On Fri Apr 10, 2026 at 3:20 PM UTC, Nikita Kalyazin wrote: > From: Patrick Roy <[email protected]> > > Allow selftests to configure their memslots such that userspace_addr is > set to a MAP_SHARED mapping of the guest_memfd that's associated with > the memslot. This setup is the configuration for non-CoCo VMs, where all > guest memory is backed by a guest_memfd whose folios are all marked > shared, but KVM is still able to access guest memory to provide > functionality such as MMIO emulation on x86. > > Add backing types for normal guest_memfd, as well as direct map removed > guest_memfd. > > Signed-off-by: Patrick Roy <[email protected]> > Signed-off-by: Nikita Kalyazin <[email protected]> > --- > .../testing/selftests/kvm/include/kvm_util.h | 18 ++++++ > .../testing/selftests/kvm/include/test_util.h | 7 +++ > tools/testing/selftests/kvm/lib/kvm_util.c | 61 ++++++++++--------- > tools/testing/selftests/kvm/lib/test_util.c | 8 +++ > 4 files changed, 65 insertions(+), 29 deletions(-) > > diff --git a/tools/testing/selftests/kvm/include/kvm_util.h > b/tools/testing/selftests/kvm/include/kvm_util.h > index 8b39cb919f4f..056a003a63c0 100644 > --- a/tools/testing/selftests/kvm/include/kvm_util.h > +++ b/tools/testing/selftests/kvm/include/kvm_util.h > @@ -664,6 +664,24 @@ static inline bool is_smt_on(void) > > void vm_create_irqchip(struct kvm_vm *vm); > > +static inline uint32_t backing_src_guest_memfd_flags(enum > vm_mem_backing_src_type t) > +{ > + uint32_t flags = 0; > + > + switch (t) { > + case VM_MEM_SRC_GUEST_MEMFD_NO_DIRECT_MAP: > + flags |= GUEST_MEMFD_FLAG_NO_DIRECT_MAP; > + fallthrough; > + case VM_MEM_SRC_GUEST_MEMFD: > + flags |= GUEST_MEMFD_FLAG_MMAP | GUEST_MEMFD_FLAG_INIT_SHARED; > + break; > + default: > + break; > + } > + > + return flags; > +} > + > static inline int __vm_create_guest_memfd(struct kvm_vm *vm, uint64_t size, > uint64_t flags) > { > diff --git a/tools/testing/selftests/kvm/include/test_util.h > b/tools/testing/selftests/kvm/include/test_util.h > index 8140e59b59e5..ea6de20ce8ef 100644 > --- a/tools/testing/selftests/kvm/include/test_util.h > +++ b/tools/testing/selftests/kvm/include/test_util.h > @@ -152,6 +152,8 @@ enum vm_mem_backing_src_type { > VM_MEM_SRC_ANONYMOUS_HUGETLB_16GB, > VM_MEM_SRC_SHMEM, > VM_MEM_SRC_SHARED_HUGETLB, > + VM_MEM_SRC_GUEST_MEMFD, > + VM_MEM_SRC_GUEST_MEMFD_NO_DIRECT_MAP, > NUM_SRC_TYPES, > }; > > @@ -184,6 +186,11 @@ static inline bool backing_src_is_shared(enum > vm_mem_backing_src_type t) > return vm_mem_backing_src_alias(t)->flag & MAP_SHARED; > } > > +static inline bool backing_src_is_guest_memfd(enum vm_mem_backing_src_type t) > +{ > + return t == VM_MEM_SRC_GUEST_MEMFD || t == > VM_MEM_SRC_GUEST_MEMFD_NO_DIRECT_MAP; > +} > + > static inline bool backing_src_can_be_huge(enum vm_mem_backing_src_type t) > { > return t != VM_MEM_SRC_ANONYMOUS && t != VM_MEM_SRC_SHMEM; > diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c > b/tools/testing/selftests/kvm/lib/kvm_util.c > index 5b0865683047..fa4a2fc236fe 100644 > --- a/tools/testing/selftests/kvm/lib/kvm_util.c > +++ b/tools/testing/selftests/kvm/lib/kvm_util.c > @@ -1046,6 +1046,33 @@ void vm_mem_add(struct kvm_vm *vm, enum > vm_mem_backing_src_type src_type, > alignment = 1; > #endif > > + if (guest_memfd < 0) { > + if ((flags & KVM_MEM_GUEST_MEMFD) || > backing_src_is_guest_memfd(src_type)) { > + uint32_t guest_memfd_flags = > backing_src_guest_memfd_flags(src_type); > + > + TEST_ASSERT(!guest_memfd_offset, > + "Offset must be zero when creating new > guest_memfd"); > + guest_memfd = vm_create_guest_memfd(vm, mem_size, > guest_memfd_flags); > + } > + } else { > + /* > + * Install a unique fd for each memslot so that the fd > + * can be closed when the region is deleted without > + * needing to track if the fd is owned by the framework > + * or by the caller. > + */ > + guest_memfd = kvm_dup(guest_memfd); > + } > + > + if (guest_memfd >= 0) { > + flags |= KVM_MEM_GUEST_MEMFD; > + > + region->region.guest_memfd = guest_memfd; > + region->region.guest_memfd_offset = guest_memfd_offset; > + } else { > + region->region.guest_memfd = -1; > + } > + > /* > * When using THP mmap is not guaranteed to returned a hugepage aligned > * address so we have to pad the mmap. Padding is not needed for HugeTLB > @@ -1061,10 +1088,13 @@ void vm_mem_add(struct kvm_vm *vm, enum > vm_mem_backing_src_type src_type, > if (alignment > 1) > region->mmap_size += alignment; > > - region->fd = -1; > - if (backing_src_is_shared(src_type)) > + if (backing_src_is_guest_memfd(src_type)) > + region->fd = guest_memfd;
This seems to cause a double-close in __vm_mem_region_delete() - it was fine when this patch was written but now we have kvm_free_fd() which crashes the test when this happens. AFAICS it's easy to fix we just need to enlighten __vm_mem_region_delete() that they might be the same FD.
