From: "Michael S. Tsirkin" <mst@redhat.com>
To: Stefan Hajnoczi <stefanha@gmail.com>
Cc: Igor Mammedov <imammedo@redhat.com>, qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [PATCH 1/6] virtio: introduce virtio_map
Date: Tue, 27 Oct 2015 20:34:32 +0200 [thread overview]
Message-ID: <20151027203140-mutt-send-email-mst@redhat.com> (raw)
In-Reply-To: <20151027161954.GG5626@stefanha-x1.localdomain>
On Tue, Oct 27, 2015 at 04:19:54PM +0000, Stefan Hajnoczi wrote:
> On Tue, Oct 27, 2015 at 10:47:56AM +0200, Michael S. Tsirkin wrote:
> > This will still fail if there's no space left in the sg, but luckily max
> > queue size in use is currently 256, while max sg size is 1024, so we
> > should be OK even is all entries happen to cross a single DIMM boundary.
>
> Don't forget about indirect descriptors. They can use all 1024 iovecs,
> regardless of virtqueue size, so virtqueue size of 256 isn't the true
> maximum.
Not according to the spec - virtio spec says vq size is the maximum size
of a chain.
> I'm worried that we could now see failures due to non-contiguous HVAs.
Does linux guest create chains > vq size then? Does it actually
have 1024 hardcoded somewhere?
--
MST
next prev parent reply other threads:[~2015-10-27 18:34 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-27 8:47 [Qemu-devel] [PATCH 0/6] virtio: handle non contigious s/g entries Michael S. Tsirkin
2015-10-27 8:47 ` [Qemu-devel] [PATCH 1/6] virtio: introduce virtio_map Michael S. Tsirkin
2015-10-27 16:13 ` Stefan Hajnoczi
2015-10-27 18:38 ` Michael S. Tsirkin
2015-10-27 16:19 ` Stefan Hajnoczi
2015-10-27 18:34 ` Michael S. Tsirkin [this message]
2015-10-28 11:37 ` Stefan Hajnoczi
2015-10-28 12:16 ` Igor Mammedov
2015-10-28 13:11 ` Igor Mammedov
2015-10-27 8:47 ` [Qemu-devel] [PATCH 2/6] virtio: switch to virtio_map Michael S. Tsirkin
2015-10-28 13:02 ` Igor Mammedov
2015-10-27 8:48 ` [Qemu-devel] [PATCH 3/6] virtio-blk: convert to virtqueue_map Michael S. Tsirkin
2015-10-28 13:02 ` Igor Mammedov
2015-10-27 8:48 ` [Qemu-devel] [PATCH 4/6] virtio-serial: convert to virtio_map Michael S. Tsirkin
2015-10-28 13:03 ` Igor Mammedov
2015-10-27 8:48 ` [Qemu-devel] [PATCH 5/6] virtio-scsi: convert to virtqueue_map Michael S. Tsirkin
2015-10-28 13:03 ` Igor Mammedov
2015-10-27 8:48 ` [Qemu-devel] [PATCH 6/6] virtio: drop virtqueue_map_sg Michael S. Tsirkin
2015-10-28 13:04 ` Igor Mammedov
2015-10-27 8:50 ` [Qemu-devel] [PATCH 0/6] virtio: handle non contigious s/g entries Michael S. Tsirkin
2015-10-27 11:51 ` Michael S. Tsirkin
2015-10-27 16:24 ` Stefan Hajnoczi
2015-10-28 12:30 ` Igor Mammedov
2015-10-27 12:06 ` Cornelia Huck
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