Subject: Re: [RFC PATCH 1/3] powerpc/pseries/iommu: Bring back userspace view for single level TCE tables

From: Michael Ellerman <[email-masked]>
Date: Fri, 22 Mar 2024 16:49:43 +1100

Jason Gunthorpe <[email-masked]> writes:
> On Tue, Mar 12, 2024 at 01:14:20PM -0500, Shivaprasad G Bhat wrote:
>> The commit 090bad39b237a ("powerpc/powernv: Add indirect levels to
>> it_userspace") which implemented the tce indirect levels
>> support for PowerNV ended up removing the single level support
>> which existed by default(generic tce_iommu_userspace_view_alloc/free()
>> calls). On pSeries the TCEs are single level, and the allocation
>> of userspace view is lost with the removal of generic code.
>
> :( :(
>
> If this has been broken since 2018 and nobody cared till now can we
> please go in a direction of moving this code to the new iommu APIs
> instead of doubling down on more of this old stuff that apparently
> almost nobody cares about ??

It's broken *on pseries* (Linux as a guest), but it works fine on
powernv (aka bare metal, aka Linux as Hypervisor).

What's changed is folks are now testing it on pseries with Linux as a
nested hypervisor.

cheers