Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753299Ab3FII4w (ORCPT ); Sun, 9 Jun 2013 04:56:52 -0400 Received: from mail-pa0-f48.google.com ([209.85.220.48]:64509 "EHLO mail-pa0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750827Ab3FII4u (ORCPT ); Sun, 9 Jun 2013 04:56:50 -0400 Message-ID: <51B4434A.2010402@gmail.com> Date: Sun, 09 Jun 2013 16:56:42 +0800 From: Xiao Guangrong User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130510 Thunderbird/17.0.6 MIME-Version: 1.0 To: Gleb Natapov CC: Paolo Bonzini , Marcelo Tosatti , LKML , KVM Subject: Re: [PATCH] KVM: x86: fix missed memory synchronization when patch hypercall References: <51B2A1D9.6060306@gmail.com> <20130609084526.GH4725@redhat.com> In-Reply-To: <20130609084526.GH4725@redhat.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 Content-Length: 1461 Lines: 32 On 06/09/2013 04:45 PM, Gleb Natapov wrote: > On Sat, Jun 08, 2013 at 11:15:37AM +0800, Xiao Guangrong wrote: >> From: Xiao Guangrong >> >> Currently, memory synchronization is missed in emulator_fix_hypercall, >> please see the commit 758ccc89b83 >> (KVM: x86: drop calling kvm_mmu_zap_all in emulator_fix_hypercall) >> >> This patch fixes it by introducing kvm_vcpus_hang_on_page_start() and >> kvm_vcpus_hang_on_page_end which unmap the patched page from guest >> and use kvm_flush_remote_tlbs() as the serializing instruction to >> ensure the memory coherence >> [ The SDM said that INVEPT, INVVPID and MOV (to control register, with >> the exception of MOV CR8) are the serializing instructions. ] >> >> The mmu-lock is held during host patches the page so that it stops vcpus >> to fix its further page fault >> > I have a patch to implement is much simple and in generic way, not > relying on MMU internals. I have considered this way but it seems not simple - it needs a new type of request and it forces all vcpus to hang when host is patching the page. My approach is just reusing the mmu code and requires vcpus to hang only when the patched page is bing accessed. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/