linux-kernel - Re: [PATCH v5 04/27] iommu/io-pgtable-arm: Factor kernel specific code out

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Message-ID: <20251128164541.GA812105@ziepe.ca>
Date: Fri, 28 Nov 2025 12:45:41 -0400
From: Jason Gunthorpe <jgg@...pe.ca>
To: Mostafa Saleh <smostafa@...gle.com>
Cc: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	kvmarm@...ts.linux.dev, iommu@...ts.linux.dev,
	catalin.marinas@....com, will@...nel.org, maz@...nel.org,
	oliver.upton@...ux.dev, joey.gouly@....com, suzuki.poulose@....com,
	yuzenghui@...wei.com, joro@...tes.org, jean-philippe@...aro.org,
	praan@...gle.com, danielmentz@...gle.com, mark.rutland@....com,
	qperret@...gle.com, tabba@...gle.com
Subject: Re: [PATCH v5 04/27] iommu/io-pgtable-arm: Factor kernel specific
 code out

On Mon, Nov 17, 2025 at 06:47:51PM +0000, Mostafa Saleh wrote:
> Some of the used APIs are only part of the kernel and are not
> available in the hypervisor, factor those out:
> - alloc/free memory

Why not provide the iommu-pages API for the hypervisor environment?

Same for virt_to_phys, that could be moved into an iommu-pages wrapper
too..

I want to change other parts of the driver to use iommu-pages in the
long run as well, so putting the abstraction there is probably more
valuable than this.

Also the genericpt stuff is merged, should you (eventually?) be making
a pKVM hypervisor specific set of page table functions? Eg if all you
are doing is mirroring the host stage 2 I think you can build
something much more efficient...

Jason