch should be saved or not, thereby avoiding the use of smp_processor_id() in preemptible code. Signed-off-by: Borislav Petkov Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/20170528200414.31305-1-bp@alien8.de Signed-off-by: Ingo Molnar --- arch/x86/kernel/cpu/microcode/amd.c | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-) diff --git a/arch/x86/kernel/cpu/microcode/amd.c b/arch/x86/kernel/cpu/microcode/amd.c index 45db4d2ebd01..e9f4d762aa5b 100644 --- a/arch/x86/kernel/cpu/microcode/amd.c +++ b/arch/x86/kernel/cpu/microcode/amd.c @@ -320,7 +320,7 @@ void load_ucode_amd_ap(unsigned int cpuid_1_eax) } static enum ucode_state -load_microcode_amd(int cpu, u8 family, const u8 *data, size_t size); +load_microcode_amd(bool save, u8 family, const u8 *data, size_t size); int __init save_microcode_in_initrd_amd(unsigned int cpuid_1_eax) { @@ -338,8 +338,7 @@ int __init save_microcode_in_initrd_amd(unsigned int cpuid_1_eax) if (!desc.mc) return -EINVAL; - ret = load_microcode_amd(smp_processor_id(), x86_family(cpuid_1_eax), - desc.data, desc.size); + ret = load_microcode_amd(true, x86_family(cpuid_1_eax), desc.data, desc.size); if (ret != UCODE_OK) return -EINVAL; @@ -675,7 +674,7 @@ static enum ucode_state __load_microcode_amd(u8 family, const u8 *data, } static enum ucode_state -load_microcode_amd(int cpu, u8 family, const u8 *data, size_t size) +load_microcode_amd(bool save, u8 family, const u8 *data, size_t size) { enum ucode_state ret; @@ -689,8 +688,8 @@ load_microcode_amd(int cpu, u8 family, const u8 *data, size_t size) #ifdef CONFIG_X86_32 /* save BSP's matching patch for early load */ - if (cpu_data(cpu).cpu_index == boot_cpu_data.cpu_index) { - struct ucode_patch *p = find_patch(cpu); + if (save) { + struct ucode_patch *p = find_patch(0); if (p) { memset(amd_ucode_patch, 0, PATCH_MAX_SIZE); memcpy(amd_ucode_patch, p->data, min_t(u32, ksize(p->data), @@ -722,11 +721,12 @@ static enum ucode_state request_microcode_amd(int cpu, struct device *device, { char fw_name[36] = "amd-ucode/microcode_amd.bin"; struct cpuinfo_x86 *c = &cpu_data(cpu); + bool bsp = c->cpu_index == boot_cpu_data.cpu_index; enum ucode_state ret = UCODE_NFOUND; const struct firmware *fw; /* reload ucode container only on the boot cpu */ - if (!refresh_fw || c->cpu_index != boot_cpu_data.cpu_index) + if (!refresh_fw || !bsp) return UCODE_OK; if (c->x86 >= 0x15) @@ -743,7 +743,7 @@ static enum ucode_state request_microcode_amd(int cpu, struct device *device, goto fw_release; } - ret = load_microcode_amd(cpu, c->x86, fw->data, fw->size); + ret = load_microcode_amd(bsp, c->x86, fw->data, fw->size); fw_release: release_firmware(fw); From 5d9070b1f0fc9a159a9a3240c43004828408444b Mon Sep 17 00:00:00 2001 From: Borislav Petkov Date: Sun, 28 May 2017 11:03:42 +0200 Subject: [PATCH 2/3] x86/debug/32: Convert a smp_processor_id() call to raw to avoid DEBUG_PREEMPT warning ... to raw_smp_processor_id() to not trip the BUG: using smp_processor_id() in preemptible [00000000] code: swapper/0/1 check. The reasoning behind it is that __warn() already uses the raw_ variants but the show_regs() path on 32-bit doesn't. Signed-off-by: Borislav Petkov Cc: Josh Poimboeuf Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/20170528092212.fiod7kygpjm23m3o@pd.tnic Signed-off-by: Ingo Molnar --- arch/x86/kernel/process_32.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c index ff40e74c9181..ffeae818aa7a 100644 --- a/arch/x86/kernel/process_32.c +++ b/arch/x86/kernel/process_32.c @@ -78,7 +78,7 @@ void __show_regs(struct pt_regs *regs, int all) printk(KERN_DEFAULT "EIP: %pS\n", (void *)regs->ip); printk(KERN_DEFAULT "EFLAGS: %08lx CPU: %d\n", regs->flags, - smp_processor_id()); + raw_smp_processor_id()); printk(KERN_DEFAULT "EAX: %08lx EBX: %08lx ECX: %08lx EDX: %08lx\n", regs->ax, regs->bx, regs->cx, regs->dx); From c08d517480ea342cc43acdacc5cf4a795e18151d Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Thu, 1 Jun 2017 15:52:23 +0200 Subject: [PATCH 3/3] Revert "x86/PAT: Fix Xorg regression on CPUs that don't support PAT" This reverts commit cbed27cdf0e3f7ea3b2259e86b9e34df02be3fe4. As Andy Lutomirski observed: "I think this patch is bogus. pat_enabled() sure looks like it's supposed to return true if PAT is *enabled*, and these days PAT is 'enabled' even if there's no HW PAT support." Reported-by: Bernhard Held Reported-by: Chris Wilson Acked-by: Andy Lutomirski Cc: Andrew Morton Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Josh Poimboeuf Cc: Linus Torvalds Cc: Luis R. Rodriguez Cc: Mikulas Patocka Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Toshi Kani Cc: stable@vger.kernel.org # v4.2+ Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar --- arch/x86/mm/pat.c | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-) diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c index 83a59a67757a..9b78685b66e6 100644 --- a/arch/x86/mm/pat.c +++ b/arch/x86/mm/pat.c @@ -65,11 +65,9 @@ static int __init nopat(char *str) } early_param("nopat", nopat); -static bool __read_mostly __pat_initialized = false; - bool pat_enabled(void) { - return __pat_initialized; + return !!__pat_enabled; } EXPORT_SYMBOL_GPL(pat_enabled); @@ -227,14 +225,13 @@ static void pat_bsp_init(u64 pat) } wrmsrl(MSR_IA32_CR_PAT, pat); - __pat_initialized = true; __init_cache_modes(pat); } static void pat_ap_init(u64 pat) { - if (!this_cpu_has(X86_FEATURE_PAT)) { + if (!boot_cpu_has(X86_FEATURE_PAT)) { /* * If this happens we are on a secondary CPU, but switched to * PAT on the boot CPU. We have no way to undo PAT. @@ -309,7 +306,7 @@ void pat_init(void) u64 pat; struct cpuinfo_x86 *c = &boot_cpu_data; - if (!__pat_enabled) { + if (!pat_enabled()) { init_cache_modes(); return; }