From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marcelo Tosatti Subject: Re: [PATCH 0/3] Emulate MSI-X mask bits for assigned devices Date: Thu, 30 Sep 2010 13:44:51 -0300 Message-ID: <20100930164451.GC29881@amt.cnet> References: <1285667052-24907-1-git-send-email-sheng@linux.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Avi Kivity , kvm@vger.kernel.org To: Sheng Yang Return-path: Received: from mx1.redhat.com ([209.132.183.28]:8708 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756749Ab0I3Qpk (ORCPT ); Thu, 30 Sep 2010 12:45:40 -0400 Content-Disposition: inline In-Reply-To: <1285667052-24907-1-git-send-email-sheng@linux.intel.com> Sender: kvm-owner@vger.kernel.org List-ID: On Tue, Sep 28, 2010 at 05:44:09PM +0800, Sheng Yang wrote: > Hi Avi & Marcelo > > This patchset would add emulation of MSI-X mask bit for assigned devices in > QEmu. > > BTW: We are also purposed an acceleration of MSI-X mask bit for KVM - to get > it done in kernel. That's because sometime MSI-X mask bit was accessed very > frequently by guest and emulation in QEmu cost a lot(tens to hundreds percent > CPU utilization sometime), e.g. guest using Linux 2.6.18 or under some heavy > workload. The method has been proved efficient in Xen, but it would require > VMM to handle MSI-X table. Is that OK with you? It would be good to understand where that cost is, before. Eg. do you commit kvm irq route frequently when guest unmasks?