From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755777Ab2GJNB7 (ORCPT ); Tue, 10 Jul 2012 09:01:59 -0400 Received: from mx1.redhat.com ([209.132.183.28]:37563 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755744Ab2GJNB4 (ORCPT ); Tue, 10 Jul 2012 09:01:56 -0400 Date: Tue, 10 Jul 2012 16:01:50 +0300 From: Gleb Natapov To: Avi Kivity Cc: Xiao Guangrong , Marcelo Tosatti , LKML , KVM Subject: Re: [PATCH 1/2] KVM: X86: remove read buffer for mmio read Message-ID: <20120710130149.GE23898@redhat.com> 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> <4FFC251F.4050504@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4FFC251F.4050504@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jul 10, 2012 at 03:50:39PM +0300, Avi Kivity wrote: > 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. > The cache is flashed only before instruction decode, never during emulation. -- Gleb.