[virtio-comment] Re: [PATCH v5 4/5] shared memory: Define PCI capability

[Cornelia Huck <cohuck@redhat.com>]

On Thu, 27 Jun 2019 20:28:29 +0100
"Dr. David Alan Gilbert (git)" <dgilbert@redhat.com> wrote:

> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> 
> Define the PCI capability used for enumerating shared memory regions.
> 
> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> ---
>  content.tex | 20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
> 
> diff --git a/content.tex b/content.tex
> index 63e9179..fcf0d81 100644
> --- a/content.tex
> +++ b/content.tex
> @@ -689,6 +689,8 @@ \subsection{Virtio Structure PCI Capabilities}\label{sec:Virtio Transport Option
>  #define VIRTIO_PCI_CAP_DEVICE_CFG        4
>  /* PCI configuration access */
>  #define VIRTIO_PCI_CAP_PCI_CFG           5
> +/* Shared memory region */
> +#define VIRTIO_PCI_CAP_SHARED_MEMORY_CFG 8
>  \end{lstlisting}
>  
>          Any other value is reserved for future use.
> @@ -1075,6 +1077,24 @@ \subsubsection{Device-specific configuration}\label{sec:Virtio Transport Options
>  
>  The \field{offset} for the device-specific configuration MUST be 4-byte aligned.
>  
> +\subsubsection{Shared memory capability}\label{sec:Virtio Transport Options / Virtio Over PCI Bus / PCI Device Layout / Shared memory capability}
> +
> +Shared memory regions \ref{sec:Basic Facilities of a Virtio
> +Device / Shared Memory Regions} are enumerated on the PCI transport
> +as a sequence of VIRTIO_PCI_CAP_SHARED_MEMORY_CFG capabilities, one per region.
> +
> +The capability is defined by a struct virtio_pci_cap64 and
> +utilises the \field{cap.id} to allow multiple shared memory
> +regions per device.

Maybe add a sentence here

"The identifier in \field{cap.id} does not denote a certain order of
preference; it is only used to uniquely identify a region."

(as per discussion of patch 2)

> +
> +\devicenormative{\paragraph}{Device-specific configuration}{Virtio Transport Options / Virtio Over PCI Bus / PCI Device Layout / Shared memory capability}
> +
> +The region defined by the combination of the \field {cap.offset},
> +\field {cap.offset_hi}, and \field {cap.length}, \field
> +{cap.length_hi} fields MUST be contained within the declared bar.
> +
> +The \field{cap.id} MUST be unique for any one device instance.
> +
>  \subsubsection{PCI configuration access capability}\label{sec:Virtio Transport Options / Virtio Over PCI Bus / PCI Device Layout / PCI configuration access capability}
>  
>  The VIRTIO_PCI_CAP_PCI_CFG capability

Else, looks good to me.

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