Not all IOMMUs support the same virtual address width as the processor,
for instance older Intel consumer platforms only support 39-bits of
IOMMU address space.  On such platforms, using the virtual address as
the IOVA and mappings at the top of the address space both fail.

VFIO and IOMMUFD have facilities for retrieving valid IOVA ranges,
VFIO_IOMMU_TYPE1_INFO_CAP_IOVA_RANGE and IOMMU_IOAS_IOVA_RANGES,
respectively.  These provide compatible arrays of ranges from which
we can construct a simple allocator and record the maximum supported
IOVA address.

Use this new allocator in place of reusing the virtual address, and
incorporate the maximum supported IOVA into the limit testing.  This
latter change doesn't test quite the same absolute end-of-address space
behavior but still seems to have some value.  Testing for overflow is
skipped when a reduced address space is supported as the desired errno
is not generated.

This series is based on Alex Williamson's "Incorporate IOVA range info"
[1] along with feedback from the discussion in David Matlack's "Skip
vfio_dma_map_limit_test if mapping returns -EINVAL" [2].

Given David's plans to split IOMMU concerns from devices as described in
[3], this series' home for `struct iova_allocator` and IOVA
range helpers are likely to be short lived, since they reside in
vfio_pci_device.c. I assume that the rework can move this functionality
to a more appropriate location next to other IOMMU-focused code, once
such a place exists.

[1] https://lore.kernel.org/all/20251108212954.26477-1-alex@shazbot.org/#t
[2] https://lore.kernel.org/all/20251107222058.2009244-1-dmatlack@google.com/
[3] https://lore.kernel.org/all/aRIoKJk0uwLD-yGr@google.com/

To: Alex Williamson <alex@shazbot.org>
To: David Matlack <dmatlack@google.com>
To: Shuah Khan <shuah@kernel.org>
To: Jason Gunthorpe <jgg@ziepe.ca>
Cc: kvm@vger.kernel.org
Cc: linux-kselftest@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Alex Mastro <amastro@fb.com>

Changes in v2:
- Fix various nits
- calloc() where appropriate
- Update overflow test to run regardless of iova range constraints
- Change iova_allocator_init() to return an allocated struct
- Unfold iova_allocator_alloc()
- Fix iova allocator initial state bug
- Update vfio_pci_driver_test to use iova allocator
- Link to v1: https://lore.kernel.org/r/20251110-iova-ranges-v1-0-4d441cf5bf6d@fb.com

---
Alex Mastro (4):
      vfio: selftests: add iova range query helpers
      vfio: selftests: fix map limit tests to use last available iova
      vfio: selftests: add iova allocator
      vfio: selftests: replace iova=vaddr with allocated iovas

 .../testing/selftests/vfio/lib/include/vfio_util.h |  19 +-
 tools/testing/selftests/vfio/lib/vfio_pci_device.c | 241 ++++++++++++++++++++-
 .../testing/selftests/vfio/vfio_dma_mapping_test.c |  20 +-
 .../testing/selftests/vfio/vfio_pci_driver_test.c  |  12 +-
 4 files changed, 283 insertions(+), 9 deletions(-)
---
base-commit: 0ed3a30fd996cb0cac872432cf25185fda7e5316
change-id: 20251110-iova-ranges-1c09549fbf63

Best regards,
-- 
Alex Mastro <amastro@fb.com>

On 2025-11-11 06:52 AM, Alex Mastro wrote:
> Not all IOMMUs support the same virtual address width as the processor,
> for instance older Intel consumer platforms only support 39-bits of
> IOMMU address space.  On such platforms, using the virtual address as
> the IOVA and mappings at the top of the address space both fail.
> 
> VFIO and IOMMUFD have facilities for retrieving valid IOVA ranges,
> VFIO_IOMMU_TYPE1_INFO_CAP_IOVA_RANGE and IOMMU_IOAS_IOVA_RANGES,
> respectively.  These provide compatible arrays of ranges from which
> we can construct a simple allocator and record the maximum supported
> IOVA address.
> 
> Use this new allocator in place of reusing the virtual address, and
> incorporate the maximum supported IOVA into the limit testing.  This
> latter change doesn't test quite the same absolute end-of-address space
> behavior but still seems to have some value.  Testing for overflow is
> skipped when a reduced address space is supported as the desired errno
> is not generated.
> 
> This series is based on Alex Williamson's "Incorporate IOVA range info"
> [1] along with feedback from the discussion in David Matlack's "Skip
> vfio_dma_map_limit_test if mapping returns -EINVAL" [2].
> 
> Given David's plans to split IOMMU concerns from devices as described in
> [3], this series' home for `struct iova_allocator` and IOVA
> range helpers are likely to be short lived, since they reside in
> vfio_pci_device.c. I assume that the rework can move this functionality
> to a more appropriate location next to other IOMMU-focused code, once
> such a place exists.
> 
> [1] https://lore.kernel.org/all/20251108212954.26477-1-alex@shazbot.org/#t
> [2] https://lore.kernel.org/all/20251107222058.2009244-1-dmatlack@google.com/
> [3] https://lore.kernel.org/all/aRIoKJk0uwLD-yGr@google.com/
> 
> To: Alex Williamson <alex@shazbot.org>
> To: David Matlack <dmatlack@google.com>
> To: Shuah Khan <shuah@kernel.org>
> To: Jason Gunthorpe <jgg@ziepe.ca>
> Cc: kvm@vger.kernel.org
> Cc: linux-kselftest@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> Signed-off-by: Alex Mastro <amastro@fb.com>

LGTM. And I confirmed this fixes vfio_dma_mapping_test on HW that does
not support IOVA 0xffffffffffffffff. Thanks!

