On Tue, May 22, 2018 at 06:26:15PM +0800, Tiwei Bie wrote:
> Allocate a feature bit for virtio devices which support SR-IOV.
>
> Suggested-by: Michael S. Tsirkin <[email protected]>
> Signed-off-by: Tiwei Bie <[email protected]>
> Fixes: https://github.com/oasis-tcs/virtio-spec/issues/11
> ---
> More details can be found from this thread:
> https://patchwork.kernel.org/patch/10285541/
>
> This patch needs below patch applied first:
> https://github.com/oasis-tcs/virtio-spec/issues/10
> https://lists.oasis-open.org/archives/virtio-dev/201805/msg00046.html
>
> v2 -> v3:
> - Improve the wording (Cornelia);
>
> v1 -> v2:
> - s/Reserve/Allocate/ (MST);
> - Add a Fixes tag (MST);
> - Be more explicit in driver requirement (MST);
> - Remove the "device MAY fail" description (MST);
> - Rebase on IO_BARRIER patch;
>
> RFC -> v1:
> - Mention PCI in the description (Cornelia);
>
> content.tex | 15 +++++++++++++--
> 1 file changed, 13 insertions(+), 2 deletions(-)
>
> diff --git a/content.tex b/content.tex
> index 95c243f..e9e6f9a 100644
> --- a/content.tex
> +++ b/content.tex
> @@ -95,10 +95,10 @@ Feature bits are allocated as follows:
> \begin{description}
> \item[0 to 23] Feature bits for the specific device type
>
> -\item[24 to 36] Feature bits reserved for extensions to the queue and
> +\item[24 to 37] Feature bits reserved for extensions to the queue and
> feature negotiation mechanisms
>
> -\item[37 and above] Feature bits reserved for future extensions.
> +\item[38 and above] Feature bits reserved for future extensions.
> \end{description}
>
> \begin{note}
> @@ -5357,6 +5357,9 @@ Descriptors} and \ref{sec:Packed Virtqueues / Indirect
> Flag: Scatter-Gather Supp
> better performance. This feature indicates whether
> a stronger form of barrier suitable for hardware
> devices is necessary.
> + \item[VIRTIO_F_SR_IOV(37)] This feature indicates that
> + the device supports Single Root I/O Virtualization.
> + Currently only PCI devices support this feature.
I guess the assumption is that all VFs and the PF are of the same type?
I feel it might be handy down the road to support mixing
types. For this reason, to avoid binding a wrong driver
to a VF, I propose that all VFs have this bit too,
and require that drivers ignore VFs without this bit.
What do you think?
> \end{description}
>
> \drivernormative{\section}{Reserved Feature Bits}{Reserved Feature Bits}
> @@ -5376,6 +5379,11 @@ A driver SHOULD accept VIRTIO_F_IO_BARRIER if it is
> offered.
> If VIRTIO_F_IO_BARRIER has been negotiated, a driver MUST use
> the barriers suitable for hardware devices.
>
> +A driver SHOULD accept VIRTIO_F_SR_IOV if it is offered.
> +If VIRTIO_F_SR_IOV has been negotiated, a driver can
> +enable virtual functions through the device's PCI SR-IOV
> +capability structure.
I feel the last sentence isn't clear enough. How about
a driver MUST negotiate VIRTIO_F_SR_IOV and complete the feature
negotiation (including setting the DRIVER_OK \field{status} bit) before
enabling virtual functions through the device's PCI SR-IOV capability
structure.
> +
> \devicenormative{\section}{Reserved Feature Bits}{Reserved Feature Bits}
>
> A device MUST offer VIRTIO_F_VERSION_1. A device MAY fail to operate further
> @@ -5392,6 +5400,9 @@ buffers in the same order in which they have been
> available.
> A device MAY fail to operate further if VIRTIO_F_IO_BARRIER
> is not accepted.
>
> +A device SHOULD offer VIRTIO_F_SR_IOV if it presents a PCI
> +SR-IOV capability structure.
> +
> \section{Legacy Interface: Reserved Feature Bits}\label{sec:Reserved Feature
> Bits / Legacy Interface: Reserved Feature Bits}
>
> Transitional devices MAY offer the following:
> --
> 2.17.0
>
>
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