linux-kernel - Re: [PATCH v2 11/12] iommu/amd: Add support for nested domain attach/detach

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Message-ID: <20251009143558.GC3839422@nvidia.com>
Date: Thu, 9 Oct 2025 11:35:58 -0300
From: Jason Gunthorpe <jgg@...dia.com>
To: Sairaj Kodilkar <sarunkod@....com>
Cc: "Suthikulpanit, Suravee" <suravee.suthikulpanit@....com>,
	nicolinc@...dia.com, linux-kernel@...r.kernel.org,
	robin.murphy@....com, will@...nel.org, joro@...tes.org,
	kevin.tian@...el.com, jsnitsel@...hat.com, vasant.hegde@....com,
	iommu@...ts.linux.dev, santosh.shukla@....com,
	sairaj.arunkodilkar@....com, jon.grimm@....com,
	prashanthpra@...gle.com, wvw@...gle.com, wnliu@...gle.com,
	gptran@...gle.com, kpsingh@...gle.com, joao.m.martins@...cle.com,
	alejandro.j.jimenez@...cle.com
Subject: Re: [PATCH v2 11/12] iommu/amd: Add support for nested domain
 attach/detach

On Thu, Oct 09, 2025 at 12:48:27PM +0530, Sairaj Kodilkar wrote:
> > > Here, we just select only what we needed for configuring guest page table
> > > specifically to be programmed onto the host DTE.
> > Everything you don't pick up should be checked to be 0. VMM needs to
> > filter out unsuopported things or generate a bad DTE error.
> An alternative can be to introduce a struct which only contains relevant
> fields.

We don't want this as a uAPI, use the normal DTE and have the kernel
check the things it currently support. Future kernels can support new
things through the same ABI.

VMM is reponsible to 0 out things the kernel shouldn't see or it
handles on its own.

Jason