Re: [RFC PATCH 05/16] hw/arm/tegra241-cmdqv: Add initial Tegra241 CMDQ-Virtualisation support

[Nicolin Chen <nicolinc@nvidia.com>]

On Tue, Jan 13, 2026 at 06:41:03AM -0800, Shameer Kolothum wrote:
> > > -    if (!iommufd_backend_alloc_viommu(idev->iommufd, idev->devid,
> > > +    if (s->tegra241_cmdqv && !tegra241_cmdqv_alloc_viommu(s, idev,
> > &viommu_id,
> > > +                                                          errp)) {
> > > +        return false;

> > I am confused. In tegra241_cmdqv_alloc_viommu() it returns false if
> > alloc_viommu fails. but you seem to reset s->tegra241_cmdqv as if you
> > would fall back to non cmdqv setup. What do you try do, fallback or
> > execute either tegra241 code or default code. Or maybe I misunderstand
> > the uapi call sequence?
> 
> No fallback intended. Currently, if the user has enabled tegra241_cmdqv and
> tegra241_cmdqv_alloc_viommu() fails, we fail the device init. Sorry about
> that to reset s->tegra241_cmdqv and !viommu_id logic, , that was a left
> over logic from previous internal branch I had.
> 
> @Nicolin, is there any such requirement for a fallback in this case?

Likely no. I agree that we should do in the cleaner way.

Nicolin