From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9DFECC001DC for ; Mon, 17 Jul 2023 15:24:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231288AbjGQPYO (ORCPT ); Mon, 17 Jul 2023 11:24:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56794 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231403AbjGQPYG (ORCPT ); Mon, 17 Jul 2023 11:24:06 -0400 Received: from lobo.ruivo.org (lobo.ruivo.org [173.14.175.98]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 736BB199 for ; Mon, 17 Jul 2023 08:23:49 -0700 (PDT) Received: by lobo.ruivo.org (Postfix, from userid 1011) id DEC3752E14; Mon, 17 Jul 2023 11:23:35 -0400 (EDT) Received: from jake.ruivo.org (bob.qemu.ruivo [192.168.72.19]) by lobo.ruivo.org (Postfix) with ESMTPA id A4E2B52998; Mon, 17 Jul 2023 11:23:17 -0400 (EDT) Received: by jake.ruivo.org (Postfix, from userid 1000) id 930E622007F; Mon, 17 Jul 2023 11:23:17 -0400 (EDT) Date: Mon, 17 Jul 2023 11:23:17 -0400 From: Aristeu Rozanski To: Tony Luck Cc: "linux-edac@vger.kernel.org" , Borislav Petkov , "aris@redhat.com" Subject: [PATCH v4] mce: prevent concurrent polling of MCE events Message-ID: <20230717152317.GA94963@cathedrallabs.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/2.2.9 (2022-11-12) Precedence: bulk List-ID: X-Mailing-List: linux-edac@vger.kernel.org On Intel microarchitectures that support CMCI but have it disabled (BIOS, kernel option or CMCI storm code) the kernel will resort to polling for MCEs. In these microarchitectures the IMC registers are shared by all CPUs in the same package and despite the fact that the polling is set up in the kernel to prevent all CPUs to poll at the same time, it's still possible they'll overlap and report the same MCE multiple times. This patch fixes this by introducing synchronization during polling only for the affected microarchitectures. v4: get rid of unneeded variable on intel_cmci_poll_unlock() and simplify unserialize_mc_bank_access() v3: add {,un}serialize_mc_bank_access() as intermediate functions as requested by Tony Luck Signed-off-by: Aristeu Rozanski Reviewed-by: Tony Luck Cc: Tony Luck Cc: Aristeu Rozanski Cc: Borislav Petkov Cc: linux-edac@vger.kernel.org --- arch/x86/kernel/cpu/mce/core.c | 18 +++++++++++++++ arch/x86/kernel/cpu/mce/intel.c | 44 +++++++++++++++++++++++++++++++------ arch/x86/kernel/cpu/mce/internal.h | 4 +++ 3 files changed, 59 insertions(+), 7 deletions(-) --- linus-2.6.orig/arch/x86/kernel/cpu/mce/core.c 2023-06-26 12:37:12.972386600 -0400 +++ linus-2.6/arch/x86/kernel/cpu/mce/core.c 2023-06-27 15:09:11.812208744 -0400 @@ -1578,6 +1578,22 @@ return 0; } #endif +static bool serialize_mc_bank_access(void) +{ + if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL) + return false; + + return intel_cmci_poll_lock(); +} + +static void unserialize_mc_bank_access(bool locked) +{ + if (!locked) + return; + + intel_cmci_poll_unlock(); +} + /* * Periodic polling timer for "silent" machine check errors. If the * poller finds an MCE, poll 2x faster. When the poller finds no more @@ -1618,7 +1634,9 @@ static void mce_timer_fn(struct timer_li iv = __this_cpu_read(mce_next_interval); if (mce_available(this_cpu_ptr(&cpu_info))) { + bool locked = serialize_mc_bank_access(); machine_check_poll(0, this_cpu_ptr(&mce_poll_banks)); + unserialize_mc_bank_access(locked); if (mce_intel_cmci_poll()) { iv = mce_adjust_timer(iv); --- linus-2.6.orig/arch/x86/kernel/cpu/mce/intel.c 2023-06-26 12:37:12.972386600 -0400 +++ linus-2.6/arch/x86/kernel/cpu/mce/intel.c 2023-06-27 15:09:31.672032470 -0400 @@ -73,13 +73,8 @@ enum { static atomic_t cmci_storm_on_cpus; -static int cmci_supported(int *banks) +static bool cmci_supported_hw(void) { - u64 cap; - - if (mca_cfg.cmci_disabled || mca_cfg.ignore_ce) - return 0; - /* * Vendor check is not strictly needed, but the initial * initialization is vendor keyed and this @@ -87,10 +82,24 @@ return 0; */ if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL && boot_cpu_data.x86_vendor != X86_VENDOR_ZHAOXIN) - return 0; + return false; if (!boot_cpu_has(X86_FEATURE_APIC) || lapic_get_maxlvt() < 6) + return false; + + return true; +} + +static int cmci_supported(int *banks) +{ + u64 cap; + + if (mca_cfg.cmci_disabled || mca_cfg.ignore_ce) + return 0; + + if (!cmci_supported_hw()) return 0; + rdmsrl(MSR_IA32_MCG_CAP, cap); *banks = min_t(unsigned, MAX_NR_BANKS, cap & 0xff); return !!(cap & MCG_CMCI_P); @@ -519,3 +528,24 @@ ((m->status & 0xa0000000ffffffff) == 0x8 return false; } + +/* + * On systems that do support CMCI but it's disabled, polling for MCEs can + * cause the same event to be reported multiple times because IA32_MCi_STATUS + * is shared by the same package. + */ +static DEFINE_SPINLOCK(cmci_poll_lock); +bool intel_cmci_poll_lock(void) +{ + if (!cmci_supported_hw()) + return false; + + spin_lock(&cmci_poll_lock); + + return true; +} + +void intel_cmci_poll_unlock(void) +{ + spin_unlock(&cmci_poll_lock); +} --- linus-2.6.orig/arch/x86/kernel/cpu/mce/internal.h 2023-06-26 12:37:12.972386600 -0400 +++ linus-2.6/arch/x86/kernel/cpu/mce/internal.h 2023-06-27 15:09:53.180841560 -0400 @@ -49,6 +49,8 @@ void intel_init_cmci(void); void intel_init_lmce(void); void intel_clear_lmce(void); bool intel_filter_mce(struct mce *m); +bool intel_cmci_poll_lock(void); +void intel_cmci_poll_unlock(void); #else # define cmci_intel_adjust_timer mce_adjust_timer_default static inline bool mce_intel_cmci_poll(void) { return false; } @@ -58,6 +60,8 @@ static inline void intel_init_cmci(void) static inline void intel_init_lmce(void) { } static inline void intel_clear_lmce(void) { } static inline bool intel_filter_mce(struct mce *m) { return false; } +static inline bool intel_cmci_poll_lock(void) { return false; } +static inline void intel_cmci_poll_unlock(void) { } #endif void mce_timer_kick(unsigned long interval); -- Aristeu