linux-kernel - [PATCH v2 10/13] KVM: selftests: Isolate the guest

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Message-ID: <20251003232606.4070510-11-seanjc@google.com>
Date: Fri,  3 Oct 2025 16:26:03 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Paolo Bonzini <pbonzini@...hat.com>, Sean Christopherson <seanjc@...gle.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>, 
	Ackerley Tng <ackerleytng@...gle.com>
Subject: [PATCH v2 10/13] KVM: selftests: Isolate the guest_memfd
 Copy-on-Write negative testcase

Move the guest_memfd Copy-on-Write (CoW) testcase to its own function to
better separate positive testcases from negative testcases.

No functional change intended.

Suggested-by: Ackerley Tng <ackerleytng@...gle.com>
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 tools/testing/selftests/kvm/guest_memfd_test.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/tools/testing/selftests/kvm/guest_memfd_test.c b/tools/testing/selftests/kvm/guest_memfd_test.c
index 319fda4f5d53..640636c76eb9 100644
--- a/tools/testing/selftests/kvm/guest_memfd_test.c
+++ b/tools/testing/selftests/kvm/guest_memfd_test.c
@@ -40,15 +40,20 @@ static void test_file_read_write(int fd, size_t total_size)
 		    "pwrite on a guest_mem fd should fail");
 }
 
-static void test_mmap_supported(int fd, size_t total_size)
+static void test_mmap_cow(int fd, size_t size)
 {
-	const char val = 0xaa;
-	char *mem;
-	size_t i;
-	int ret;
+	void *mem;
 
-	mem = mmap(NULL, total_size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
+	mem = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
 	TEST_ASSERT(mem == MAP_FAILED, "Copy-on-write not allowed by guest_memfd.");
+}
+
+static void test_mmap_supported(int fd, size_t total_size)
+{
+	const char val = 0xaa;
+	char *mem;
+	size_t i;
+	int ret;
 
 	mem = kvm_mmap(total_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd);
 
@@ -272,6 +277,7 @@ static void __test_guest_memfd(struct kvm_vm *vm, uint64_t flags)
 
 	if (flags & GUEST_MEMFD_FLAG_MMAP) {
 		gmem_test(mmap_supported, vm, flags);
+		gmem_test(mmap_cow, vm, flags);
 		gmem_test(fault_overflow, vm, flags);
 	} else {
 		gmem_test(mmap_not_supported, vm, flags);
-- 
2.51.0.618.g983fd99d29-goog