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

[Stefan Hajnoczi <stefanha@redhat.com>]

On Wed, Aug 04, 2021 at 01:11:52PM +0200, David Hildenbrand wrote:
> 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.

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

Attachment: signature.asc
Description: PGP signature