From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755520Ab2GJMuv (ORCPT ); Tue, 10 Jul 2012 08:50:51 -0400 Received: from mx1.redhat.com ([209.132.183.28]:40864 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752022Ab2GJMuu (ORCPT ); Tue, 10 Jul 2012 08:50:50 -0400 Message-ID: <4FFC251F.4050504@redhat.com> Date: Tue, 10 Jul 2012 15:50:39 +0300 From: Avi Kivity User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:13.0) Gecko/20120615 Thunderbird/13.0.1 MIME-Version: 1.0 To: Gleb Natapov CC: Xiao Guangrong , Marcelo Tosatti , LKML , KVM Subject: Re: [PATCH 1/2] KVM: X86: remove read buffer for mmio read References: <4FFA9E16.10001@linux.vnet.ibm.com> <4FFABD59.2070108@redhat.com> <20120709112346.GA23898@redhat.com> <4FFAD341.3080508@redhat.com> <4FFADB37.4090705@linux.vnet.ibm.com> <4FFADDFA.5000603@redhat.com> <20120710103629.GC23898@redhat.com> <4FFC07BB.8080802@redhat.com> <20120710104847.GD23898@redhat.com> In-Reply-To: <20120710104847.GD23898@redhat.com> X-Enigmail-Version: 1.4.2 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/10/2012 01:48 PM, Gleb Natapov wrote: > > > > > > > But the code is already here, why drop it? > > > > The read cache is not effective for multiple disjunct reads. > What do you mean? If an instruction reads from several sources in mmio, then the first read will be flushed from the cache by the second read. So if we need a third read, we'll have to exit for the first again. -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain.