Re: [PATCH v2] vfio: selftests: only build tests on arm64 and x86_64

[David Matlack <dmatlack@google.com>]

On 2026-04-27 06:55 PM, Sean Christopherson wrote:
> On Mon, Apr 27, 2026, Jason Gunthorpe wrote:
> > On Tue, Mar 17, 2026 at 01:55:17PM +0000, Matt Evans wrote:
> > > Hi Ted,
> > > 
> > > On 03/02/2026 01:23, Ted Logan wrote:
> > > > Only build vfio self-tests on arm64 and x86_64; these are the only
> > > > architectures where the vfio self-tests are run. Addresses compiler
> > > > warnings for format and conversions on i386.
> > > > 
> > > > Reported-by: kernel test robot <lkp@intel.com>
> > > > Closes: https://lore.kernel.org/oe-kbuild-all/202601211830.aBEjmEFD-lkp@intel.com/
> > > > Signed-off-by: Ted Logan <tedlogan@fb.com>
> > > > ---
> > > > Do not build vfio self-tests for 32-bit architectures, where they're
> > > > untested and unmaintained. Only build these tests for arm64 and x86_64,
> > > > where they're regularly tested.
> > > > 
> > > > Compiler warning fixed by patch:
> > > > 
> > > >    In file included from tools/testing/selftests/vfio/lib/include/libvfio.h:6:
> > > >    tools/testing/selftests/vfio/lib/include/libvfio/iommu.h:49:2: warning: format specifies type 'unsigned long' but the argument has type 'u64' (aka 'unsigned long long') [-Wformat]
> > > >       49 |         VFIO_ASSERT_EQ(__iommu_unmap(iommu, region, NULL), 0);
> > > >          |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > > >    tools/testing/selftests/vfio/lib/include/libvfio/assert.h:32:37: note: expanded from macro 'VFIO_ASSERT_EQ'
> > > >       32 | #define VFIO_ASSERT_EQ(_a, _b, ...) VFIO_ASSERT_OP(_a, _b, ==, ##__VA_ARGS__)
> > > >          |                                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > > >    tools/testing/selftests/vfio/lib/include/libvfio/assert.h:27:22: note: expanded from macro 'VFIO_ASSERT_OP'
> > > >       26 |         fprintf(stderr, "  Observed: %#lx %s %#lx\n",                           \
> > > >          |                                              ~~~~
> > > >       27 |                         (u64)__lhs, #_op, (u64)__rhs);                          \
> > > >          |                                           ^~~~~~~~~~
> > > > ---
> > > > Changes in v2:
> > > > - Add white space around arch checks
> > > > - Clean up uname command
> > > > - Link to v1: https://lore.kernel.org/r/20260130-vfio-selftest-only-64bit-v1-1-d89ac0944c01@fb.com
> > > > ---
> > > >  tools/testing/selftests/vfio/Makefile | 9 +++++++++
> > > >  1 file changed, 9 insertions(+)
> > > > 
> > > > diff --git a/tools/testing/selftests/vfio/Makefile b/tools/testing/selftests/vfio/Makefile
> > > > index ead27892ab65..8e90e409e91d 100644
> > > > --- a/tools/testing/selftests/vfio/Makefile
> > > > +++ b/tools/testing/selftests/vfio/Makefile
> > > > @@ -1,3 +1,10 @@
> > > > +ARCH ?= $(shell uname -m)
> > > > +
> > > > +ifeq (,$(filter $(ARCH),arm64 x86_64))
> > > 
> > > This fails to build (i.e. elides the build) on my local arm64 machine,
> > > because uname -m returns 'aarch64', not 'arm64'.
> > 
> > I have the same issue on x86! The kernel uses x86 is the ARCH when you
> > run it straight from the top level make
> > 
> > make[4]: Entering directory '/home/jgg/oss/wip/mlx5st/tools/testing/selftests/vfio'
> > Makefile:1: "Saw ARCH=x86"
> > 
> > Even though this is a 64 bit build.
> 
> Heh, it's much funnier when it's happening to someone else.  :-)
> 
> KVM selftests went through these exact pains.  I'm pretty sure these are the
> relevant commits (the empty targets one may or may not apply to VFIO).
> 
> 9af04539d474dda4984ff4909d4568e6123c8cba KVM: selftests: Override ARCH for x86_64 instead of using ARCH_DIR
> 67730e6c53d70fb31618230f81c4acee9f72eaa3 KVM: selftests: Use canonical $(ARCH) paths for KVM selftests directories
> 43fbd8cd389faa9760c5152b1c58e893c812953b KVM: selftests: Provide empty 'all' and 'clean' targets for unsupported ARCHs

KVM selftests don't prevent 32-bit x86 builds though, which is part of what
we're trying to do here.

For example running...

  $ make -C tools/testing/selftests/kvm ARCH=x86 CC="gcc -m32"

...produces a lot of -Wformat errors that were also seeing in VFIO selftests
from the kernel test robot.

I think something like this would fix your issue Jason. I haven't tested it on
ARM yet:

diff --git a/tools/testing/selftests/vfio/Makefile b/tools/testing/selftests/vfio/Makefile
index 0684932d91bf..db71aef6bfb2 100644
--- a/tools/testing/selftests/vfio/Makefile
+++ b/tools/testing/selftests/vfio/Makefile
@@ -1,6 +1,11 @@
 ARCH ?= $(shell uname -m)

-ifeq (,$(filter $(ARCH),aarch64 arm64 x86_64))
+# VFIO selftests are currently only supported on 64-bit x86 and ARM.
+ifneq (,$(filter $(ARCH),x86 x86_64 aarch64 arm64))
+SUPPORTED_ARCH := $(shell echo __LP64__ | $(CC) $(CFLAGS) -E -x c - | tail -n 1)
+endif
+
+ifneq ($(SUPPORTED_ARCH),1)
 # Do nothing on unsupported architectures
 include ../lib.mk
 else