[virtio-dev] Re: [PATCH v3] content: document SR-IOV driver requirements

[Cornelia Huck <cohuck@redhat.com>]

On Tue, 12 Jun 2018 13:18:00 +0800
Tiwei Bie <tiwei.bie@intel.com> wrote:

> Document the driver requirements for the VIRTIO_F_SR_IOV
> feature bit.
> 
> Suggested-by: Michael S. Tsirkin <mst@redhat.com>
> Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
> Fixes: https://github.com/oasis-tcs/virtio-spec/issues/13
> ---
> v2:
> - Fix the commit message (MST);
> - Improve the wording (MST);
> - Drop unnecessary parts (MST);
> 
> v3:
> - status -> device status (MST);
> 
>  content.tex | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> diff --git a/content.tex b/content.tex
> index be18234..ab18210 100644
> --- a/content.tex
> +++ b/content.tex
> @@ -5387,6 +5387,21 @@ 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.
>  
> +If VIRTIO_F_SR_IOV has been negotiated, a driver MAY enable
> +virtual functions through the device's PCI SR-IOV capability
> +structure.  A driver MUST NOT negotiate VIRTIO_F_SR_IOV if
> +the device does not have a PCI SR-IOV capability structure
> +or is not a PCI device.  A driver MUST negotiate
> +VIRTIO_F_SR_IOV and complete the feature negotiation
> +(including checking the FEATURES_OK \field{device status}
> +bit) before enabling virtual functions through the device's
> +PCI SR-IOV capability structure.  After once successfully
> +negotiating VIRTIO_F_SR_IOV, the driver MAY enable virtual
> +functions through the device's PCI SR-IOV capability
> +structure even if the device or the system has been fully
> +or partially reset, and even without re-negotiating
> +VIRTIO_F_SR_IOV after the reset.
> +
>  \devicenormative{\section}{Reserved Feature Bits}{Reserved Feature Bits}
>  
>  A device MUST offer VIRTIO_F_VERSION_1.  A device MAY fail to operate further

I still think we should mention somewhere that this "enable just once"
mechanism is useful for e.g. resuming; but this is fine as-is.

Reviewed-by: Cornelia Huck <cohuck@redhat.com>

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