From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755344AbaGIOce (ORCPT ); Wed, 9 Jul 2014 10:32:34 -0400 Received: from mga11.intel.com ([192.55.52.93]:32888 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755177AbaGIOcc convert rfc822-to-8bit (ORCPT ); Wed, 9 Jul 2014 10:32:32 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.01,631,1400050800"; d="scan'208";a="567385464" From: "Liang, Kan" To: Peter Zijlstra CC: "andi@firstfloor.org" , "linux-kernel@vger.kernel.org" , "kvm@vger.kernel.org" Subject: RE: [PATCH V4 1/2] perf ignore LBR and extra_regs. Thread-Topic: [PATCH V4 1/2] perf ignore LBR and extra_regs. Thread-Index: AQHPmw42PYiPusxucki+Ie3j6NurFZuXRIqAgACHbiA= Date: Wed, 9 Jul 2014 14:32:28 +0000 Message-ID: <37D7C6CF3E00A74B8858931C1DB2F077014D2005@SHSMSX103.ccr.corp.intel.com> References: <1404838181-3911-1-git-send-email-kan.liang@intel.com> <20140709141631.GE9918@twins.programming.kicks-ass.net> In-Reply-To: <20140709141631.GE9918@twins.programming.kicks-ass.net> Accept-Language: zh-CN, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.239.127.40] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On Tue, Jul 08, 2014 at 09:49:40AM -0700, kan.liang@intel.com wrote: > > +/* > > + * Under certain circumstances, access certain MSR may cause #GP. > > + * The function tests if the input MSR can be safely accessed. > > + */ > > +static inline bool check_msr(unsigned long msr) { > > + u64 value; > > + > > + if (rdmsrl_safe(msr, &value) < 0) > > + return false; > > + if (wrmsrl_safe(msr, value) < 0) > > + return false; > > + return true; > > +} > > What does this thing return after patch 2? does the write still fault or will > KVM silently take writes too? If applying patch 2, the function will return true. The KVM just simply ignore the reads/writes.