Re: [virtio-dev] [PATCH RESEND] virtio-pmem: PMEM device spec

[Pankaj Gupta <pankaj.gupta.linux@gmail.com>]

> > On 04.08.21 13:07, Stefan Hajnoczi wrote:
> > > On Wed, Jul 28, 2021 at 05:04:35PM +0200, Pankaj Gupta wrote:
> > > > +\subsection{Device configuration layout}\label{sec:Device Types / PMEM Device / Device configuration layout}
> > > > +
> > > > +\begin{lstlisting}
> > > > +struct virtio_pmem_config {
> > > > + le64 start;
> > > > + le64 size;
> > > > +};
> > > > +\end{lstlisting}
> > > > +
> > > > +\begin{description}
> > > > +\item[\field{start}] contains the start address from the guest physical address range
> > > > +to be hotplugged into the guest address space using the pmem API.
> > > > +
> > > > +\item[\field{size}] contains the length of this address range.
> > > > +\end{description}
> > >
> > > Please use a Shared Memory Region instead. This is a relatively new
> > > addition to the VIRTIO device model that seems like a good fit for this
> > > device:
> > > https://github.com/oasis-tcs/virtio-spec/blob/master/shared-mem.tex
> >
> > Note that virtio-pmem is already upstream in QEMU and in Linux using this
> > model. There is a proposal to optionally use shared memory for exposing the
> > area, to be unlocked with a feature bit.
>
> Please incorporate the proposal into this patch. A feature bit is a good
> way of handling this case.

You mean in the patch with parent spec?

>
> Although the difference between configuration space parameters and a
> shared memory region might seem trivial, I think using the shared memory
> region is worthwhile because it makes the memory region a first-class
> concept in the VIRTIO device model that is supported by the driver and
> device emulation infrastructure.
>
> Stefan