From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37201) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bjoQW-00055s-Ht for qemu-devel@nongnu.org; Tue, 13 Sep 2016 10:11:13 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bjoQQ-0004om-P6 for qemu-devel@nongnu.org; Tue, 13 Sep 2016 10:11:07 -0400 Received: from mx1.redhat.com ([209.132.183.28]:44510) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bjoQQ-0004oT-JH for qemu-devel@nongnu.org; Tue, 13 Sep 2016 10:11:02 -0400 Date: Tue, 13 Sep 2016 17:11:00 +0300 From: "Michael S. Tsirkin" Message-ID: <20160913170926-mutt-send-email-mst@kernel.org> References: <1473674889-2727-1-git-send-email-davidkiarie4@gmail.com> <1473674889-2727-5-git-send-email-davidkiarie4@gmail.com> <20160912113450.GH3776@pxdev.xzpeter.org> <20160912121122.GJ3776@pxdev.xzpeter.org> <20160913073838.GK3776@pxdev.xzpeter.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160913073838.GK3776@pxdev.xzpeter.org> Subject: Re: [Qemu-devel] [v4 4/6] hw/iommu: AMD IOMMU interrupt remapping List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Xu Cc: David Kiarie , QEMU Developers , Jan Kiszka , rkrcmar@redhat.com, Eduardo Habkost , Paolo Bonzini , Alex Williamson On Tue, Sep 13, 2016 at 03:38:38PM +0800, Peter Xu wrote: > On Mon, Sep 12, 2016 at 03:45:48PM +0300, David Kiarie wrote: > > > When we say cache here, we are mostly talking about GSI routes in > > > kernel, right? Since we still don't have other kind of interrupt > > > caches AFAIK. If so, GSI routes should already been setup even if the > > > interrupts are not triggered for a single time. So we need to > > > invalidate them even ir_cache == false. > > > > > > > You're right but I'm not sure how to implement that while avoiding > > triggering the notifier numerous pointless times during boot. > > > > > > > I think the problem is why cache invalidations during boot will bug > > > the system. Any clue? > > > > > > > The issue is not too many invalidations. I don't have a very clear idea of > > how notifiers work but I would assume it spawns a thread or they somehow > > use a multithreaded approach which would mean triggering the notifier too > > many times within a very short period many trigger a bunch of issues. > > No thread is spawn, we just call the notifier callbacks. > > For me it's fairly acceptable that guest sends lots of invalidations > during boot. That should not lead to any functional issues. If there > is, then something might be wrong. > > I don't know whether mst will like to merge this series even without > fixing this. Anyway I would still prefer to root cause the issue, or > at least comment this out in the commit message (or codes somewhere) > so that we know there is something TBD and might cause misterious > troubles... > > Thanks, > > -- peterx By now it's minimally intrusive, so yes, I think I'll merge and we can apply fixes on top incrementally. E.g. would you like to post the suggested comment as a patch? -- MST