From: "Michael S. Tsirkin" <mst@redhat.com>
To: David Gibson <david@gibson.dropbear.id.au>
Cc: aliguori@us.ibm.com, aik@ozlabs.ru, rusty@rustcorp.com.au,
qemu-devel@nongnu.org, agraf@suse.de, pbonzini@redhat.com
Subject: Re: [Qemu-devel] [PATCH] virtio: Make memory barriers be memory barriers
Date: Thu, 1 Sep 2011 18:30:21 +0300 [thread overview]
Message-ID: <20110901153020.GB10989@redhat.com> (raw)
In-Reply-To: <1314857389-13363-1-git-send-email-david@gibson.dropbear.id.au>
On Thu, Sep 01, 2011 at 04:09:49PM +1000, David Gibson wrote:
> The virtio code already has memory barrier wmb() macros in the code.
> However they are was defined as no-ops. The comment claims that real
> barriers are not necessary because the code does not run concurrent.
> However, with kvm and io-thread enabled, this is not true and this qemu
> code can indeed run concurrently with the guest kernel. This does not
> cause problems on x86 due to it's strongly ordered storage model, but it
> causes a race leading to virtio errors on POWER which has a relaxed storage
> ordering model.
Why not limit the change to ppc then?
--
MST
next prev parent reply other threads:[~2011-09-01 15:29 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-01 6:09 [Qemu-devel] [PATCH] virtio: Make memory barriers be memory barriers David Gibson
2011-09-01 6:47 ` Paolo Bonzini
2011-09-02 0:08 ` David Gibson
2011-09-02 6:49 ` Paolo Bonzini
2011-09-03 11:53 ` Blue Swirl
2011-09-01 7:37 ` Sasha Levin
2011-09-01 7:38 ` Sasha Levin
2011-09-01 7:56 ` Paolo Bonzini
2011-09-02 0:09 ` David Gibson
2011-09-01 15:30 ` Michael S. Tsirkin [this message]
2011-09-01 16:14 ` Paolo Bonzini
2011-09-01 16:34 ` Michael S. Tsirkin
2011-09-01 20:31 ` Paolo Bonzini
2011-09-02 15:45 ` Michael S. Tsirkin
2011-09-03 14:46 ` David Gibson
2011-09-04 9:16 ` Michael S. Tsirkin
2011-09-05 4:43 ` David Gibson
2011-09-05 9:19 ` Michael S. Tsirkin
2011-09-06 3:12 ` David Gibson
2011-09-06 6:55 ` Paolo Bonzini
2011-09-06 9:02 ` David Gibson
2011-09-06 9:28 ` Avi Kivity
2011-09-06 9:35 ` Michael S. Tsirkin
2011-09-06 9:38 ` Paolo Bonzini
2011-09-05 7:41 ` Paolo Bonzini
2011-09-05 8:06 ` Michael S. Tsirkin
2011-09-05 9:42 ` Paolo Bonzini
2011-09-03 16:19 ` Paolo Bonzini
2011-09-04 8:47 ` Michael S. Tsirkin
2011-09-02 0:11 ` David Gibson
2011-09-02 6:11 ` Paolo Bonzini
2011-09-02 15:57 ` Michael S. Tsirkin
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