From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755824Ab2BOV7m (ORCPT ); Wed, 15 Feb 2012 16:59:42 -0500 Received: from mail-pw0-f46.google.com ([209.85.160.46]:48384 "EHLO mail-pw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755071Ab2BOV7j (ORCPT ); Wed, 15 Feb 2012 16:59:39 -0500 Message-ID: <4F3C2AC5.80400@codemonkey.ws> Date: Wed, 15 Feb 2012 15:59:33 -0600 From: Anthony Liguori User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.23) Gecko/20110922 Lightning/1.0b2 Thunderbird/3.1.15 MIME-Version: 1.0 To: Avi Kivity CC: Rusty Russell , qemu-devel , KVM list , Gleb Natapov , linux-kernel Subject: Re: [Qemu-devel] [RFC] Next gen kvm api References: <4F2AB552.2070909@redhat.com> <20120205093723.GQ23536@redhat.com> <4F2E4F8B.8090504@redhat.com> <20120205095153.GA29265@redhat.com> <4F2EAFF6.7030006@codemonkey.ws> <4F2F9E89.7090607@redhat.com> <87vcnih5qt.fsf@rustcorp.com.au> <4F3BB59D.2020505@redhat.com> In-Reply-To: <4F3BB59D.2020505@redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/15/2012 07:39 AM, Avi Kivity wrote: > On 02/07/2012 08:12 PM, Rusty Russell wrote: >>> I would really love to have this, but the problem is that we'd need a >>> general purpose bytecode VM with binding to some kernel APIs. The >>> bytecode VM, if made general enough to host more complicated devices, >>> would likely be much larger than the actual code we have in the kernel now. >> >> We have the ability to upload bytecode into the kernel already. It's in >> a great bytecode interpreted by the CPU itself. > > Unfortunately it's inflexible (has to come with the kernel) and open to > security vulnerabilities. I wonder if there's any reasonable way to run device emulation within the context of the guest. Could we effectively do something like SMM? For a given set of traps, reflect back into the guest quickly changing the visibility of the VGA region. It may require installing a new CR3 but maybe that wouldn't be so bad with VPIDs. Then you could implement the PIT as guest firmware using kvmclock as the time base. Once you're back in the guest, you could install the old CR3. Perhaps just hide a portion of the physical address space with the e820. Regards, Anthony Liguori >> If every user were emulating different machines, LPF this would make >> sense. Are they? > > They aren't. > >> Or should we write those helpers once, in C, and >> provide that for them. > > There are many of them: PIT/PIC/IOAPIC/MSIX tables/HPET/kvmclock/Hyper-V > stuff/vhost-net/DMA remapping/IO remapping (just for x86), and some of > them are quite complicated. However implementing them in bytecode > amounts to exposing a stable kernel ABI, since they use such a vast > range of kernel services. >