From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gleb Natapov Subject: Re: [PATCH] get rid of mmu_only parameter in emulator_write_emulated() Date: Tue, 13 Apr 2010 10:40:59 +0300 Message-ID: <20100413074059.GH23554@redhat.com> References: <20100413072156.GF23554@redhat.com> <4BC41C38.5080403@redhat.com> <20100413072643.GG23554@redhat.com> <4BC41ED9.1000506@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: kvm@vger.kernel.org, mtosatti@redhat.com To: Avi Kivity Return-path: Received: from mx1.redhat.com ([209.132.183.28]:28415 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752190Ab0DMHlB (ORCPT ); Tue, 13 Apr 2010 03:41:01 -0400 Received: from int-mx05.intmail.prod.int.phx2.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.18]) by mx1.redhat.com (8.13.8/8.13.8) with ESMTP id o3D7f0wR004505 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Tue, 13 Apr 2010 03:41:00 -0400 Content-Disposition: inline In-Reply-To: <4BC41ED9.1000506@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On Tue, Apr 13, 2010 at 10:35:53AM +0300, Avi Kivity wrote: > On 04/13/2010 10:26 AM, Gleb Natapov wrote: > >On Tue, Apr 13, 2010 at 10:24:40AM +0300, Avi Kivity wrote: > >>On 04/13/2010 10:21 AM, Gleb Natapov wrote: > >>>May be I am missing something here, but it seams we can call > >>>kvm_mmu_pte_write() directly from emulator_cmpxchg_emulated() > >>>instead of passing mmu_only down to emulator_write_emulated_onepage() > >>>and call it there. > >>> > >>> > >>>@@ -3460,7 +3444,9 @@ static int emulator_cmpxchg_emulated(unsigned long addr, > >>> if (!exchanged) > >>> return X86EMUL_CMPXCHG_FAILED; > >>> > >>>- return __emulator_write_emulated(addr, new, bytes, vcpu, true); > >>>+ kvm_mmu_pte_write(vcpu, gpa, new, bytes, 1); > >>>+ > >>>+ return X86EMUL_CONTINUE; > >>> > >>The written range might cross a page boundary, which > >>kvm_mmu_pte_write() is not prepared to handle. > >> > >Don't we emulate exchange as write in this case? > > > > if (((gpa + bytes - 1)& PAGE_MASK) != (gpa& PAGE_MASK)) > > goto emul_write; > > We do, but that's unrelated. We still have to invalidate potential > ptes on both pages > The code path executed in case of cmpxchg crossing page boundary is not touched by the patch as far as I can see. In this case emulator_write_emulated() is executed with mmu_only false and kvm_mmu_pte_write() is called from emulator_write_phys(). -- Gleb.