Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754537AbbL0CRY (ORCPT ); Sat, 26 Dec 2015 21:17:24 -0500 Received: from mail-oi0-f47.google.com ([209.85.218.47]:35815 "EHLO mail-oi0-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754499AbbL0CRU (ORCPT ); Sat, 26 Dec 2015 21:17:20 -0500 MIME-Version: 1.0 In-Reply-To: References: <20151224214632.GF4128@pd.tnic> <20151225114937.GA862@pd.tnic> <5FBC1CF1-095B-466D-85D6-832FBFA98364@intel.com> <20151226103252.GA21988@pd.tnic> From: Andy Lutomirski Date: Sat, 26 Dec 2015 18:16:59 -0800 Message-ID: Subject: Re: [PATCHV5 3/3] x86, ras: Add __mcsafe_copy() function to recover from machine checks To: Tony Luck Cc: Borislav Petkov , linux-nvdimm , X86 ML , "elliott@hpe.com" , "linux-mm@kvack.org" , Andrew Morton , "Williams, Dan J" , Ingo Molnar , "linux-kernel@vger.kernel.org" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1553 Lines: 33 On Sat, Dec 26, 2015 at 6:15 PM, Andy Lutomirski wrote: > On Sat, Dec 26, 2015 at 6:08 PM, Tony Luck wrote: >> On Sat, Dec 26, 2015 at 6:54 AM, Andy Lutomirski wrote: >>> On Dec 26, 2015 6:33 PM, "Borislav Petkov" wrote: >>>> Andy, why is that? It makes the exception handling much simpler this way... >>>> >>> >>> I like the idea of moving more logic into C, but I don't like >>> splitting the logic across files and adding nasty special cases like >>> this. >>> >>> But what if we generalized it? An extable entry gives a fault IP and >>> a landing pad IP. Surely we can squeeze a flag bit in there. >> >> The clever squeezers have already been here. Instead of a pair >> of 64-bit values for fault_ip and fixup_ip they managed with a pair >> of 32-bit values that are each the relative offset of the desired address >> from the table location itself. >> >> We could make one of them 31-bits (since even an "allyesconfig" kernel >> is still much smaller than a gigabyte) to free a bit for a flag. But there >> are those external tools to pre-sort exception tables that would all >> need to be fixed too. Wait, why? The external tools sort by source address, and we'd squeeze the flag into the target address, no? --Andy -- 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/