Re: [PATCH v3] virtio-rng: add a control queue

[Cornelia Huck <cohuck@redhat.com>]

On Tue,  4 Aug 2020 17:41:27 +0200
Laurent Vivier <lvivier@redhat.com> wrote:

> A control queue is needed to send command to ask the device to
> release the request buffers if it cannot provide data.
> 
> Changes:
> 
>   5.4.2 Virtqueues
>   0 requestq
>   1 controlq
>   controlq only exists if VIRTIO_RNG_F_CTRL_VQ set.
> 
>   5.4.3 Feature bits
>   VIRTIO_RNG_F_CTRL_VQ (0)
>   Device has a control queue
> 
>   5.4.5 Device Initialization
>   Identify and initialize the request virtqueue.
>   If the VIRTIO_RNG_F_CTRL_VQ feature bit is negotiated,
>   identify the control virtqueue.
> 
>   5.4.6.3 Control Virtqueue
>   The driver uses the control virtqueue (if VIRTIO_RNG_F_CTRL_VQ is
>   negotiated) to send commands to control the device.
>   All commands are of the following form:
>   struct virtio_rng_ctrl_hdr {
>          u8 cmd;
>   };
> 
>   5.4.6.4 Device Requirements: Control Virtqueue
>   If VIRTIO_RNG_F_CTRL_VQ is negotiated, the device MUST implement the
>   flush command.
>   Any other value of cmd MUST be ignored by the device.
> 
>   5.4.6.5 Request Virtqueue Flushing
>   When the device is not able to provide enough entropy to the driver, the
>   driver may be stuck waiting for the device returning buffers, and cannot
>   be removed to switch to another one. The flush command allows the driver
>   to ask the device to release all the buffers sent to the device. This
>   allows the driver to release resources allocated to receive data from
>   the device.
>   #define VIRTIO_RNG_CMD_FLUSH 0
> 
>   5.4.6.5.1 Device Requirements: Request Virtqueue Flushing
>   When the driver sends a flush request, the device MUST release all
>   outstanding buffers.
> 
> Bug-Link: https://github.com/oasis-tcs/virtio-spec/issues/83
> Signed-off-by: Laurent Vivier <lvivier@redhat.com>
> ---
> 
> Notes:
>     v3: Add devicenormative references in conformance part
>         Move "Request Virtqueue Flushing" from \paragraph to \subsubsection
>         to be behind "Control Virtqueue" and not behind
>         "Device Requirements: Control Virtqueue"

There are different ways to put the conformance statements (and what
should be a paragraph vs a subsubsection), and your layout seems
reasonable, avoiding nesting too deep.

>     
>     v2: Add devicenormative for the Control Virtqueue
>         Add devicenormative for the Request Virtqueue Flushing
>         Reword paragraph Request Virtqueue Flushing
> 
>  conformance.tex |  2 ++
>  content.tex     | 47 +++++++++++++++++++++++++++++++++++++++++++++--
>  2 files changed, 47 insertions(+), 2 deletions(-)

Reviewed-by: Cornelia Huck <cohuck@redhat.com>