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KVM: selftests: Split out helper to allocate guest mem via memfd 

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>
Message-Id: <20220226001546.360188-27-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2022-02-26 00:15:44 +00:00 committed by Paolo Bonzini
parent 3d7d6043f3
commit a4187c9bd1
2 changed files with 25 additions and 18 deletions
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1
tools/testing/selftests/kvm/include/kvm_util_base.h
View File

@ -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);

42
tools/testing/selftests/kvm/lib/kvm_util.c
View File

@ -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,