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Re: [Qemu-devel] [PATCH virtio 1/1] Add "Group Identifier" support to vi
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] [PATCH virtio 1/1] Add "Group Identifier" support to virtio PCI capabilities. |
Date: |
Tue, 19 Jun 2018 20:30:06 +0300 |
On Tue, Jun 19, 2018 at 11:32:28AM -0500, Venu Busireddy wrote:
> Add VIRTIO_PCI_CAP_GROUP_ID_CFG (Group Identifier) capability to the
> virtio PCI capabilities to allow for the grouping of devices.
>
> Signed-off-by: Venu Busireddy <address@hidden>
> ---
> content.tex | 43 +++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 43 insertions(+)
>
> diff --git a/content.tex b/content.tex
> index 7a92cb1..7ea6267 100644
> --- a/content.tex
> +++ b/content.tex
> @@ -599,6 +599,8 @@ The fields are interpreted as follows:
> #define VIRTIO_PCI_CAP_DEVICE_CFG 4
> /* PCI configuration access */
> #define VIRTIO_PCI_CAP_PCI_CFG 5
> +/* Group Identifier */
> +#define VIRTIO_PCI_CAP_GROUP_ID_CFG 6
> \end{lstlisting}
>
> Any other value is reserved for future use.
> @@ -997,6 +999,47 @@ address \field{cap.length} bytes within a BAR range
> specified by some other Virtio Structure PCI Capability
> of type other than \field{VIRTIO_PCI_CAP_PCI_CFG}.
>
> +\subsubsection{Group Identifier capability}\label{sec:Virtio Transport
> Options / Virtio Over PCI Bus / PCI Device Layout / Group Identifier
> capability}
> +
> +The VIRTIO_PCI_CAP_GROUP_ID_CFG capability provides means for grouping
> devices together.
> +
> +The capability is immediately followed by an identifier of arbitrary size as
> below:
> +
> +\begin{lstlisting}
> +struct virtio_pci_group_id_cap {
> + struct virtio_pci_cap cap;
> + u8 group_id[]; /* Group Identifier */
> +};
> +\end{lstlisting}
> +
> +The fields \field{cap.bar}, \field{cap.length}, \field{cap.offset}
> +and \field{group_id} are read-only for the driver.
> +
> +The specification does not impose any restrictions on the size or
> +structure of group_id[].
I think it must be a multiple of 4 in size, as is
standard for all capabilities.
> Vendors are free to declare this array as
> +large as needed, as long as the combined size of all capabilities can
> +be accommodated within the PCI configuration space.
> +
> +If there is enough room in the PCI configuration space to accommodate
> +the group identifier, the fields \field{cap.bar}, \field{cap.offset}
> +and \field{cap.length} should be set to 0.
> +
> +If there isn't enough room, some or all of the group identifier can be
> +presented in the BAR region, in which case the fields \field{cap.bar},
> +\field{cap.offset} and \field{cap.length} should be set appropriately.
And then how do you glue the two pieces?
> +
> +In either case, the field \field{cap.cap_len} indicates the length of
> +the group identifier information present in the configuration space
> +itself.
It seems like an overkill to me. Isn't it enough to have it in config
space? This would make comparisons easier.
> +
> +\devicenormative{\paragraph}{Group Identifier capability}{Virtio Transport
> Options / Virtio Over PCI Bus / PCI Device Layout / Group Identifier
> capability}
> +
> +The device MAY present the VIRTIO_PCI_CAP_GROUP_ID_CFG capability.
> +
> +\drivernormative{\paragraph}{Group Identifier capability}{Virtio Transport
> Options / Virtio Over PCI Bus / PCI Device Layout / Group Identifier
> capability}
> +
> +The driver MUST NOT write to group_id[] area or the BAR region.
> +
> \subsubsection{Legacy Interfaces: A Note on PCI Device
> Layout}\label{sec:Virtio Transport Options / Virtio Over PCI Bus / PCI Device
> Layout / Legacy Interfaces: A Note on PCI Device Layout}
>
> Transitional devices MUST present part of configuration
- Re: [Qemu-devel] [PATCH 2/3] Add "Group Identifier" support to PCIe bridges., (continued)
- Re: [Qemu-devel] [PATCH 2/3] Add "Group Identifier" support to PCIe bridges., Michael S. Tsirkin, 2018/06/19
- Re: [Qemu-devel] [virtio-dev] Re: [PATCH 2/3] Add "Group Identifier" support to PCIe bridges., Venu Busireddy, 2018/06/19
- Re: [Qemu-devel] [virtio-dev] Re: [PATCH 2/3] Add "Group Identifier" support to PCIe bridges., Michael S. Tsirkin, 2018/06/19
- Re: [Qemu-devel] [virtio-dev] Re: [PATCH 2/3] Add "Group Identifier" support to PCIe bridges., Venu Busireddy, 2018/06/19
- Re: [Qemu-devel] [virtio-dev] Re: [PATCH 2/3] Add "Group Identifier" support to PCIe bridges., Michael S. Tsirkin, 2018/06/19
- Re: [Qemu-devel] [virtio-dev] Re: [PATCH 2/3] Add "Group Identifier" support to PCIe bridges., Venu Busireddy, 2018/06/19
- Re: [Qemu-devel] [virtio-dev] Re: [PATCH 2/3] Add "Group Identifier" support to PCIe bridges., Michael S. Tsirkin, 2018/06/19
[Qemu-devel] [PATCH 3/3] Add "Group Identifier" support to virtio devices., Venu Busireddy, 2018/06/19
[Qemu-devel] [PATCH 1/3] Add a true or false option to the DEFINE_PROP_UUID macro., Venu Busireddy, 2018/06/19
[Qemu-devel] [PATCH virtio 1/1] Add "Group Identifier" support to virtio PCI capabilities., Venu Busireddy, 2018/06/19
- Re: [Qemu-devel] [PATCH virtio 1/1] Add "Group Identifier" support to virtio PCI capabilities.,
Michael S. Tsirkin <=