From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from [140.186.70.92] (port=39953 helo=eggs.gnu.org)
	by lists.gnu.org with esmtp (Exim 4.43) id 1Phlhd-0007ei-UR
	for qemu-devel@nongnu.org; Tue, 25 Jan 2011 11:25:11 -0500
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <stefanha@gmail.com>) id 1PhlhZ-00042T-Al
	for qemu-devel@nongnu.org; Tue, 25 Jan 2011 11:25:06 -0500
Received: from mail-yw0-f45.google.com ([209.85.213.45]:48981)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <stefanha@gmail.com>) id 1PhlhZ-00042L-8L
	for qemu-devel@nongnu.org; Tue, 25 Jan 2011 11:25:05 -0500
Received: by ywa8 with SMTP id 8so1603943ywa.4
	for <qemu-devel@nongnu.org>; Tue, 25 Jan 2011 08:25:04 -0800 (PST)
MIME-Version: 1.0
In-Reply-To: <20110125145657.GD15666@redhat.com>
References: <1295967211-362-1-git-send-email-stefanha@linux.vnet.ibm.com>
	<20110125145657.GD15666@redhat.com>
Date: Tue, 25 Jan 2011 16:25:04 +0000
Message-ID: <AANLkTimEy7AGFd59oB+wesbLoSD6M+bE52Pe0a1D=6JB@mail.gmail.com>
Subject: Re: [Qemu-devel] Re: [PATCH v2] virtio-pci: Disable virtio-ioeventfd
	when !CONFIG_IOTHREAD
From: Stefan Hajnoczi <stefanha@gmail.com>
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable
List-Id: qemu-devel.nongnu.org
List-Unsubscribe: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.nongnu.org/archive/html/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Kevin Wolf <kwolf@redhat.com>, Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>, qemu-devel@nongnu.org

On Tue, Jan 25, 2011 at 2:56 PM, Michael S. Tsirkin <mst@redhat.com> wrote:
> On Tue, Jan 25, 2011 at 02:53:31PM +0000, Stefan Hajnoczi wrote:
>> It is not possible to use virtio-ioeventfd when building without an I/O
>> thread. =A0We rely on a signal to kick us out of vcpu execution. =A0Time=
rs
>> and AIO use SIGALRM and SIGUSR2 respectively. =A0Unfortunately eventfd
>> does not support O_ASYNC (SIGIO) so eventfd cannot be used in a signal
>> driven manner.
>>
>> Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
>> ---
>> =A0kvm-all.c | =A0 =A08 ++++++--
>> =A01 files changed, 6 insertions(+), 2 deletions(-)
>>
>> diff --git a/kvm-all.c b/kvm-all.c
>> index 255b6fa..881ea32 100644
>> --- a/kvm-all.c
>> +++ b/kvm-all.c
>> @@ -449,10 +449,14 @@ int kvm_check_extension(KVMState *s, unsigned int =
extension)
>>
>> =A0static int kvm_check_many_ioeventfds(void)
>> =A0{
>> - =A0 =A0/* Older kernels have a 6 device limit on the KVM io bus. =A0Fi=
nd out so we
>> + =A0 =A0/* Userspace can use ioeventfd for virtqueue kick. =A0This requ=
ires a host
>
> virtqueue kick -> io notifications?

Fixed in v3.

Stefan