From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH 0/8][v2] MSI-X mask emulation support for assigned device Date: Wed, 20 Oct 2010 17:23:49 +0200 Message-ID: <4CBF0985.408@redhat.com> References: <1287563192-29685-1-git-send-email-sheng@linux.intel.com> <4CBEBB85.4000706@redhat.com> <20101020104447.GD12878@redhat.com> <1287586034.3007.12.camel@x201> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: "Michael S. Tsirkin" , Sheng Yang , Marcelo Tosatti , kvm@vger.kernel.org To: Alex Williamson Return-path: Received: from mx1.redhat.com ([209.132.183.28]:4401 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753727Ab0JTPXy (ORCPT ); Wed, 20 Oct 2010 11:23:54 -0400 In-Reply-To: <1287586034.3007.12.camel@x201> Sender: kvm-owner@vger.kernel.org List-ID: On 10/20/2010 04:47 PM, Alex Williamson wrote: > > > > With current VFIO we would catch mask writes in qemu and > > call a KVM ioctl. We would also need an ioctl to retrieve > > pending bits long term. > > Ugh, no. VFIO us currently independent of KVM. I'd like to keep it > that way. Me, too. Perhaps even more than you. > We'll need to optimize interrupt injection and eoi via KVM, > but it should only be a performance optimization, not a functional > requirement. For level-triggered interrupts only, yes? MSI EOI does not involve any device or interrupt controller visible action? > It would probably make sense to request a mask/unmask ioctl in VFIO for > MSI-X, then perhaps the pending bits would only support read/write (no > mmap), so we could avoid an ioctl there. I would much like to see in-band information (which mask/unmask is for older Linux) done via eventfds so userspace is not involved. -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain.