KVM: selftests: add shmem backing source type

This lets us run the demand paging test on top of a shmem-backed area.
In follow-up commits, we'll 1) leverage this new capability to create an
alias mapping, and then 2) use the alias mapping to exercise UFFD minor
faults.

Signed-off-by: Axel Rasmussen <axelrasmussen@google.com>
Message-Id: <20210519200339.829146-8-axelrasmussen@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/tools/testing/selftests/kvm/include/test_util.h b/tools/testing/selftests/kvm/include/test_util.h
index fade313..7377f00 100644 (file)
--- a/tools/testing/selftests/kvm/include/test_util.h
+++ b/tools/testing/selftests/kvm/include/test_util.h
@@ -84,6 +84,7 @@ enum vm_mem_backing_src_type {
        VM_MEM_SRC_ANONYMOUS_HUGETLB_1GB,
        VM_MEM_SRC_ANONYMOUS_HUGETLB_2GB,
        VM_MEM_SRC_ANONYMOUS_HUGETLB_16GB,
+       VM_MEM_SRC_SHMEM,
        NUM_SRC_TYPES,
 };
 

diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index 491be22..bc50ca6 100644 (file)
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -847,10 +847,25 @@ void vm_userspace_mem_region_add(struct kvm_vm *vm,
        if (alignment > 1)
                region->mmap_size += alignment;
 
+       region->fd = -1;
+       if (src_type == VM_MEM_SRC_SHMEM) {
+               region->fd = memfd_create("kvm_selftest", MFD_CLOEXEC);
+               TEST_ASSERT(region->fd != -1,
+                           "memfd_create failed, errno: %i", errno);
+
+               ret = ftruncate(region->fd, region->mmap_size);
+               TEST_ASSERT(ret == 0, "ftruncate failed, errno: %i", errno);
+
+               ret = fallocate(region->fd,
+                               FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE, 0,
+                               region->mmap_size);
+               TEST_ASSERT(ret == 0, "fallocate failed, errno: %i", errno);
+       }
+
        region->mmap_start = mmap(NULL, region->mmap_size,
                                  PROT_READ | PROT_WRITE,
                                  vm_mem_backing_src_alias(src_type)->flag,
-                                 -1, 0);
+                                 region->fd, 0);
        TEST_ASSERT(region->mmap_start != MAP_FAILED,
                    "test_malloc failed, mmap_start: %p errno: %i",
                    region->mmap_start, errno);

diff --git a/tools/testing/selftests/kvm/lib/test_util.c b/tools/testing/selftests/kvm/lib/test_util.c
index 06ddde0..c7a265d 100644 (file)
--- a/tools/testing/selftests/kvm/lib/test_util.c
+++ b/tools/testing/selftests/kvm/lib/test_util.c
@@ -236,6 +236,10 @@ const struct vm_mem_backing_src_alias *vm_mem_backing_src_alias(uint32_t i)
                        .name = "anonymous_hugetlb_16gb",
                        .flag = anon_huge_flags | MAP_HUGE_16GB,
                },
+               [VM_MEM_SRC_SHMEM] = {
+                       .name = "shmem",
+                       .flag = MAP_SHARED,
+               },
        };
        _Static_assert(ARRAY_SIZE(aliases) == NUM_SRC_TYPES,
                       "Missing new backing src types?");
@@ -253,6 +257,7 @@ size_t get_backing_src_pagesz(uint32_t i)
 
        switch (i) {
        case VM_MEM_SRC_ANONYMOUS:
+       case VM_MEM_SRC_SHMEM:
                return getpagesize();
        case VM_MEM_SRC_ANONYMOUS_THP:
                return get_trans_hugepagesz();