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Date: Wed, 20 Dec 2017 06:23:31 +0200
From: "Michael S. Tsirkin" <mst@redhat.com>
Message-ID: <20171220061755-mutt-send-email-mst@kernel.org>
References: <1513350170-20168-1-git-send-email-den@openvz.org>
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Subject: Re: [Qemu-devel] [PATCH v3 0/2] virtio: fix IO request length in
 virtio SCSI/block
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To: "Denis V. Lunev" <den@openvz.org>
Cc: qemu-devel@nongnu.org, Stefan Hajnoczi <stefanha@redhat.com>, Kevin Wolf <kwolf@redhat.com>, Max Reitz <mreitz@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>, Richard Henderson <rth@twiddle.net>, Eduardo Habkost <ehabkost@redhat.com>, kraxel@redhat.com

On Fri, Dec 15, 2017 at 06:02:48PM +0300, Denis V. Lunev wrote:
> v2->v3
> - added 2.12 machine types
> - added compat properties for 2.11 machine type
> 
> v1->v2:
> - added max_segments property for virtblock device

I'm not applying this for now.

It seems too easy to create illegal configurations with it,
e.g. where max seg > queue size.

1022 also seems too aggressive - e.g. if a couple of segments
cross page boundaries, we'll exceed the iov length. around
500 seems more prudent.

Guerd, could you pls also take a look at whether seabios is
smart enough to downgrade if guest queue size is too big?

> Signed-off-by: Denis V. Lunev <den@openvz.org>
> CC: "Michael S. Tsirkin" <mst@redhat.com>
> CC: Stefan Hajnoczi <stefanha@redhat.com>
> CC: Kevin Wolf <kwolf@redhat.com>
> CC: Max Reitz <mreitz@redhat.com>
> CC: Paolo Bonzini <pbonzini@redhat.com>
> CC: Richard Henderson <rth@twiddle.net>
> CC: Eduardo Habkost <ehabkost@redhat.com>