Re: [PATCH V2 4/6] virtio-pci: implement VIRTIO_F_QUEUE_STATE

["Zhu, Lingshan" <lingshan.zhu@intel.com>]

On 11/3/2023 7:35 PM, Parav Pandit wrote:
> > From: Zhu Lingshan <lingshan.zhu@intel.com>
> > Sent: Friday, November 3, 2023 4:05 PM
> >
> > This patch adds two new le16 fields to common configuration structure to
> > support VIRTIO_F_QUEUE_STATE in PCI transport layer.
> >
> > Signed-off-by: Zhu Lingshan <lingshan.zhu@intel.com>
> > ---
> >   transport-pci.tex | 18 ++++++++++++++++++
> >   1 file changed, 18 insertions(+)
> >
> > diff --git a/transport-pci.tex b/transport-pci.tex index a5c6719..3161519 100644
> > --- a/transport-pci.tex
> > +++ b/transport-pci.tex
> > @@ -325,6 +325,10 @@ \subsubsection{Common configuration structure
> > layout}\label{sec:Virtio Transport
> >           /* About the administration virtqueue. */
> >           le16 admin_queue_index;         /* read-only for driver */
> >           le16 admin_queue_num;         /* read-only for driver */
> > +
> > +	/* Virtqueue state */
> > +        le16 queue_avail_state;         /* read-write */
> > +        le16 queue_used_state;          /* read-write */
> This tiny interface for 128 virtio net queues through register read writes, does not work effectively.
> There are inflight out of order descriptors for block also.
> Hence toy registers like this do not work.
Do you know there is a queue_select? Why this does not work? Do you know 
how other queue related fields work?
Like how to set a queue size and enable it?
> Series [1] is comprehensive that covers it even if you consider non-passtrhough device migration model.
> Where you can suspend individual queues using new admin command and get them in the device context state.
>
> [1] https://lists.oasis-open.org/archives/virtio-comment/202310/msg00472.html
I suggest you read QEMU migration code. If you don't want to, not my fault.
> >   };
> >   \end{lstlisting}
> >
> > @@ -428,6 +432,17 @@ \subsubsection{Common configuration structure
> > layout}\label{sec:Virtio Transport
> >   	The value 0 indicates no supported administration virtqueues.
> >   	This field is valid only if VIRTIO_F_ADMIN_VQ has been
> >   	negotiated.
> > +
> > +\item[\field{queue_avail_state}]
> > +        This field is valid only if VIRTIO_F_QUEUE_STATE has been
> > +        negotiated. The driver sets and gets the available state of
> > +        the virtqueue here (see \ref{sec:Virtqueues / Virtqueue State}).
> > +
> > +\item[\field{queue_used_state}]
> > +        This field is valid only if VIRTIO_F_QUEUE_STATE has been
> > +        negotiated. The driver sets and gets the used state of the
> > +        virtqueue here (see \ref{sec:Virtqueues / Virtqueue State}).
> > +
> >   \end{description}
> >
> >   \devicenormative{\paragraph}{Common configuration structure layout}{Virtio
> > Transport Options / Virtio Over PCI Bus / PCI Device Layout / Common
> > configuration structure layout} @@ -488,6 +503,9 @@ \subsubsection{Common
> > configuration structure layout}\label{sec:Virtio Transport  present either a value
> > of 0 or a power of 2 in  \field{queue_size}.
> >
> > +If VIRTIO_F_QUEUE_STATE has not been negotiated, the device MUST ignore
> > +any accesses to \field{queue_avail_state} and \field{queue_used_state}.
> > +
> >   If VIRTIO_F_ADMIN_VQ has been negotiated, the value
> > \field{admin_queue_index} MUST be equal to, or bigger than
> > \field{num_queues}; also, \field{admin_queue_num} MUST be
> > --
> > 2.35.3