From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: virtio-dev-return-4165-cohuck=redhat.com@lists.oasis-open.org Sender: List-Post: List-Help: List-Unsubscribe: List-Subscribe: Received: from lists.oasis-open.org (oasis-open.org [66.179.20.138]) by lists.oasis-open.org (Postfix) with ESMTP id 0961E5818DFE for ; Thu, 24 May 2018 08:15:25 -0700 (PDT) Date: Thu, 24 May 2018 23:15:26 +0800 From: Tiwei Bie Message-ID: <20180524151526.GB26913@debian> References: <20180522102615.21339-1-tiwei.bie@intel.com> <20180523204446-mutt-send-email-mst@kernel.org> <20180523223204-mutt-send-email-mst@kernel.org> <20180524000641.GA23755@debian> <20180524163054-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20180524163054-mutt-send-email-mst@kernel.org> Subject: Re: [virtio-dev] [PATCH v3] content: support SR-IOV To: "Michael S. Tsirkin" Cc: cohuck@redhat.com, stefanha@redhat.com, pbonzini@redhat.com, virtio-dev@lists.oasis-open.org, dan.daly@intel.com, alexander.h.duyck@intel.com, mark.d.rustad@intel.com, cunming.liang@intel.com, zhihong.wang@intel.com List-ID: On Thu, May 24, 2018 at 04:44:18PM +0300, Michael S. Tsirkin wrote: > On Thu, May 24, 2018 at 08:06:41AM +0800, Tiwei Bie wrote: > > On Wed, May 23, 2018 at 10:34:29PM +0300, Michael S. Tsirkin wrote: > > > 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 > > > > > Signed-off-by: Tiwei Bie > > > > > 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. > > > > I think driver can accept this feature as long as it's > > able to handle the SR-IOV capability and there is no > > need for it to check whether the device has the SR-IOV > > capability. > > So my point is this, VFs themselves do not have > this feature. Yeah. I also think VFs shouldn't present this feature. > > Should all of them have it? None of them? > I don't see what use it is to VFs, but maybe > we will come with a use down the road. > > I propose we require that > 1. drivers ignore this if there is > no SRIOV cap, and > > 2. that devices do not expose it. > > This way if we come up with a use down the road, only new drivers > will negotiate it. I got your point now. Thanks! How about: If VIRTIO_F_SR_IOV has been negotiated, a driver can 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 setting the DRIVER_OK \field{status} bit) before enabling virtual functions through the device's PCI SR-IOV capability structure. > > > > > And device should make sure that it won't > > offer this feature if it doesn't present this capability. > > How about changing the driver requirement to: > > > > A driver SHOULD accept VIRTIO_F_SR_IOV if it is offered. > > This part won't address the issue above. > > > > If VIRTIO_F_SR_IOV has been negotiated, a driver can > > enable virtual functions through the device's PCI SR-IOV > > capability structure. 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. > > > > > > > > > > And say a device without SRIOV cap SHOULD NOT expose this bit. > > > > > > > No problem. How about: > > > > A device SHOULD offer VIRTIO_F_SR_IOV if it presents a > > PCI SR-IOV capability structure. A device SHOULD NOT > > offer VIRTIO_F_SR_IOV if it doesn't presents > > doesn't present Right. Thanks for catching it! > > > a PCI SR-IOV > > capability structure. > > Assuming we teach drivers they should ignore it > if it is there without SRIOV, then this last one I'd make MUST NOT. Okay, how about A device SHOULD offer VIRTIO_F_SR_IOV if it is a PCI device and presents a PCI SR-IOV capability structure, otherwise it MUST NOT offer VIRTIO_F_SR_IOV. Best regards, Tiwei Bie > > > > > > > > > > > > \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 > > --------------------------------------------------------------------- > To unsubscribe, e-mail: virtio-dev-unsubscribe@lists.oasis-open.org > For additional commands, e-mail: virtio-dev-help@lists.oasis-open.org > --------------------------------------------------------------------- To unsubscribe, e-mail: virtio-dev-unsubscribe@lists.oasis-open.org For additional commands, e-mail: virtio-dev-help@lists.oasis-open.org