linux-kernel - Re: [PATCH] genpt: Make GENERIC

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Message-ID: <CAMuHMdVsyu_vnYiV7EcChd3a6czUCh4Gis3hL8uDVmbDcGo06w@mail.gmail.com>
Date: Thu, 20 Nov 2025 19:31:10 +0100
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Jason Gunthorpe <jgg@...pe.ca>
Cc: Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>, 
	Robin Murphy <robin.murphy@....com>, iommu@...ts.linux.dev, linux-kernel@...r.kernel.org, 
	KUnit Development <kunit-dev@...glegroups.com>, 
	"open list:KERNEL SELFTEST FRAMEWORK" <linux-kselftest@...r.kernel.org>
Subject: Re: [PATCH] genpt: Make GENERIC_PT invisible

Hi Jason,

CC kunit

On Thu, 20 Nov 2025 at 18:07, Jason Gunthorpe <jgg@...pe.ca> wrote:
> On Thu, Nov 20, 2025 at 12:49:33PM -0400, Jason Gunthorpe wrote:
> > On Wed, Nov 12, 2025 at 03:08:05PM +0100, Geert Uytterhoeven wrote:
> > > There is no point in asking the user about the Generic Radix Page
> > > Table API:
> > >   - All IOMMU drivers that use this API already select GENERIC_PT when
> > >     needed,
> > >   - Most users probably do not know what to answer anyway.
> > >
> > > Fixes: 7c5b184db7145fd4 ("genpt: Generic Page Table base API")
> > > Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
> > > ---
> > >  drivers/iommu/generic_pt/Kconfig | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > Reviewed-by: Jason Gunthorpe <jgg@...dia.com>
>
> Actually, it doesn't work :\
>
> $ tools/testing/kunit/kunit.py run --build_dir build_kunit_x86_64 --arch x86_64 --kunitconfig ./drivers/iommu/generic_pt/.kunitconfig
> [13:01:26] Configuring KUnit Kernel ...
> [13:01:26] Building KUnit Kernel ...
> Populating config with:
> $ make ARCH=x86_64 O=build_kunit_x86_64 olddefconfig
> Building with:
> $ make all compile_commands.json scripts_gdb ARCH=x86_64 O=build_kunit_x86_64 --jobs=20
> ERROR:root:Not all Kconfig options selected in kunitconfig were in the generated .config.
> This is probably due to unsatisfied dependencies.
> Missing: CONFIG_IOMMUFD_TEST=y, CONFIG_DEBUG_GENERIC_PT=y, CONFIG_IOMMU_PT_VTDSS=y, CONFIG_IOMMU_PT=y, CONFIG_IOMMU_PT_AMDV1=y, CONFIG_IOMMU_PT_X86_64=y, CONFIG_GENERIC_PT=y, CONFIG_IOMMU_PT_KUNIT_TEST=y
>
> Can you add this hunk and send a v2?
>
> --- a/drivers/iommu/generic_pt/.kunitconfig
> +++ b/drivers/iommu/generic_pt/.kunitconfig
> @@ -1,4 +1,5 @@
>  CONFIG_KUNIT=y
> +CONFIG_COMPILE_TEST=y
>  CONFIG_GENERIC_PT=y
>  CONFIG_DEBUG_GENERIC_PT=y
>  CONFIG_IOMMU_PT=y

Do you really want to enable CONFIG_COMPILE_TEST in a .kunitconfig?

Hm, that .kunitconfig already enables IOMMUFD_TEST, which is
documented to be dangerous (why?), and already enabled by allyesconfig
(except on GENERIC_ATOMIC64 architectures).
IOMMUFD_TEST cannot select GENERIC_PT, as that would lead to
a recursive dependency (and I am not a huge fan of test code auto-enabling
extra attack surfaces^W^W functionality).

Or perhaps:

-       bool "Generic Radix Page Table"
+       bool "Generic Radix Page Table" if COMPILE_TEST || KUNIT

?

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds