Re: [KVM PATCH v9 0/5] irqfd fixes and enhancements

From: "Michael S. Tsirkin" <mst@redhat.com>
To: Avi Kivity <avi@redhat.com>
Cc: Gregory Haskins <ghaskins@novell.com>,
	kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
	davidel@xmailserver.org
Subject: Re: [KVM PATCH v9 0/5] irqfd fixes and enhancements
Date: Sun, 5 Jul 2009 13:20:43 +0300	[thread overview]
Message-ID: <20090705102043.GA3798@redhat.com> (raw)
In-Reply-To: <20090705101623.GA3014@redhat.com>

On Sun, Jul 05, 2009 at 01:16:24PM +0300, Michael S. Tsirkin wrote:
> On Sun, Jul 05, 2009 at 12:28:30PM +0300, Avi Kivity wrote:
> > On 07/02/2009 06:50 PM, Avi Kivity wrote:
> >> On 07/02/2009 06:37 PM, Gregory Haskins wrote:
> >>> (Applies to kvm.git/master:1f9050fd)
> >>>
> >>> The following is the latest attempt to fix the races in  
> >>> irqfd/eventfd, as
> >>> well as restore DEASSIGN support.  For more details, please read the  
> >>> patch
> >>> headers.
> >>>
> >>> As always, this series has been tested against the kvm-eventfd unit test
> >>> and everything appears to be functioning properly. You can download this
> >>> test here:
> >>
> >> Applied, thanks.
> >>
> >
> > ... and unapplied.  There's a refcounting mismatch in irqfd_cleanup: a  
> > reference is taken for each irqfd, but dropped for each guest.  This  
> > causes an oops if a guest with no irqfds is created and destroyed:
> 
> Ugh, apparently this logic has been changed between I acked v7 of the
> patches and between Avi applied v9. Will have to find the time to redo
> the review - or maybe just go back to v7? Is on-demand wq creation
> really that important?

Avi, is it true that just reverting the last patch in series,
c9a2686e39e9095772ec6453f89c417a8e166f11, fixes the issue?

-- 
MST