linux-kernel - [PATCH 4/6] KVM: selftests: Add test coverage for guest_memfd without GUEST_MEMFD_FLAG

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Message-ID: <20250926163114.2626257-5-seanjc@google.com>
Date: Fri, 26 Sep 2025 09:31:05 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Paolo Bonzini <pbonzini@...hat.com>, Christian Borntraeger <borntraeger@...ux.ibm.com>, 
	Janosch Frank <frankja@...ux.ibm.com>, Claudio Imbrenda <imbrenda@...ux.ibm.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	David Hildenbrand <david@...hat.com>, Fuad Tabba <tabba@...gle.com>, 
	Sean Christopherson <seanjc@...gle.com>, Ackerley Tng <ackerleytng@...gle.com>
Subject: [PATCH 4/6] KVM: selftests: Add test coverage for guest_memfd without GUEST_MEMFD_FLAG_MMAP

From: Ackerley Tng <ackerleytng@...gle.com>

If a VM type supports KVM_CAP_GUEST_MEMFD_MMAP, the guest_memfd test will
run all test cases with GUEST_MEMFD_FLAG_MMAP set.  This leaves the code
path for creating a non-mmap()-able guest_memfd on a VM that supports
mappable guest memfds untested.

Refactor the test to run the main test suite with a given set of flags.
Then, for VM types that support the mappable capability, invoke the test
suite twice: once with no flags, and once with GUEST_MEMFD_FLAG_MMAP
set.

This ensures both creation paths are properly exercised on capable VMs.

test_guest_memfd_flags() tests valid flags, hence it can be run just once
per VM type, and valid flag identification can be moved into the test
function.

Signed-off-by: Ackerley Tng <ackerleytng@...gle.com>
[sean: use double-underscores for the inner helper]
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 .../testing/selftests/kvm/guest_memfd_test.c  | 30 ++++++++++++-------
 1 file changed, 19 insertions(+), 11 deletions(-)

diff --git a/tools/testing/selftests/kvm/guest_memfd_test.c b/tools/testing/selftests/kvm/guest_memfd_test.c
index 60c6dec63490..5a50a28ce1fa 100644
--- a/tools/testing/selftests/kvm/guest_memfd_test.c
+++ b/tools/testing/selftests/kvm/guest_memfd_test.c
@@ -239,11 +239,16 @@ static void test_create_guest_memfd_multiple(struct kvm_vm *vm)
 	close(fd1);
 }
 
-static void test_guest_memfd_flags(struct kvm_vm *vm, uint64_t valid_flags)
+static void test_guest_memfd_flags(struct kvm_vm *vm)
 {
+	uint64_t valid_flags = 0;
 	uint64_t flag;
 	int fd;
 
+	if (vm_check_cap(vm, KVM_CAP_GUEST_MEMFD_MMAP))
+		valid_flags |= GUEST_MEMFD_FLAG_MMAP |
+			       GUEST_MEMFD_FLAG_DEFAULT_SHARED;
+
 	for (flag = BIT(0); flag; flag <<= 1) {
 		fd = __vm_create_guest_memfd(vm, page_size, flag);
 		if (flag & valid_flags) {
@@ -267,16 +272,8 @@ do {									\
 	close(fd);							\
 } while (0)
 
-static void test_guest_memfd(unsigned long vm_type)
+static void __test_guest_memfd(struct kvm_vm *vm, uint64_t flags)
 {
-	uint64_t flags = 0;
-	struct kvm_vm *vm;
-
-	vm = vm_create_barebones_type(vm_type);
-
-	if (vm_check_cap(vm, KVM_CAP_GUEST_MEMFD_MMAP))
-		flags |= GUEST_MEMFD_FLAG_MMAP | GUEST_MEMFD_FLAG_DEFAULT_SHARED;
-
 	test_create_guest_memfd_multiple(vm);
 	test_create_guest_memfd_invalid_sizes(vm, flags);
 
@@ -292,8 +289,19 @@ static void test_guest_memfd(unsigned long vm_type)
 	gmem_test(file_size, vm, flags);
 	gmem_test(fallocate, vm, flags);
 	gmem_test(invalid_punch_hole, vm, flags);
+}
 
-	test_guest_memfd_flags(vm, flags);
+static void test_guest_memfd(unsigned long vm_type)
+{
+	struct kvm_vm *vm = vm_create_barebones_type(vm_type);
+
+	test_guest_memfd_flags(vm);
+
+	__test_guest_memfd(vm, 0);
+
+	if (vm_check_cap(vm, KVM_CAP_GUEST_MEMFD_MMAP))
+		__test_guest_memfd(vm, GUEST_MEMFD_FLAG_MMAP |
+				       GUEST_MEMFD_FLAG_DEFAULT_SHARED);
 
 	kvm_vm_free(vm);
 }
-- 
2.51.0.536.g15c5d4f767-goog