Re: [PATCH] virtio-mmio: Clear v2 transport state on soft reset

[Sergio Lopez <slp@redhat.com>]

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Jean-Philippe Brucker <jean-philippe@linaro.org> writes:

> At the moment when the guest writes a status of 0, we only reset the
> virtio core state but not the virtio-mmio state. The virtio-mmio
> specification says (v1.1 cs01, 4.2.2.1 Device Requirements:
> MMIO Device Register Layout):
>
>     Upon reset, the device MUST clear all bits in InterruptStatus and
>     ready bits in the QueueReady register for all queues in the device.
>
> The core already takes care of InterruptStatus by clearing isr, but we
> still need to clear QueueReady.
>
> It would be tempting to clean all registers, but since the specification
> doesn't say anything more, guests could rely on the registers keeping
> their state across reset. Linux for example, relies on this for
> GuestPageSize in the legacy MMIO tranport.
>
> Fixes: 44e687a4d9ab ("virtio-mmio: implement modern (v2) personality (virtio-1)")
> Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
> ---
> This fixes kexec of a Linux guest that uses the modern virtio-mmio
> transport.
> ---
>  hw/virtio/virtio-mmio.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)

LGTM, thanks!

Reviewed-by: Sergio Lopez <slp@redhat.com>

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