[PATCH v3 26/28] KVM: selftests: Split out helper to allocate guest mem via memfd

Sean Christopherson
2022-02-26T00:18:08Z

Extract the code for allocating guest memory via memfd out of
vm_userspace_mem_region_add() and into a new helper, kvm_memfd_alloc().
A future selftest to populate a guest with the maximum amount of guest
memory will abuse KVM's memslots to alias guest memory regions to a
single memfd-backed host region, i.e. needs to back a guest with memfd
memory without a 1:1 association between a memslot and a memfd instance.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
.../selftests/kvm/include/kvm_util_base.h | 1 +
tools/testing/selftests/kvm/lib/kvm_util.c | 42 +++++++++++--------
2 files changed, 25 insertions(+), 18 deletions(-)

diff --git a/tools/testing/selftests/kvm/include/kvm_util_base.h b/tools/testing/selftests/kvm/include/kvm_util_base.h
index 573de0354175..92cef0ffb19e 100644
--- a/tools/testing/selftests/kvm/include/kvm_util_base.h
+++ b/tools/testing/selftests/kvm/include/kvm_util_base.h
@@ -123,6 +123,7 @@ int kvm_memcmp_hva_gva(void *hva, struct kvm_vm *vm, const vm_vaddr_t gva,
size_t len);

void kvm_vm_elf_load(struct kvm_vm *vm, const char *filename);
+int kvm_memfd_alloc(size_t size, bool hugepages);

void vm_dump(FILE *stream, struct kvm_vm *vm, uint8_t indent);

diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index dcb8e96c6a54..1665a220abcb 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -718,6 +718,27 @@ void kvm_vm_free(struct kvm_vm *vmp)
free(vmp);
}

+int kvm_memfd_alloc(size_t size, bool hugepages)
+{
+ int memfd_flags = MFD_CLOEXEC;
+ int fd, r;
+
+ if (hugepages)
+ memfd_flags |= MFD_HUGETLB;
+
+ fd = memfd_create("kvm_selftest", memfd_flags);
+ TEST_ASSERT(fd != -1, "memfd_create() failed, errno: %i (%s)",
+ errno, strerror(errno));
+
+ r = ftruncate(fd, size);
+ TEST_ASSERT(!r, "ftruncate() failed, errno: %i (%s)", errno, strerror(errno));
+
+ r = fallocate(fd, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE, 0, size);
+ TEST_ASSERT(!r, "fallocate() failed, errno: %i (%s)", errno, strerror(errno));
+
+ return fd;
+}
+
/*
* Memory Compare, host virtual to guest virtual
*
@@ -970,24 +991,9 @@ void vm_userspace_mem_region_add(struct kvm_vm *vm,
region->mmap_size += alignment;

region->fd = -1;
- if (backing_src_is_shared(src_type)) {
- int memfd_flags = MFD_CLOEXEC;
-
- if (src_type == VM_MEM_SRC_SHARED_HUGETLB)
- memfd_flags |= MFD_HUGETLB;
-
- region->fd = memfd_create("kvm_selftest", memfd_flags);
- 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);
- }
+ if (backing_src_is_shared(src_type))
+ region->fd = kvm_memfd_alloc(region->mmap_size,
+ src_type == VM_MEM_SRC_SHARED_HUGETLB);

region->mmap_start = mmap(NULL, region->mmap_size,
PROT_READ | PROT_WRITE,
--
2.35.1.574.g5d30c73bfb-goog