Reviewed-by: David Matlack <dmatlack@google.com>
Tested-by: David Matlack <dmatlack@google.com>

On Tue, Nov 11, 2025 at 05:41:04PM +0000, David Matlack wrote:
> On 2025-11-11 06:52 AM, Alex Mastro wrote:
> > Not all IOMMUs support the same virtual address width as the processor,
> > for instance older Intel consumer platforms only support 39-bits of
> > IOMMU address space.  On such platforms, using the virtual address as
> > the IOVA and mappings at the top of the address space both fail.
> > 
> > VFIO and IOMMUFD have facilities for retrieving valid IOVA ranges,
> > VFIO_IOMMU_TYPE1_INFO_CAP_IOVA_RANGE and IOMMU_IOAS_IOVA_RANGES,
> > respectively.  These provide compatible arrays of ranges from which
> > we can construct a simple allocator and record the maximum supported
> > IOVA address.
> > 
> > Use this new allocator in place of reusing the virtual address, and
> > incorporate the maximum supported IOVA into the limit testing.  This
> > latter change doesn't test quite the same absolute end-of-address space
> > behavior but still seems to have some value.  Testing for overflow is
> > skipped when a reduced address space is supported as the desired errno
> > is not generated.
> > 
> > This series is based on Alex Williamson's "Incorporate IOVA range info"
> > [1] along with feedback from the discussion in David Matlack's "Skip
> > vfio_dma_map_limit_test if mapping returns -EINVAL" [2].
> > 
> > Given David's plans to split IOMMU concerns from devices as described in
> > [3], this series' home for `struct iova_allocator` and IOVA
> > range helpers are likely to be short lived, since they reside in
> > vfio_pci_device.c. I assume that the rework can move this functionality
> > to a more appropriate location next to other IOMMU-focused code, once
> > such a place exists.
> > 
> > [1] https://lore.kernel.org/all/20251108212954.26477-1-alex@shazbot.org/#t
> > [2] https://lore.kernel.org/all/20251107222058.2009244-1-dmatlack@google.com/
> > [3] https://lore.kernel.org/all/aRIoKJk0uwLD-yGr@google.com/
> > 
> > To: Alex Williamson <alex@shazbot.org>
> > To: David Matlack <dmatlack@google.com>
> > To: Shuah Khan <shuah@kernel.org>
> > To: Jason Gunthorpe <jgg@ziepe.ca>
> > Cc: kvm@vger.kernel.org
> > Cc: linux-kselftest@vger.kernel.org
> > Cc: linux-kernel@vger.kernel.org
> > Signed-off-by: Alex Mastro <amastro@fb.com>
> 
> LGTM. And I confirmed this fixes vfio_dma_mapping_test on HW that does
> not support IOVA 0xffffffffffffffff. Thanks!
> 
> Reviewed-by: David Matlack <dmatlack@google.com>
> Tested-by: David Matlack <dmatlack@google.com>

Thanks David!

On Tue, 11 Nov 2025 06:52:01 -0800
Alex Mastro <amastro@fb.com> wrote:

> Not all IOMMUs support the same virtual address width as the processor,
> for instance older Intel consumer platforms only support 39-bits of
> IOMMU address space.  On such platforms, using the virtual address as
> the IOVA and mappings at the top of the address space both fail.
> 
> VFIO and IOMMUFD have facilities for retrieving valid IOVA ranges,
> VFIO_IOMMU_TYPE1_INFO_CAP_IOVA_RANGE and IOMMU_IOAS_IOVA_RANGES,
> respectively.  These provide compatible arrays of ranges from which
> we can construct a simple allocator and record the maximum supported
> IOVA address.
> 
> Use this new allocator in place of reusing the virtual address, and
> incorporate the maximum supported IOVA into the limit testing.  This
> latter change doesn't test quite the same absolute end-of-address space
> behavior but still seems to have some value.  Testing for overflow is
> skipped when a reduced address space is supported as the desired errno
> is not generated.
> 
> This series is based on Alex Williamson's "Incorporate IOVA range info"
> [1] along with feedback from the discussion in David Matlack's "Skip
> vfio_dma_map_limit_test if mapping returns -EINVAL" [2].
> 
> Given David's plans to split IOMMU concerns from devices as described in
> [3], this series' home for `struct iova_allocator` and IOVA
> range helpers are likely to be short lived, since they reside in
> vfio_pci_device.c. I assume that the rework can move this functionality
> to a more appropriate location next to other IOMMU-focused code, once
> such a place exists.
> 
> [1] https://lore.kernel.org/all/20251108212954.26477-1-alex@shazbot.org/#t
> [2] https://lore.kernel.org/all/20251107222058.2009244-1-dmatlack@google.com/
> [3] https://lore.kernel.org/all/aRIoKJk0uwLD-yGr@google.com/
> 
> To: Alex Williamson <alex@shazbot.org>
> To: David Matlack <dmatlack@google.com>
> To: Shuah Khan <shuah@kernel.org>
> To: Jason Gunthorpe <jgg@ziepe.ca>
> Cc: kvm@vger.kernel.org
> Cc: linux-kselftest@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> Signed-off-by: Alex Mastro <amastro@fb.com>
> 
> Changes in v2:
> - Fix various nits
> - calloc() where appropriate
> - Update overflow test to run regardless of iova range constraints
> - Change iova_allocator_init() to return an allocated struct
> - Unfold iova_allocator_alloc()
> - Fix iova allocator initial state bug
> - Update vfio_pci_driver_test to use iova allocator
> - Link to v1: https://lore.kernel.org/r/20251110-iova-ranges-v1-0-4d441cf5bf6d@fb.com

Minor comments, but otherwise LGTM and passes testing on a Kaby Lake
system with limited IOMMU address width.  Thanks,

Alex