Re: [Qemu-devel] [PATCH v2 for-1.6 0/2] virtio-mmio: fixes to QueueNum, QueueNumMax

[Peter Maydell]

On 26 July 2013 16:41, Peter Maydell <address@hidden> wrote:
> These patches fix a couple of bugs in virtio-mmio's
> handling of the registers that deal with the queue size:
>
>  * as mst points out, letting the guest flip a queue between
>    "exists" and "doesn't exist" is a bad idea
>  * QueueNumMax wasn't reading the correct value for nonexistent
>    queues
>
> This doesn't include any change to the behaviour of queuesize
> on reset (discussed in other thread); the current behaviour is
> not a problem for well-behaved guests, and safe in the face
> of badly-behaved guests, and currently improving the reset
> behaviour is blocked by an unrelated bug.
>
> v1->v2: changes as per mst review:
>  * avoid explicit "== 0" comparisons
>  * avoid unnecessary parens round comparison ops
>  * do the "don't flip between existent and nonexistent" check
>    with "!!num != !!oldnum" (and add a comment noting why we're
>    doing this check)
>
> Peter Maydell (2):
>   hw/virtio/virtio: Don't allow guests to add/remove queues
>   hw/virtio/virtio-mmio: Make QueueNumMax read 0 for unavailable queues

These didn't make it into 1.6, but in the absence of any
review comments I'm putting them into arm-devs for post-1.6.

thanks
-- PMM