From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756684AbbIUM1g (ORCPT ); Mon, 21 Sep 2015 08:27:36 -0400 Received: from mx1.redhat.com ([209.132.183.28]:45050 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756132AbbIUM1e (ORCPT ); Mon, 21 Sep 2015 08:27:34 -0400 Subject: Re: [PATCH v2 1/2] x86/msr: Carry on after a non-"safe" MSR access fails without !panic_on_oops To: Ingo Molnar , Andy Lutomirski References: <130a3b7ef4788baae3a6fe71293ab17442bc9a0a.1442793572.git.luto@kernel.org> <20150921084642.GA30984@gmail.com> Cc: Linus Torvalds , Thomas Gleixner , xen-devel , Arjan van de Ven , Andrew Morton , KVM list , the arch/x86 maintainers , Linux Kernel Mailing List , Peter Zijlstra From: Paolo Bonzini Message-ID: <55FFF7B3.5010608@redhat.com> Date: Mon, 21 Sep 2015 14:27:31 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.2.0 MIME-Version: 1.0 In-Reply-To: <20150921084642.GA30984@gmail.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 21/09/2015 10:46, Ingo Molnar wrote: > Or we could extend exception table entry encoding to include a 'warning bit', to > not bloat the kernel. If the exception handler code encounters such an exception > it would generate a one-time warning for that entry, but otherwise not crash the > kernel and continue execution with an all-zeroes result for the MSR read. The 'warning bit' already exists, it is the opcode that caused the fault. :) The concern about bloat is a good one. However, why is it necessary to keep native_*_msr* inline? If they are moved out-of-line, using the exception table becomes the obvious solution and doesn't cause bloat anymore. Paolo