Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758991AbXH0RaT (ORCPT ); Mon, 27 Aug 2007 13:30:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1760093AbXH0R3R (ORCPT ); Mon, 27 Aug 2007 13:29:17 -0400 Received: from il.qumranet.com ([82.166.9.18]:55571 "EHLO il.qumranet.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758539AbXH0R3P (ORCPT ); Mon, 27 Aug 2007 13:29:15 -0400 Message-ID: <46D3095A.6020305@qumranet.com> Date: Mon, 27 Aug 2007 20:26:50 +0300 From: Avi Kivity User-Agent: Thunderbird 2.0.0.5 (X11/20070719) MIME-Version: 1.0 To: Anthony Liguori CC: kvm-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/3] Implement emulator_write_phys() References: <11882278064002-git-send-email-aliguori@us.ibm.com> <1188227808405-git-send-email-aliguori@us.ibm.com> <46D2F1B7.70604@qumranet.com> <1188235419.6364.2.camel@squirrel> In-Reply-To: <1188235419.6364.2.camel@squirrel> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1579 Lines: 44 Anthony Liguori wrote: > On Mon, 2007-08-27 at 18:45 +0300, Avi Kivity wrote: > >> Anthony Liguori wrote: >> >>> Since a hypercall may span two pages and is a gva, we need a function to write >>> to a gva that may span multiple pages. emulator_write_phys() seems like the >>> logical choice for this. >>> >>> @@ -962,8 +962,35 @@ static int emulator_write_std(unsigned long addr, >>> unsigned int bytes, >>> struct kvm_vcpu *vcpu >>> >> I think that emulator_write_emulated(), except for being awkwardly >> named, should do the job. We have enough APIs. >> >> But! We may not overwrite the hypercall instruction while a vcpu may be >> executing, since there's no atomicity guarantee for code fetch. We have >> to to be out of guest mode while writing that insn. >> > > > Hrm, good catch. > > How can we get out of guest mode given SMP guest support? > > kvm_flush_remote_tlbs() is something that can be generalized. Basically, you set a bit in each vcpu and send an IPI to take them out. But that's deadlock prone and complex. Maybe you can just take kvm->lock, zap the mmu and the flush tlbs, and patch the instruction at your leisure, as no vcpu will be able to map memory until the lock is released. -- Any sufficiently difficult bug is indistinguishable from a feature. - 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/