On 8/25/2026 5:32 PM, Ackerley Tng wrote:
Sean Christopherson <[email protected]> writes:
On Fri, Aug 21, 2026, Xiaoyao Li wrote:
On 8/8/2026 5:53 AM, Ackerley Tng via B4 Relay wrote:
From: Ackerley Tng<[email protected]>
Update the private memory conversions selftest to also test conversions
that are done "in-place" via per-guest_memfd memory attributes. In-place
conversions require the host to be able to mmap() the guest_memfd so that
the host and guest can share the same backing physical memory.
This includes several updates, that are conditioned on the system
supporting per-guest_memfd attributes (kvm_has_gmem_attributes):
1. Set up guest_memfd requesting MMAP and INIT_SHARED.
If I understand correctly, even with in-place gmem, the model that shared
memory comes from the userspace_addr and private memory comes from gmem can
still work without passing GUEST_MEMFD_FLAG_MMAP flag.
Since this model is not prohibited by KVM. I think we should keep the
testcase for this model to ensure test coverage?
+1. Deprecated doesn't mean unsupported.
The original test case was for non-in-place conversion, which wasn't
removed, it still passes.
It only passes when
/sys/module/kvm/parameters/gmem_in_place_conversion=n
It fails as below when gmem_in_place_conversion=y
./tools/testing/selftests/kvm/x86/private_mem_conversions_test
Random seed: 0x7eace343
==== Test Assertion Failure ====
x86/private_mem_conversions_test.c:46: mem[i] == pattern
pid=288745 tid=288747 errno=4 - Interrupted system call
1 0x000000000040426a: memcmp_h at private_mem_conversions_test.c:46
2 (inlined by) __test_mem_conversions at
private_mem_conversions_test.c:356
3 0x00007f2ea2c89c01: ?? ??:0
4 0x00007f2ea2d0ec3f: ?? ??:0
Host expected 0xaa at gpa 0x100000000, got 0x0
Is the ask to also test, under kvm_has_gmem_attributes aka
gmem_in_place_conversion, to have guest_memfd used as purely for private
memory and have shared memory taken from somewhere else completely?
I can rephrase the changelog and change the code to clarify that this
patch is meant to specifically test in-place conversion with MMAP, the
intended usage of in-place conversions.
The ask to test gmem for private and something else for shared seems
like a different test that can be added separately, perhaps in a
follow-up series?
I see it as the fix for existing testcase, not another new test. And the
fix is simple:
1. change to use vm_mem_set_memory_attributes() to set memory attribute.
2. pass GUEST_MEMFD_FLAG_INIT_SHARED to create the gmem because this
test expects the initial state of the gfn is shared.
---8<----
diff --git
a/tools/testing/selftests/kvm/x86/private_mem_conversions_test.c
b/tools/testing/selftests/kvm/x86/private_mem_conversions_test.c
index cf50e9a332c5..fbd6c63d21cf 100644
--- a/tools/testing/selftests/kvm/x86/private_mem_conversions_test.c
+++ b/tools/testing/selftests/kvm/x86/private_mem_conversions_test.c
@@ -307,7 +307,7 @@ static void handle_exit_hypercall(struct kvm_vcpu *vcpu)
vm_guest_mem_fallocate(vm, gpa, size, map_shared);
if (set_attributes)
- vm_set_memory_attributes(vm, gpa, size,
+ vm_mem_set_memory_attributes(vm, gpa, size,
map_shared ? 0 :
KVM_MEMORY_ATTRIBUTE_PRIVATE);
run->hypercall.ret = 0;
}
@@ -382,6 +382,7 @@ static void test_mem_conversions(enum
vm_mem_backing_src_type src_type, u32 nr_v
const size_t slot_size = memfd_size / nr_memslots;
struct kvm_vcpu *vcpus[KVM_MAX_VCPUS];
pthread_t threads[KVM_MAX_VCPUS];
+ u64 gmem_flags = 0;
struct kvm_vm *vm;
int memfd, i;
@@ -397,7 +398,10 @@ static void test_mem_conversions(enum
vm_mem_backing_src_type src_type, u32 nr_v
vm_enable_cap(vm, KVM_CAP_EXIT_HYPERCALL, (1 <<
KVM_HC_MAP_GPA_RANGE));
- memfd = vm_create_guest_memfd(vm, memfd_size, 0);
+ if (kvm_has_gmem_attributes)
+ gmem_flags = GUEST_MEMFD_FLAG_INIT_SHARED;
+
+ memfd = vm_create_guest_memfd(vm, memfd_size, gmem_flags);
for (i = 0; i < nr_memslots; i++)
vm_mem_add(vm, src_type, BASE_DATA_GPA + slot_size * i,
