Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753410Ab3FII7l (ORCPT ); Sun, 9 Jun 2013 04:59:41 -0400 Received: from mx1.redhat.com ([209.132.183.28]:46204 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752583Ab3FII7k (ORCPT ); Sun, 9 Jun 2013 04:59:40 -0400 Date: Sun, 9 Jun 2013 11:59:38 +0300 From: Gleb Natapov To: Xiao Guangrong Cc: Paolo Bonzini , Marcelo Tosatti , LKML , KVM Subject: Re: [PATCH] KVM: x86: fix missed memory synchronization when patch hypercall Message-ID: <20130609085937.GJ4725@redhat.com> References: <51B2A1D9.6060306@gmail.com> <20130609084526.GH4725@redhat.com> <51B4434A.2010402@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <51B4434A.2010402@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1645 Lines: 37 On Sun, Jun 09, 2013 at 04:56:42PM +0800, Xiao Guangrong wrote: > 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. That's very rare, no point to optimize this code path. -- Gleb. -- 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/