From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Gleixner Subject: Re: [PATCH 2/2] Device assignment: Fix MSI IRQ affinity setting Date: Fri, 25 May 2012 01:56:09 +0200 (CEST) Message-ID: References: <1337878924-39069-1-git-send-email-richard@nod.at> <1337878924-39069-2-git-send-email-richard@nod.at> <1337883627.4714.32.camel@ul30vt> <4FBEADCB.2010900@siemens.com> <1337897506.4714.55.camel@ul30vt> <1337901828.4714.82.camel@ul30vt> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Cc: Jan Kiszka , Richard Weinberger , kvm@vger.kernel.org, avi@redhat.com, Marcelo Tosatti , Bjorn Helgaas , "Michael S. Tsirkin" To: Alex Williamson Return-path: Received: from www.linutronix.de ([62.245.132.108]:59341 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752922Ab2EXX4M (ORCPT ); Thu, 24 May 2012 19:56:12 -0400 In-Reply-To: <1337901828.4714.82.camel@ul30vt> Sender: kvm-owner@vger.kernel.org List-ID: On Thu, 24 May 2012, Alex Williamson wrote: > On Fri, 2012-05-25 at 01:01 +0200, Thomas Gleixner wrote: > > So the proper fix is that qemu tells the guest that mask bit is > > supported and catches the mask bit toggling before writing it out to > > the hardware for those devices which do not support it. > > We can't necessarily do that, we have to work with the config space > we're give. Using the smallest possible MSI capability always works. > Adding mask bits may not fit in with the existing capabilities of the > physical device. Thanks, I see what you mean. A random device driver of a random guest OS might rely on that information. Unlikely, but .... So we need some logic to circumvent the masked/unmasked logic in case that property is not set, right ? Thanks, tglx