From patchwork Thu Sep 22 19:51:34 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Tony Luck X-Patchwork-Id: 12985752 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 7D2D9C6FA82 for ; Thu, 22 Sep 2022 19:51:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230079AbiIVTv6 (ORCPT ); Thu, 22 Sep 2022 15:51:58 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49102 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232312AbiIVTvs (ORCPT ); Thu, 22 Sep 2022 15:51:48 -0400 Received: from mga17.intel.com (mga17.intel.com [192.55.52.151]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1508E10C78E; Thu, 22 Sep 2022 12:51:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1663876307; x=1695412307; h=from:to:cc:subject:date:message-id:mime-version: content-transfer-encoding; bh=1Dio6FuAowFSRZXpVJEI0kJ8UFwvjWovjlQsBMPapkk=; b=DVsai5c1GpFcgrO2K9GFywrgT3u3exlF3Tw1Fv8w29M1TSHv73nmk1EF LmP5bAVZCw4HC562Y+yyIw8FRwfUV5uq1CzsvOs/It792ysFJeUY3fxO6 szdT5QEXU5aPgKskw3vMGEMMEfl94jbloJTRXmDWXOyjTkdPI7apZPZJE /ldw2R/BXfGWuBJ8acT85hMiOyaHP63eEFC+ahQnQLhHhP9I+YVMXignw T/ni1rNtWwikW92CXUNcLSzta2iUDIfd3gBSi0enufARHKHajQDKWZWrz h/dYMC6mrLPWT3jTbcNd2gf3Qi5jycjDIXEuAPi3ICPx/jI9bnxxrVEH5 Q==; X-IronPort-AV: E=McAfee;i="6500,9779,10478"; a="280783420" X-IronPort-AV: E=Sophos;i="5.93,337,1654585200"; d="scan'208";a="280783420" Received: from fmsmga007.fm.intel.com ([10.253.24.52]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Sep 2022 12:51:45 -0700 X-IronPort-AV: E=Sophos;i="5.93,337,1654585200"; d="scan'208";a="622246712" Received: from agluck-desk3.sc.intel.com ([172.25.222.78]) by fmsmga007-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Sep 2022 12:51:45 -0700 From: Tony Luck To: Borislav Petkov Cc: Yazen Ghannam , Smita Koralahalli , Carlos Bilbao , x86@kernel.org, linux-edac@vger.kernel.org, linux-kernel@vger.kernel.org, Tony Luck Subject: [PATCH 0/2] Dump stack after certain machine checks Date: Thu, 22 Sep 2022 12:51:34 -0700 Message-Id: <20220922195136.54575-1-tony.luck@intel.com> X-Mailer: git-send-email 2.37.3 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-edac@vger.kernel.org In general it isn't very useful to dump the kernel stack in the panic from a fatal machine check. The problem is almost always hardware related, so knowing how the kernel got to the routine that triggered the machine check isn't useful. But Linux now has the capability to recover from most user mode and a few kernel mode memory related machine checks. Validation folks are testing that out and occasionally bring a kernel log like this to me: [69608.047771] mce: [Hardware Error]: Machine check: Data load in unrecoverable area of kernel [69608.021729] mce: [Hardware Error]: TSC 7874eb580177 ADDR 43bb84bd00 MISC 86 PPIN 9f061818e1a92082 [69608.047773] Kernel panic - not syncing: Fatal local machine check [69608.021720] mce: [Hardware Error]: RIP 10: {copy_page+0x7/0x10} All I can tell them is that Linux was copying a page and hit poison in the source of the copy. But there are lots of reasons why Linux may be copying a page. A stack trace would help figure out if: 1) the test was bad and just injected an error into the wrong location 2) an injected error sat around in memory and was later consumed Case 2 will help identify places where Linux might use a "safe" copy function that returns an error to the caller which may attempt some sort of recovery. Patch 1 cleans up the Intel severity calculation by using a new severity table entry instead of some, now dubious, code to adjust the severity for errors in kernel context. Patch 2 adds a new severity level that triggers printing a stack trace. I've only updated the Intel severity calculation to use this new severity level. I'm not sure if AMD also has situations where this would be useful. If so, then mce_severity_amd() would need to be updated too to return different severity for IN_KERNEL and IN_KERNEL_RECOV cases. I've tested this out on systems that do both broadcast and local machine checks. Tony Luck (2): x86/mce: Use severity table to handle uncorrected errors in kernel x86/mce: Dump the stack for recoverable machine checks in kernel context arch/x86/kernel/cpu/mce/internal.h | 1 + arch/x86/kernel/cpu/mce/core.c | 11 +++++++++-- arch/x86/kernel/cpu/mce/severity.c | 10 ++++++---- 3 files changed, 16 insertions(+), 6 deletions(-) base-commit: 521a547ced6477c54b4b0cc206000406c221b4d6