[Qemu-devel] FW: Are there any qemu emulated SR-IOV devices?

[Qemu-devel] FW: Are there any qemu emulated SR-IOV devices?

[mwoodpatrick]

I wanted to play around with SR-IOV using qemu and was wondering if there
are any qemu emulated SR-IOV devices I could experiment with?

If not I plan on creating one and would appreciate any pointers to documents
describing how to add an emulated device that supports more than 8 functions
and has ARI enabled

Regards

Mark

Re: [Qemu-devel] FW: Are there any qemu emulated SR-IOV devices?

[Kashyap Chamarthy]

[Sorry, I'm a bit late in responding, as I missed this e-mail.]

On Thu, Jun 08, 2017 at 07:35:52AM -0700, mwoodpatrick@gmail.com wrote:
> I wanted to play around with SR-IOV using qemu and was wondering if there
> are any qemu emulated SR-IOV devices I could experiment with?

Near as I know there isn't any existing emulated SR-IOV device in QEMU.
But yes, an emulated SR-IOV would also be useful for testing purposes
for projects like OpenStack, without having the need for real hardware.

> If not I plan on creating one and would appreciate any pointers to documents
> describing how to add an emulated device that supports more than 8 functions
> and has ARI enabled

I'm far from an expert on this area, but just wanted to point out that
there's some existing support for SR-IOV in QEMU, added via:

    [PATCH v6 0/4] pcie: Add support for Single Root I/O Virtualization --
    https://lists.nongnu.org/archive/html/qemu-devel/2015-10/msg05155.html

Knut Omang (Cced) who added the above support also had some notes here
on how to implement an SR-IOV capable device.:

    https://lists.nongnu.org/archive/html/qemu-devel/2015-10/msg05157.html
    -- pcie: Add some SR/IOV API documentation	in docs/pcie_sriov.txt

        "Add a small intro + minimal documentation for how to implement
        SR/IOV support for an emulated device.


[...]
 
-- 
/kashyap

Re: [Qemu-devel] FW: Are there any qemu emulated SR-IOV devices?

[Knut Omang]

On Thu, 2017-10-05 at 16:31 +0200, Kashyap Chamarthy wrote:
> [Sorry, I'm a bit late in responding, as I missed this e-mail.]
> 
> On Thu, Jun 08, 2017 at 07:35:52AM -0700, mwoodpatrick@gmail.com wrote:
> > I wanted to play around with SR-IOV using qemu and was wondering if there
> > are any qemu emulated SR-IOV devices I could experiment with?
> 
> Near as I know there isn't any existing emulated SR-IOV device in QEMU.
> But yes, an emulated SR-IOV would also be useful for testing purposes
> for projects like OpenStack, without having the need for real hardware.
> 
> > If not I plan on creating one and would appreciate any pointers to documents
> > describing how to add an emulated device that supports more than 8 functions
> > and has ARI enabled
> 
> I'm far from an expert on this area, but just wanted to point out that
> there's some existing support for SR-IOV in QEMU, added via:
> 
>     [PATCH v6 0/4] pcie: Add support for Single Root I/O Virtualization --
>     https://lists.nongnu.org/archive/html/qemu-devel/2015-10/msg05155.html
> 
> Knut Omang (Cced) who added the above support also had some notes here
> on how to implement an SR-IOV capable device.:
> 
>     https://lists.nongnu.org/archive/html/qemu-devel/2015-10/msg05157.html
>     -- pcie: Add some SR/IOV API documentation	in docs/pcie_sriov.txt
> 
>         "Add a small intro + minimal documentation for how to implement
>         SR/IOV support for an emulated device.
> 
> 
> [...]

These are not (yet) in QEMU but can still be found here:

https://github.com/knuto/qemu

I try to rebase them from time to time.
The reason why Michael has not accepted them (yet) is to my understanding the lack of
working example devices - correct me if I am wrong.

I did provide the igb device which works as a proof of concept of a device with 32 VFs and
use of stride and ARI in that the SR/IOV logic itself can be verified, but it is not a
working device, just a quick hack on the e1000 code to make it look like an igb with
SR/IOV support.

But as far as I know, several people have used the SR/IOV patches for their own device
models. 

We have a fairly elaborate and complex model (of an Infiniband HCA) that uses this, and
that has been used quite extensively, the problem is that the main part of the code
implementing the device is inside a simulation model outside of QEMU, just communicating 
PCIe transactions with QEMU over a TCP connection. So it is not that easy to make use of
inside QEMU. I do however want to pursue ways to provide the QEMU side of that
implementation to QEMU, as a tool for other device developers. If there are more people
interested in this domain, maybe we should have a BoF session about it at KVM Forum.

Thanks,
Knut