From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f50.google.com (mail-wm0-f50.google.com [74.125.82.50]) by kanga.kvack.org (Postfix) with ESMTP id 28A586B002A for ; Thu, 31 Dec 2015 15:30:44 -0500 (EST) Received: by mail-wm0-f50.google.com with SMTP id f206so121717269wmf.0 for ; Thu, 31 Dec 2015 12:30:44 -0800 (PST) Received: from mail-wm0-x242.google.com (mail-wm0-x242.google.com. [2a00:1450:400c:c09::242]) by mx.google.com with ESMTPS id x16si39776716wme.57.2015.12.31.12.30.42 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 31 Dec 2015 12:30:42 -0800 (PST) Received: by mail-wm0-x242.google.com with SMTP id l65so42349661wmf.3 for ; Thu, 31 Dec 2015 12:30:42 -0800 (PST) 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> Date: Thu, 31 Dec 2015 12:30:42 -0800 Message-ID: Subject: Re: [PATCHV5 3/3] x86, ras: Add __mcsafe_copy() function to recover from machine checks From: Tony Luck Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: Andy Lutomirski 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" On Wed, Dec 30, 2015 at 3:32 PM, Tony Luck wrote: > Fifth is just a hack because I clearly didn't understand what I was > doing in parts 2&3 because my new class shows up as '3' not '1'! > > Andy: Can you explain the assembler/linker arithmetic for the class? Never mind ... figured it out. The fixup entry in the extable is: label - . + 0x2000000 - BIAS The "label - ." part evaluates to a smallish negative value (because the .fixup section is bundled in towards the end of .text, and the ex_table section comes right after. Then you add 0x20000000 to get a positive number, then *subtract* the BIAS. I'd picked BIAS = 0x40000000 thinking that would show up directly in class bits. But 0x1ffff000 - 0x40000000 is 0xdffff000 so bits 31 & 31 are both set, and this is class3 I switched to BIAS 0xC0000000 ... and now I get class 1 entries (bit31=0, bit30=1). New patch series coming soon. -Tony -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org