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Subject: Re: [virtio-dev] [RFC] content: support SR-IOV
On Fri, 18 May 2018 16:43:09 +0800 Tiwei Bie <tiwei.bie@intel.com> wrote: > On Fri, May 18, 2018 at 10:14:38AM +0200, Cornelia Huck wrote: > > On Fri, 18 May 2018 15:38:55 +0800 > > Tiwei Bie <tiwei.bie@intel.com> wrote: > > > > > Reserve a feature bit for virtio devices which support SR-IOV. > > > > Reserving a feature bit for this makes sense, but... > > > > > > > > Suggested-by: Michael S. Tsirkin <mst@redhat.com> > > > Signed-off-by: Tiwei Bie <tiwei.bie@intel.com> > > > --- > > > More details can be found from this thread: > > > https://patchwork.kernel.org/patch/10285541/ > > > > > > content.tex | 14 ++++++++++++-- > > > 1 file changed, 12 insertions(+), 2 deletions(-) > > > > > > diff --git a/content.tex b/content.tex > > > index 7a92cb1..62214fa 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 33] Feature bits reserved for extensions to the queue and > > > +\item[24 to 36] Feature bits reserved for extensions to the queue and > > > feature negotiation mechanisms > > > > > > -\item[34 and above] Feature bits reserved for future extensions. > > > +\item[37 and above] Feature bits reserved for future extensions. > > > \end{description} > > > > > > \begin{note} > > > @@ -5348,6 +5348,8 @@ Descriptors} and \ref{sec:Packed Virtqueues / Indirect Flag: Scatter-Gather Supp > > > \item[VIRTIO_F_IN_ORDER(35)] This feature indicates > > > that all buffers are used by the device in the same > > > order in which they have been made available. > > > + \item[VIRTIO_F_SR_IOV(36)] This feature indicates that > > > + the device supports Single Root I/O Virtualization. > > > > ...shouldn't this mention 'PCI' somewhere? This feature does not make > > sense on any transport but PCI. > > Yeah. When Michael suggested this feature, he also said: > > https://patchwork.kernel.org/patch/10285541/ > """ > It seems PCI specific so non pci transports would disable the feature > for now. > """ > > Based on the current description, transports other than > PCI would have this feature bit disabled. > > Do you think there is any possibility that other transports > may reuse this feature bit to do something similar? I don't know about mmio (and I'm not sure how actively it is developed), but ccw is so different that I don't see how it could match to anything there. > > Or do you think we should make this feature bit PCI specific > and don't leave any chance for other transports to reuse > it, e.g. by naming it as VIRTIO_F_PCI_SR_IOV? > > Or do you think it's OK to still name it as VIRTIO_F_SR_IOV, > but add the word 'PCI' when talking about the capability, > e.g.: > > A device SHOULD offer VIRTIO_F_SR_IOV if it presents a PCI > SR-IOV capability structure. A device MAY fail to operate > further if VIRTIO_F_SR_IOV is not accepted. Adding 'PCI' to the description is probably best, I think.
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