> -----Original Message-----
> From: Nicolin Chen <[email protected]>
> Sent: 30 December 2025 17:54
> To: Shameer Kolothum <[email protected]>
> Cc: [email protected]; [email protected];
> [email protected]; [email protected]; Nathan Chen
> <[email protected]>; Matt Ochs <[email protected]>; Jason Gunthorpe
> <[email protected]>; [email protected];
> [email protected]; [email protected]; Krishnakant Jaju
> <[email protected]>
> Subject: Re: [RFC PATCH 10/16] hw/arm/tegra241-cmdqv: Allocate vEVENTQ
> object
>
> On Tue, Dec 30, 2025 at 01:47:08AM -0800, Shameer Kolothum wrote:
> > > From: Nicolin Chen <[email protected]>
> > > Sent: 29 December 2025 19:50
> > > To: Shameer Kolothum <[email protected]>
> > > Cc: [email protected]; [email protected];
> > > [email protected]; [email protected]; Nathan Chen
> > > <[email protected]>; Matt Ochs <[email protected]>; Jason
> Gunthorpe
> > > <[email protected]>; [email protected];
> > > [email protected]; [email protected]; Krishnakant Jaju
> > > <[email protected]>
> > > Subject: Re: [RFC PATCH 10/16] hw/arm/tegra241-cmdqv: Allocate
> vEVENTQ
> > > object
> > >
> > > On Wed, Dec 10, 2025 at 01:37:31PM +0000, Shameer Kolothum wrote:
> > > > @@ -259,11 +305,16 @@ static bool
> > > tegra241_cmdqv_setup_vcmdq(Tegra241CMDQV *cmdqv, int index,
> > > > g_free(vcmdq);
> > > > }
> > > >
> > > > + if (!tegra241_cmdqv_alloc_veventq(cmdqv, errp)) {
> > > > + return false;
> > > > + }
> > > > +
> > >
> > > I think this should be called in tegra241_cmdqv_alloc_viommu().
> >
> > Should/Can we? _alloc_viommu() will happen before the Guest boot.
>
> I think we can. vEVENTQ only needs vIOMMU ID. It's per VINTF v.s.
> per VCMDQ (HW_QUEUE). So, it should follow vIOMMU.
>
> Basically, we can allocate vIOMMU (VINTF) and its vEVENTQ even if
> the VINTF doesn't contain any LVCMDQs, which are allocated/mapped
> to the VINTF later via HW_QUEUE allocations.
But what happens when you receive an event from host during that time?
Should we just ignore it? Or is that not possible at all from a hoist driver
perspective? To me, it looks like the natural flow is setup vEVENTQ when
Guest is ready to receive the events.
> > Unlike the SMMUv3 vEVENTQ for accel case, we restrict the hotplug
> > use case when the tegra214-cmdqv is set. And as soon as Guest setup
> vCMDQ
> > the vEVENTQ is enabled here. Do you see any issues with this approach?
>
> Once guest OS is booting, !tegra241_cmdqv_alloc_veventq will fail
> tegra241_cmdqv_setup_vcmdq while it cannot break the guest OS any
> more. Then, the whole thing wouldn't work although guest OS runs?
If vEVENTQ is mandatory we could exit the Guest with a proper msg in
case tegra241_cmdqv_alloc_veventq() fails, right?
Thanks,
Shameer
>
