Re: [PATCH v3 4/4] vhost-user: update shared memory capability

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Nikos Dragazis (ndragazis@arrikto.com) wrote:
> The virtio vhost-user device has shared memory resources. Therefore, it
> uses the VIRTIO_PCI_CAP_SHARED_MEMORY_CFG capability to standardize
> those resources through the PCI Configuration Space. This patch
> synchronizes the virtio vhost-user device spec with the following shared
> memory resources PATCH:
> 
> https://lists.oasis-open.org/archives/virtio-dev/201902/msg00142.html
> 
> Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
> Signed-off-by: Nikos Dragazis <ndragazis@arrikto.com>
> ---
>  virtio-vhost-user.tex | 17 ++++++++++++++++-
>  1 file changed, 16 insertions(+), 1 deletion(-)
> 
> diff --git a/virtio-vhost-user.tex b/virtio-vhost-user.tex
> index 7a8cd9c..d1305dd 100644
> --- a/virtio-vhost-user.tex
> +++ b/virtio-vhost-user.tex
> @@ -320,7 +320,22 @@ \subsubsection{Notification structure layout}\label{sec:Device Types / Vhost-use
>  \subsubsection{Shared memory capability}\label{sec:Device Types / Vhost-user Device Backend / Additional Device Resources over PCI / Shared Memory capability}
>  
>  The shared memory location is found using the VIRTIO_PCI_CAP_SHARED_MEMORY_CFG
> -capability.
> +capability. Using the additional \field{offset_hi} and \field{length_hi}
> +fields following the SHARED_MEMORY_CFG capability structure, the shared
> +memory region's 64-bit BAR offset is calculated as follows:
> +
> +\begin{lstlisting}
> +        offset_hi << 32 + cap.offset
> +\end{lstlisting}
> +
> +and the shared memory region's 64-bit length is calculated as follows:
> +
> +\begin{lstlisting}
> +        length_hi << 32 + cap.length
> +\end{lstlisting}
> +
> +The \field{cap.offset} and \field{cap.length} fields are taken from the
> +SHARED_MEMORY_CFG capability structure.

Yes, or this could just reference the:
{sec:Virtio Transport Options / Virtio Over PCI Bus / PCI Device Layout / Shared memory capability}

section once it's merged.

Do you actually need to specify that it's found by PCI though?
Could you just define it as using Shared Memory Regions,
reference {sec:Basic Facilities of a Virtio Device / Shared Memory Regions}
and then it would be defined to work with PCI, MMIO or CCW if they
define the shared memory region support.

Dave


>  \devicenormative{\paragraph}{Shared Memory capability}{Device Types / Vhost-user Device Backend / Additional Device Resources over PCI / Shared Memory capability}
>  The device MUST present exactly one shared memory capability.
> -- 
> 2.7.4
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK