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

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Message-ID: <20241003133849.GD2456194@ziepe.ca>
Date: Thu, 3 Oct 2024 10:38:49 -0300
From: Jason Gunthorpe <jgg@...pe.ca>
To: Timothy Pearson <tpearson@...torengineering.com>
Cc: Shivaprasad G Bhat <sbhat@...ux.ibm.com>,
	Alex Williamson <alex.williamson@...hat.com>,
	linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
	Michael Ellerman <mpe@...erman.id.au>, npiggin <npiggin@...il.com>,
	christophe leroy <christophe.leroy@...roup.eu>,
	aneesh kumar <aneesh.kumar@...nel.org>,
	naveen n rao <naveen.n.rao@...ux.ibm.com>,
	gbatra <gbatra@...ux.vnet.ibm.com>, brking@...ux.vnet.ibm.com,
	Alexey Kardashevskiy <aik@...abs.ru>, robh@...nel.org,
	linux-kernel <linux-kernel@...r.kernel.org>,
	kvm <kvm@...r.kernel.org>, aik <aik@....com>, msuchanek@...e.de,
	jroedel <jroedel@...e.de>, vaibhav <vaibhav@...ux.ibm.com>,
	svaidy@...ux.ibm.com
Subject: Re: [RFC PATCH 1/3] powerpc/pseries/iommu: Bring back userspace view
 for single level TCE tables

On Tue, Mar 19, 2024 at 01:36:51PM -0500, Timothy Pearson wrote:
> > 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 ??
> 
> Just FYI Raptor is working on porting things over to the new APIs.
> RFC patches should be posted in the next week or two.

There was a discussion about this at LPC a few weeks ago, did any
patches get prepared?

Jason