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

[Narayana Murty N <nnmlinux@linux.ibm.com>]

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;
+	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