Re: [RFC PATCH 4/6] selftests/vfio: Exercise sPAPR DDW path for hugepage DMA mappings

[David Matlack <dmatlack@google.com>]

On 2026-07-02 11:28 PM, Narayana Murty N wrote:
> Prepare the DMA window before IOVA allocation in the DMA mapping tests.
> 
> Anonymous mappings use the default sPAPR DMA window. HugeTLB mappings force
> a DDW with the requested page size, allowing the test to exercise DDW
> creation, mapping, unmapping, and cleanup.
> 
> Skip gracefully when hugepage allocation fails or when the platform does
> not support the requested DDW characteristics. Also skip unmap-all when
> the backend cannot pair it with the sPAPR memory unregister flow.
> 
> Signed-off-by: Narayana Murty N <nnmlinux@linux.ibm.com>
> ---
>  .../selftests/vfio/vfio_dma_mapping_test.c    | 22 +++++++++++++++++++
>  1 file changed, 22 insertions(+)
> 
> diff --git a/tools/testing/selftests/vfio/vfio_dma_mapping_test.c b/tools/testing/selftests/vfio/vfio_dma_mapping_test.c
> index 7d0de8c79de1..4411fdbd56da 100644
> --- a/tools/testing/selftests/vfio/vfio_dma_mapping_test.c
> +++ b/tools/testing/selftests/vfio/vfio_dma_mapping_test.c
> @@ -1,5 +1,6 @@
>  // SPDX-License-Identifier: GPL-2.0-only
>  #include <stdio.h>
> +#include <string.h>
>  #include <sys/mman.h>
>  #include <unistd.h>
>  
> @@ -119,8 +120,19 @@ FIXTURE_VARIANT_ADD_ALL_IOMMU_MODES(anonymous_hugetlb_1gb, SZ_1G, MAP_HUGETLB |
>  
>  FIXTURE_SETUP(vfio_dma_mapping_test)
>  {
> +	const u64 page_size = variant->size ?: getpagesize();
> +	const bool force_dynamic = !!variant->size;

This is kind of arbitrary right? Should we add explicit variants for
dynamic/default windows (see below). But we need some way to skip the dynamic
window tests on non-spapr iommus...

diff --git a/tools/testing/selftests/vfio/vfio_dma_mapping_test.c b/tools/testing/selftests/vfio/vfio_dma_mapping_test.c
index cd2d3276a46c..b54c529ebedb 100644
--- a/tools/testing/selftests/vfio/vfio_dma_mapping_test.c
+++ b/tools/testing/selftests/vfio/vfio_dma_mapping_test.c
@@ -103,15 +103,21 @@ FIXTURE_VARIANT(vfio_dma_mapping_test) {
        const char *iommu_mode;
        u64 size;
        int mmap_flags;
+       bool dynamic_window;
 };

-#define FIXTURE_VARIANT_ADD_IOMMU_MODE(_iommu_mode, _name, _size, _mmap_flags) \
-FIXTURE_VARIANT_ADD(vfio_dma_mapping_test, _iommu_mode ## _ ## _name) {               \
-       .iommu_mode = #_iommu_mode,                                            \
-       .size = (_size),                                                       \
-       .mmap_flags = MAP_ANONYMOUS | MAP_PRIVATE | (_mmap_flags),             \
+#define __FIXTURE_VARIANT_ADD_IOMMU_MODE(_iommu_mode, _name, _size, _mmap_flags, _dynamic_window) \
+FIXTURE_VARIANT_ADD(vfio_dma_mapping_test,_iommu_mode ## _ ## _name) {   \
+       .iommu_mode = #_iommu_mode,                                                               \
+       .size = (_size),                                                                          \
+       .mmap_flags = MAP_ANONYMOUS | MAP_PRIVATE | (_mmap_flags),                                \
+       .dynamic_window = _dynamic_window,                                                        \
 }

+#define FIXTURE_VARIANT_ADD_IOMMU_MODE(_iommu_mode, _name, _size, _mmap_flags)  \
+__FIXTURE_VARIANT_ADD_IOMMU_MODE(_iommu_mode, _name, _size, _mmap_flags, false); \
+__FIXTURE_VARIANT_ADD_IOMMU_MODE(_iommu_mode, _name ## _dynamic_window, _size, _mmap_flags, true) \
+
 FIXTURE_VARIANT_ADD_ALL_IOMMU_MODES(anonymous, 0, 0);
 FIXTURE_VARIANT_ADD_ALL_IOMMU_MODES(anonymous_hugetlb_2mb, SZ_2M, MAP_HUGETLB | MAP_HUGE_2MB);
 FIXTURE_VARIANT_ADD_ALL_IOMMU_MODES(anonymous_hugetlb_1gb, SZ_1G, MAP_HUGETLB | MAP_HUGE_1GB);
@@ -121,14 +127,13 @@ FIXTURE_VARIANT_ADD_ALL_IOMMU_MODES(anonymous_hugetlb_1gb, SZ_1G, MAP_HUGETLB |
 FIXTURE_SETUP(vfio_dma_mapping_test)
 {
        const u64 page_size = variant->size ?: getpagesize();
-       const bool force_dynamic = !!variant->size;
        int ret;

        self->iommu = iommu_init(variant->iommu_mode);
        self->device = vfio_pci_device_init(device_bdf, self->iommu);

        ret = iommu_prepare_dma_window(self->iommu, page_size, page_size,
-                                      force_dynamic);
+                                      variant->dynamic_window);
        if (ret)
                SKIP(return, "DMA window unavailable: %s (%d)\n",
                     strerror(-ret), -ret);

> +	int ret;
> +
>  	self->iommu = iommu_init(variant->iommu_mode);
>  	self->device = vfio_pci_device_init(device_bdf, self->iommu);
> +
> +	ret = iommu_prepare_dma_window(self->iommu, page_size, page_size,
> +				       force_dynamic);
> +	if (ret)
> +		SKIP(return, "DMA window unavailable: %s (%d)\n",
> +		     strerror(-ret), -ret);
> +
>  	self->iova_allocator = iova_allocator_init(self->iommu);
>  }
>  
> @@ -227,6 +239,7 @@ FIXTURE_SETUP(vfio_dma_map_limit_test)
>  	u64 region_size = getpagesize();
>  	iova_t last_iova;
>  	u32 nranges;
> +	int ret;
>  
>  	/*
>  	 * Over-allocate mmap by double the size to provide enough backing vaddr
> @@ -236,6 +249,13 @@ FIXTURE_SETUP(vfio_dma_map_limit_test)
>  
>  	self->iommu = iommu_init(variant->iommu_mode);
>  	self->device = vfio_pci_device_init(device_bdf, self->iommu);
> +
> +	ret = iommu_prepare_dma_window(self->iommu, region_size, region_size,
> +				       false);
> +	if (ret)
> +		SKIP(return, "DMA window unavailable: %s (%d)\n",
> +		     strerror(-ret), -ret);
> +
>  	region->vaddr = mmap(NULL, self->mmap_size, PROT_READ | PROT_WRITE,
>  			     MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
>  	ASSERT_NE(region->vaddr, MAP_FAILED);
> @@ -277,6 +297,8 @@ TEST_F(vfio_dma_map_limit_test, unmap_all)
>  	u64 unmapped;
>  	int rc;
>  
> +	if (!iommu_supports_unmap_all(self->iommu))
> +		SKIP(return, "IOMMU backend does not support unmap-all\n");
>  	iommu_map(self->iommu, region);
>  	ASSERT_EQ(region->iova, to_iova(self->device, region->vaddr));
>  
> -- 
> 2.51.1
>