Regarding VIRTIO_F_IN_ORDER and VIRTIO_F_NOTIFICATION_DATA feature bits

Regarding VIRTIO_F_IN_ORDER and VIRTIO_F_NOTIFICATION_DATA feature bits

[Srujana Challa]

Hi Michael,

While verifying virtio frontend drivers of guest OS on qemu with vhost-vdpa backend,
we came across feature bits VIRTIO_F_IN_ORDER and VIRTIO_F_NOTIFICATION_DATA,
which are introduced in virtio 1.1 spec, are not yet enabled in qemu. These feature flags
are very much useful for achieving better virtio-net performance and most of the latest
hardware VDPA devices supports these feature flags as per of virtio spec.
Could you let us know if there are any plans, to add support for these features in upcoming
qemu releases.
I guess there was some discussion on VIRTIO_F_IN_ORDER feature bit long ago,
https://patchew.org/QEMU/1533833677-27512-1-git-send-email-i.maximets@samsung.com/
Seems like that discussion has not reached any conclusion or further work.

Thanks,
Srujana.

Re: Regarding VIRTIO_F_IN_ORDER and VIRTIO_F_NOTIFICATION_DATA feature bits

[Michael S. Tsirkin]

On Wed, Dec 13, 2023 at 04:27:40PM +0000, Srujana Challa wrote:
> Hi Michael,
> 
> While verifying virtio frontend drivers of guest OS on qemu with vhost-vdpa backend,
> we came across feature bits VIRTIO_F_IN_ORDER and VIRTIO_F_NOTIFICATION_DATA,
> which are introduced in virtio 1.1 spec, are not yet enabled in qemu. These feature flags
> are very much useful for achieving better virtio-net performance and most of the latest
> hardware VDPA devices supports these feature flags as per of virtio spec.

Could you share more about which device do you mean? Does Marvell ship
or intends to ship one?

> Could you let us know if there are any plans, to add support for these features in upcoming
> qemu releases.
> I guess there was some discussion on VIRTIO_F_IN_ORDER feature bit long ago,
> https://patchew.org/QEMU/1533833677-27512-1-git-send-email-i.maximets@samsung.com/
> Seems like that discussion has not reached any conclusion or further work.
> 
> Thanks,
> Srujana.

Yes that patch got comments and these were not addressed.
Feel free to address them so this can proceed.

-- 
MST

RE: [EXT] Re: Regarding VIRTIO_F_IN_ORDER and VIRTIO_F_NOTIFICATION_DATA feature bits

[Srujana Challa]

> ----------------------------------------------------------------------
> On Wed, Dec 13, 2023 at 04:27:40PM +0000, Srujana Challa wrote:
> > Hi Michael,
> >
> > While verifying virtio frontend drivers of guest OS on qemu with
> > vhost-vdpa backend, we came across feature bits VIRTIO_F_IN_ORDER and
> > VIRTIO_F_NOTIFICATION_DATA, which are introduced in virtio 1.1 spec,
> > are not yet enabled in qemu. These feature flags are very much useful
> > for achieving better virtio-net performance and most of the latest
> hardware VDPA devices supports these feature flags as per of virtio spec.
> 
> Could you share more about which device do you mean? Does Marvell ship
> or intends to ship one?
>
We are planning to ship virtio compliant devices (Marvell CN103/106 DPUs).
 
> > Could you let us know if there are any plans, to add support for these
> > features in upcoming qemu releases.
> > I guess there was some discussion on VIRTIO_F_IN_ORDER feature bit
> > long ago,
> > https://urldefense.proofpoint.com/v2/url?u=https-
> 3A__patchew.org_QEMU_
> > 1533833677-2D27512-2D1-2Dgit-2Dsend-2Demail-2Di.maximets-
> 40samsung.com
> >
> _&d=DwIBAg&c=nKjWec2b6R0mOyPaz7xtfQ&r=Fj4OoD5hcKFpANhTWdwQzj
> T1Jpf7veC5
> > 263T47JVpnc&m=f_dkNKw4UhQulkhjHzd-
> 2YuAvT5n_l_7yuu2r6wSNY2cRHCHnkEM1w2m
> > BEX6Y_yv&s=E3PwNom0AdGnh6dp0WsFPANXX5qH3gAcUYucDyZ6_7Q&e=
> > Seems like that discussion has not reached any conclusion or further work.
> >
> > Thanks,
> > Srujana.
> 
> Yes that patch got comments and these were not addressed.
> Feel free to address them so this can proceed.
> 
We are planning to address the concerns discussed in that mail chain.
> --
> MST

RE: [EXT] Re: Regarding VIRTIO_F_IN_ORDER and VIRTIO_F_NOTIFICATION_DATA feature bits

[Srujana Challa]

> > ----------------------------------------------------------------------
> > On Wed, Dec 13, 2023 at 04:27:40PM +0000, Srujana Challa wrote:
> > > Hi Michael,
> > >
> > > While verifying virtio frontend drivers of guest OS on qemu with
> > > vhost-vdpa backend, we came across feature bits VIRTIO_F_IN_ORDER
> > > and VIRTIO_F_NOTIFICATION_DATA, which are introduced in virtio 1.1
> > > spec, are not yet enabled in qemu. These feature flags are very much
> > > useful for achieving better virtio-net performance and most of the
> > > latest
> > hardware VDPA devices supports these feature flags as per of virtio spec.
> >
> > Could you share more about which device do you mean? Does Marvell ship
> > or intends to ship one?
> >
> We are planning to ship virtio compliant devices (Marvell CN103/106 DPUs).
> 
> > > Could you let us know if there are any plans, to add support for
> > > these features in upcoming qemu releases.
> > > I guess there was some discussion on VIRTIO_F_IN_ORDER feature bit
> > > long ago,
> > > https://urldefense.proofpoint.com/v2/url?u=https-
> > 3A__patchew.org_QEMU_
> > > 1533833677-2D27512-2D1-2Dgit-2Dsend-2Demail-2Di.maximets-
> > 40samsung.com
> > >
> >
> _&d=DwIBAg&c=nKjWec2b6R0mOyPaz7xtfQ&r=Fj4OoD5hcKFpANhTWdwQzj
> > T1Jpf7veC5
> > > 263T47JVpnc&m=f_dkNKw4UhQulkhjHzd-
> > 2YuAvT5n_l_7yuu2r6wSNY2cRHCHnkEM1w2m
> > >
> BEX6Y_yv&s=E3PwNom0AdGnh6dp0WsFPANXX5qH3gAcUYucDyZ6_7Q&e=
> > > Seems like that discussion has not reached any conclusion or further
> work.
> > >
> > > Thanks,
> > > Srujana.
> >
> > Yes that patch got comments and these were not addressed.
> > Feel free to address them so this can proceed.
> >
> We are planning to address the concerns discussed in that mail chain.
Can we make the "vhost-internal" backend with its own set of supported
features? In this case we'll be able to use "host_features" as a set of
features available for negotiation and every backend (including "internal" one)
will negotiate features that it supports, as asked in the above patch thread?

> > --
> > MST