Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933448AbbLONLo (ORCPT ); Tue, 15 Dec 2015 08:11:44 -0500 Received: from mail.skyhub.de ([78.46.96.112]:51244 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932176AbbLONLm (ORCPT ); Tue, 15 Dec 2015 08:11:42 -0500 Date: Tue, 15 Dec 2015 14:11:35 +0100 From: Borislav Petkov To: Tony Luck Cc: Ingo Molnar , Andrew Morton , Andy Lutomirski , Dan Williams , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-nvdimm@ml01.01.org, x86@kernel.org Subject: Re: [PATCHV2 3/3] x86, ras: Add mcsafe_memcpy() function to recover from machine checks Message-ID: <20151215131135.GE25973@pd.tnic> References: <23b2515da9d06b198044ad83ca0a15ba38c24e6e.1449861203.git.tony.luck@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <23b2515da9d06b198044ad83ca0a15ba38c24e6e.1449861203.git.tony.luck@intel.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1931 Lines: 47 On Thu, Dec 10, 2015 at 04:21:50PM -0800, Tony Luck wrote: > Using __copy_user_nocache() as inspiration create a memory copy > routine for use by kernel code with annotations to allow for > recovery from machine checks. > > Notes: > 1) Unlike the original we make no attempt to copy all the bytes > up to the faulting address. The original achieves that by > re-executing the failing part as a byte-by-byte copy, > which will take another page fault. We don't want to have > a second machine check! > 2) Likewise the return value for the original indicates exactly > how many bytes were not copied. Instead we provide the physical > address of the fault (thanks to help from do_machine_check() > 3) Provide helpful macros to decode the return value. > > Signed-off-by: Tony Luck > --- > arch/x86/include/asm/uaccess_64.h | 5 +++ > arch/x86/kernel/x8664_ksyms_64.c | 2 + > arch/x86/lib/copy_user_64.S | 91 +++++++++++++++++++++++++++++++++++++++ > 3 files changed, 98 insertions(+) ... > + * mcsafe_memcpy - Uncached memory copy with machine check exception handling > + * Note that we only catch machine checks when reading the source addresses. > + * Writes to target are posted and don't generate machine checks. > + * This will force destination/source out of cache for more performance. ... and the non-temporal version is the optimal one even though we're defaulting to copy_user_enhanced_fast_string for memcpy on modern Intel CPUs...? Btw, it should be also inside an ifdef if we're going to ifdef CONFIG_MCE_KERNEL_RECOVERY everywhere else. -- Regards/Gruss, Boris. ECO tip #101: Trim your mails when you reply. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/