Re: [RFC 0/2] virtio-rng: add a control queue

[Stefan Hajnoczi]

On Thu, Jan 23, 2020 at 04:16:58PM +0100, Laurent Vivier wrote:
> The kernel needs sometime to be able to cancel an ongoing command.
> 
> For instance, if the virtio-rng device uses the egd backend
> and this backend doesn't provide data, the buffer provided by the
> kernel is kept as long as it is needed.
> 
> On the kernel side, a read blocks until the buffer returns from QEMU.
> 
> As the read is done with a mutex held, all the hw_random interface
> hangs and we cannot switch to another hw_random backend.
> 
> So this series adds a control queue to the virtio-rng device to allow
> to flush the virtio-rng input queue to release the kernel mutex and
> to allow to switch to another device.
> 
> The kernel side series can be found at:
> 
> https://github.com/vivier/linux/commits/virtio-rng-ctrl
> 
> Laurent Vivier (2):
>   virtio-rng: prepare the introduction of a control queue
>   virtio-rng: add a control queue
> 
>  hw/core/machine.c                           |  1 +
>  hw/virtio/trace-events                      |  6 ++
>  hw/virtio/virtio-rng.c                      | 99 ++++++++++++++++++---
>  include/hw/virtio/virtio-rng.h              |  5 +-
>  include/standard-headers/linux/virtio_rng.h | 14 +++
>  5 files changed, 111 insertions(+), 14 deletions(-)

Where can I find the VIRTIO specification for this new virtqueue?

Thanks,
Stefan

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