From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753313Ab2GILPp (ORCPT ); Mon, 9 Jul 2012 07:15:45 -0400 Received: from mx1.redhat.com ([209.132.183.28]:20092 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753108Ab2GILPo (ORCPT ); Mon, 9 Jul 2012 07:15:44 -0400 Message-ID: <4FFABD59.2070108@redhat.com> Date: Mon, 09 Jul 2012 14:15:37 +0300 From: Avi Kivity User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:13.0) Gecko/20120605 Thunderbird/13.0 MIME-Version: 1.0 To: Xiao Guangrong CC: Marcelo Tosatti , LKML , KVM Subject: Re: [PATCH 1/2] KVM: X86: remove read buffer for mmio read References: <4FFA9E16.10001@linux.vnet.ibm.com> In-Reply-To: <4FFA9E16.10001@linux.vnet.ibm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/09/2012 12:02 PM, Xiao Guangrong wrote: > After commit f78146b0f9230765c6315b2e14f56112513389ad: > > KVM: Fix page-crossing MMIO > > MMIO that are split across a page boundary are currently broken - the > code does not expect to be aborted by the exit to userspace for the > first MMIO fragment. > > This patch fixes the problem by generalizing the current code for handling > 16-byte MMIOs to handle a number of "fragments", and changes the MMIO > code to create those fragments. > > Signed-off-by: Avi Kivity > Signed-off-by: Marcelo Tosatti > > Multiple MMIO reads can be merged into mmio_fragments, the read buffer is not > needed anymore > > Signed-off-by: Xiao Guangrong > --- > arch/x86/include/asm/kvm_emulate.h | 1 - > arch/x86/kvm/emulate.c | 43 ++++------------------------------- > arch/x86/kvm/x86.c | 2 - > 3 files changed, 5 insertions(+), 41 deletions(-) > > diff --git a/arch/x86/include/asm/kvm_emulate.h b/arch/x86/include/asm/kvm_emulate.h > index 1ac46c22..339d7c6 100644 > --- a/arch/x86/include/asm/kvm_emulate.h > +++ b/arch/x86/include/asm/kvm_emulate.h > @@ -286,7 +286,6 @@ struct x86_emulate_ctxt { > struct operand *memopp; > struct fetch_cache fetch; > struct read_cache io_read; > - struct read_cache mem_read; > }; > Suppose we have a RMW instruction. On the first entry to x86_emulate_insn() we'll drop to userspace and perform the read, and the seconds we'll read from the cache and complete the write. Without the read cache this cannot work. kvm-unit-tests.git has a test for xchg to mmio. Does it still work? I agree this code has to go, but it needs to be replaced by something. Maybe a .valid flag in struct operand. -- error compiling committee.c: too many arguments to function