On Wed, Mar 20, 2019 at 12:07:39PM +0000, Dr. David Alan Gilbert (git) wrote:
> From: "Dr. David Alan Gilbert" <>
>
> Define the PCI capability used for enumerating shared memory regions.
>
> Signed-off-by: Dr. David Alan Gilbert <>
> Reviewed-by: Stefan Hajnoczi <>
> Reviewed-by: Cornelia Huck <>
> ---
> content.tex | 37 +++++++++++++++++++++++++++++++++++++
> 1 file changed, 37 insertions(+)
>
> diff --git a/content.tex b/content.tex
> index 8cd1a38..ddbf949 100644
> --- a/content.tex
> +++ b/content.tex
> @@ -688,6 +688,8 @@ The fields are interpreted as follows:
> #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.
> @@ -1052,6 +1054,41 @@ any device type which has a device-specific configuration.
>
> 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 immediately followed by an additional field like so:
> +
> +\begin{lstlisting}
> +struct virtio_pci_shm_cap {
> + struct virtio_pci_cap cap;
> + u32 offset_hi;
> + u32 length_hi;
> + u8 id;
Pls pad, pci capabilities must be a multiple of 4 bytes.
BTW virtio_pci_cap has 3 bytes of padding.
We can stick the id there maybe?
> +};
> +\end{lstlisting}
> +
> +Given that the \field{cap.length} and \field{cap.offset} fields
> +are only 32 bit, the additional \field{offset_hi} and \field {length_hi}
> +fields provide the most significant 32 bits of a total 64 bit offset and
> +length within the bar specified by \field{cap.bar}. \field{id}
> +uniquely identifies the given shared memory region using a device
> +specific identifier.
I didn't realize we will ever need so much space. I think I prefer
moving offset_hi/length_hi to a general virtio_pci_cap64 that others can
reuse.
> +
> +While most capabilities can not be repeated,
I'd drop this part.
> multiple
> +VIRTIO_PCI_CAP_SHARED_MEMORY_CFG capabilities are allowed as long
> +as the \field{id} is unique.
> +
> +\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 offsets and length
> +fields
let's do \field{cap.length} \field{cap.offset} etc.
>MUST be contained within the declared bar.
> +
> +The \field{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
> --
> 2.20.1
>
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail:
> For additional commands, e-mail:
