From: Rusty Russell <rusty@rustcorp.com.au>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: virtualization <virtualization@lists.linux-foundation.org>,
Rafael Aquini <aquini@redhat.com>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH RFC] virtio-balloon: fix add/get API use
Date: Wed, 04 Jul 2012 12:57:40 +0930 [thread overview]
Message-ID: <87ipe4w6hf.fsf@rustcorp.com.au> (raw)
In-Reply-To: <20120702073308.GB8268@redhat.com>
On Mon, 2 Jul 2012 10:33:08 +0300, "Michael S. Tsirkin" <mst@redhat.com> wrote:
> In virtio balloon virtqueue_get_buf might now run concurrently with
> virtqueue_kick. I audited both and this seems safe in practice but
> this is not guaranteed by the API.
> Additionally, a spurious interrupt might in theory make
> virtqueue_get_buf run in parallel with virtqueue_add_buf, which is racy.
>
> While we might try to protect against spurious callbacks it's
> easier to fix the driver: balloon seems to be the only one
> (mis)using the API like this, so let's just fix balloon.
>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
I was thinking of a spinlock, but this is far more elegant.
And I added an explicit reference to the 'virtio: expose added
descriptors immediately.' commit in your commit msg.
Kudos!
Rusty.
WARNING: multiple messages have this Message-ID (diff)
From: Rusty Russell <rusty@rustcorp.com.au>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Rafael Aquini <aquini@redhat.com>,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
virtualization <virtualization@lists.linux-foundation.org>
Subject: Re: [PATCH RFC] virtio-balloon: fix add/get API use
Date: Wed, 04 Jul 2012 12:57:40 +0930 [thread overview]
Message-ID: <87ipe4w6hf.fsf@rustcorp.com.au> (raw)
In-Reply-To: <20120702073308.GB8268@redhat.com>
On Mon, 2 Jul 2012 10:33:08 +0300, "Michael S. Tsirkin" <mst@redhat.com> wrote:
> In virtio balloon virtqueue_get_buf might now run concurrently with
> virtqueue_kick. I audited both and this seems safe in practice but
> this is not guaranteed by the API.
> Additionally, a spurious interrupt might in theory make
> virtqueue_get_buf run in parallel with virtqueue_add_buf, which is racy.
>
> While we might try to protect against spurious callbacks it's
> easier to fix the driver: balloon seems to be the only one
> (mis)using the API like this, so let's just fix balloon.
>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
I was thinking of a spinlock, but this is far more elegant.
And I added an explicit reference to the 'virtio: expose added
descriptors immediately.' commit in your commit msg.
Kudos!
Rusty.
next prev parent reply other threads:[~2012-07-04 3:27 UTC|newest]
Thread overview: 60+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <patchbomb.1320306168@localhost6.localdomain6>
2011-11-03 7:42 ` [PATCH 1 of 5] virtio: document functions better Rusty Russell
2011-11-03 7:42 ` Rusty Russell
2011-11-03 7:49 ` Christoph Hellwig
2011-11-03 7:49 ` Christoph Hellwig
2011-11-03 7:42 ` [PATCH 2 of 5] virtio: rename virtqueue_add_buf_gfp to virtqueue_add_buf Rusty Russell
2011-11-03 7:42 ` Rusty Russell
2011-11-03 7:50 ` Christoph Hellwig
2011-11-03 7:50 ` Christoph Hellwig
2011-11-03 7:42 ` [PATCH 3 of 5] virtio: support unlocked queue kick Rusty Russell
2011-11-03 7:42 ` Rusty Russell
2011-11-03 7:52 ` Christoph Hellwig
2011-11-04 10:09 ` Stefan Hajnoczi
2011-11-04 10:09 ` Stefan Hajnoczi
2011-11-04 10:36 ` Rusty Russell
2011-11-04 10:36 ` Rusty Russell
2011-11-04 10:36 ` Rusty Russell
2011-11-03 7:52 ` Christoph Hellwig
2011-11-03 7:42 ` [PATCH 4 of 5] virtio: avoid modulus operation Rusty Russell
2011-11-03 7:42 ` Rusty Russell
2011-11-03 7:51 ` Pekka Enberg
2011-11-03 7:51 ` Pekka Enberg
2011-11-03 10:18 ` Rusty Russell
2011-11-03 10:18 ` Rusty Russell
2011-11-03 7:42 ` [PATCH 5 of 5] virtio: expose added descriptors immediately Rusty Russell
2011-11-03 7:42 ` Rusty Russell
2011-11-13 21:03 ` Michael S. Tsirkin
2011-11-13 21:03 ` Michael S. Tsirkin
2011-11-14 0:43 ` Rusty Russell
2011-11-14 0:43 ` Rusty Russell
2011-11-14 0:43 ` Rusty Russell
2011-11-14 6:56 ` Michael S. Tsirkin
2011-11-16 0:21 ` Rusty Russell
2011-11-16 7:18 ` Michael S. Tsirkin
2011-11-21 1:48 ` Rusty Russell
2011-11-21 11:57 ` Michael S. Tsirkin
2011-11-22 0:33 ` Rusty Russell
2011-11-22 6:29 ` Michael S. Tsirkin
2011-11-23 1:19 ` Rusty Russell
2011-11-23 8:30 ` Michael S. Tsirkin
2012-07-01 9:20 ` RFD: virtio balloon API use (was Re: [PATCH 5 of 5] virtio: expose added descriptors immediately) Michael S. Tsirkin
2012-07-01 9:20 ` Michael S. Tsirkin
2012-07-02 1:05 ` Rusty Russell
2012-07-02 1:05 ` Rusty Russell
2012-07-02 7:25 ` Michael S. Tsirkin
2012-07-02 7:25 ` Michael S. Tsirkin
2012-07-02 16:08 ` Rafael Aquini
2012-07-02 16:08 ` Rafael Aquini
2012-07-03 0:47 ` Rusty Russell
2012-07-03 16:26 ` Rafael Aquini
2012-07-03 16:26 ` Rafael Aquini
2012-07-04 10:55 ` Michael S. Tsirkin
2012-07-04 10:55 ` Michael S. Tsirkin
2012-07-08 23:39 ` Rusty Russell
2012-07-08 23:39 ` Rusty Russell
2012-07-04 10:55 ` Michael S. Tsirkin
2012-07-04 10:55 ` Michael S. Tsirkin
2012-07-02 7:33 ` [PATCH RFC] virtio-balloon: fix add/get API use Michael S. Tsirkin
2012-07-02 7:33 ` Michael S. Tsirkin
2012-07-04 3:27 ` Rusty Russell [this message]
2012-07-04 3:27 ` Rusty Russell
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