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

[Stefan Hajnoczi <stefanha@redhat.com>]

On Tue, Apr 23, 2019 at 06:18:19PM +0300, Nikos Dragazis 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
> 
> Signed-off-by: Nikos Dragazis <ndragazis@arrikto.com>
> ---
>  virtio-vhost-user.tex | 17 ++++++++++++++++-
>  1 file changed, 16 insertions(+), 1 deletion(-)

CCing David Gilbert, author of the shared memory resource spec.

> diff --git a/virtio-vhost-user.tex b/virtio-vhost-user.tex
> index 605272f..4a2fee3 100644
> --- a/virtio-vhost-user.tex
> +++ b/virtio-vhost-user.tex
> @@ -318,7 +318,22 @@ \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.
>  
>  \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
> 
> 
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