[virtio-dev] [PATCH v3] content: support SR-IOV

[virtio-dev] [PATCH v3] content: support SR-IOV

[Tiwei Bie]

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.
 \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.
+
 \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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[virtio-dev] Re: [PATCH v3] content: support SR-IOV

[Cornelia Huck]

On Tue, 22 May 2018 18:26:15 +0800
Tiwei Bie <tiwei.bie@intel.com> 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

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

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Re: [virtio-dev] [PATCH v3] content: support SR-IOV

[Michael S. Tsirkin]

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?

>  \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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Re: [virtio-dev] [PATCH v3] content: support SR-IOV

[Michael S. Tsirkin]

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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Re: [virtio-dev] [PATCH v3] content: support SR-IOV

[Tiwei Bie]

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 <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.

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. 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.
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 a PCI SR-IOV
capability structure.

> 
> 
> > >  \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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Re: [virtio-dev] [PATCH v3] content: support SR-IOV

[Michael S. Tsirkin]

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 <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.
> 
> 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.

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.



> 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

> 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.

> > 
> > 
> > > >  \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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Re: [virtio-dev] [PATCH v3] content: support SR-IOV

[Tiwei Bie]

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 <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.
> > 
> > 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
> 

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Re: [virtio-dev] [PATCH v3] content: support SR-IOV

[Michael S. Tsirkin]

On Thu, May 24, 2018 at 11:15:26PM +0800, Tiwei Bie wrote:
> 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 <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.
> > > 
> > > 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.

Sounds good.

> 
> > 
> > 
> > 
> > > 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

Sounds good.

> > 
> > > > 
> > > > 
> > > > > >  \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
> > 

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Re: [virtio-dev] [PATCH v3] content: support SR-IOV

[Tiwei Bie]

On Thu, May 24, 2018 at 06:20:36PM +0300, Michael S. Tsirkin wrote:
> On Thu, May 24, 2018 at 11:15:26PM +0800, Tiwei Bie wrote:
> > 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:
[...]
> > > 
> > > 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.
> 
> Sounds good.
> 
[...]
> > > 
> > > 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
> 
> Sounds good.

Thanks a lot! I'll send a new version.

Best regards,
Tiwei Bie

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