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Subject: Re: [virtio-dev] [PATCH v3] content: support SR-IOV
On Wed, May 23, 2018 at 08:54:47PM +0300, Michael S. Tsirkin wrote: > 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 <mst@redhat.com> > > Signed-off-by: Tiwei Bie <tiwei.bie@intel.com> > > 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? Thinking more about it, I can see how this might interfere with passing VFs through to legacy nested guests. How about reversing it then? Require that drivers MUST NOT negotiate VIRTIO_F_SR_IOV if device does not have an SRIOV capability or is not a PCI device, in particular a VF. And say a device without SRIOV cap SHOULD NOT expose this bit. > > \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 > > > > > > --------------------------------------------------------------------- > > To unsubscribe, e-mail: virtio-dev-unsubscribe@lists.oasis-open.org > > For additional commands, e-mail: virtio-dev-help@lists.oasis-open.org
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