[SeaBIOS] [PATCH seabios 3/3] kvmtool: support larger virtio queues

Jean-Philippe Brucker jean-philippe.brucker at arm.com
Fri Nov 3 14:49:32 CET 2017


On 02/11/17 15:50, Gerd Hoffmann wrote:
> Queues have 256 entries on kvmtool, support that.  Needs more memory for
> virtqueues now.  But with the move to 32bit drivers for virtio this
> should not be much of an issue any more.
> 
> Known problems (probably kvmtool bugs):
>  * Must bump to 260 entries to make things actually work,
>    otherwise kvmtool segfaults.  Oops.

You mean setting MAX_QUEUE_NUM to 256 instead of 260 in seabios causes a
kvmtool crash? Do you have any more detail on the segfault?

One problem I can see is kvmtool's handling of used/avail event indexes.
net and blk devices call virtio_queue__should_signal which reads event
indexes without of checking if VIRTIO_F_EVENT_IDX was negotiated first.
Since seabios doesn't use the event indexes, this would lead to missing
signals, but not a segfault.

>  * Linux kernel doesn't find virtio-blk devices after seabios
>    initialized them.  virtio device reset not working properly?

No, reset isn't implemented at all... A lot of work is required to
properly clear the state and threads of each device.

Thanks,
Jean



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