[PATCH RFC v3 7/7] KVM: selftests: Test guest_memfd behavior with respect to stage 2 page tables

[Lisa Wang <wyihan@google.com>]

Test that
+ memory failure handling results in unmapping of bad memory from stage
  2 page tables, hence requiring faulting on next guest access
+ when the guest tries to fault a poisoned page from guest_memfd, the
  userspace VMM informed with EHWPOISON

Co-developed-by: Ackerley Tng <ackerleytng@google.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
Signed-off-by: Lisa Wang <wyihan@google.com>
---
 tools/testing/selftests/kvm/guest_memfd_test.c | 70 +++++++++++++++++++++++++-
 1 file changed, 69 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/kvm/guest_memfd_test.c b/tools/testing/selftests/kvm/guest_memfd_test.c
index 0ea4e7d7e6d5..6615ee8bfcd8 100644
--- a/tools/testing/selftests/kvm/guest_memfd_test.c
+++ b/tools/testing/selftests/kvm/guest_memfd_test.c
@@ -26,6 +26,7 @@
 #include "ucall_common.h"
 
 static size_t page_size;
+static uint64_t test_memory_failure_guest_gpa;
 
 static void test_file_read_write(int fd, size_t total_size)
 {
@@ -637,6 +638,73 @@ static void test_guest_memfd_guest(void)
 	kvm_vm_free(vm);
 }
 
+static void __guest_code_read(void)
+{
+	uint8_t *mem = (uint8_t *)test_memory_failure_guest_gpa;
+
+	READ_ONCE(*mem);
+	GUEST_SYNC(0);
+	READ_ONCE(*mem);
+	GUEST_DONE();
+}
+
+static void guest_read(struct kvm_vcpu *vcpu, int expected_errno)
+{
+	if (expected_errno) {
+		TEST_ASSERT_EQ(_vcpu_run(vcpu), -1);
+		TEST_ASSERT_EQ(errno, expected_errno);
+	} else {
+		vcpu_run(vcpu);
+		TEST_ASSERT_EQ(get_ucall(vcpu, NULL), UCALL_SYNC);
+	}
+}
+
+static void test_memory_failure_guest(void)
+{
+	const uint64_t gpa = SZ_4G;
+	const int slot = 1;
+
+	unsigned long memory_failure_pfn;
+	struct kvm_vcpu *vcpu;
+	struct kvm_vm *vm;
+	uint8_t *mem;
+	size_t size;
+	int fd;
+
+	if (!kvm_has_cap(KVM_CAP_GUEST_MEMFD_FLAGS))
+		return;
+
+	vm = __vm_create_shape_with_one_vcpu(VM_SHAPE_DEFAULT, &vcpu, 1, __guest_code_read);
+
+	size = vm->page_size;
+	fd = vm_create_guest_memfd(vm, size, GUEST_MEMFD_FLAG_MMAP | GUEST_MEMFD_FLAG_INIT_SHARED);
+	vm_set_user_memory_region2(vm, slot, KVM_MEM_GUEST_MEMFD, gpa, size, NULL, fd, 0);
+
+	mem = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
+	TEST_ASSERT(mem != MAP_FAILED, "mmap() for guest_memfd should succeed.");
+	virt_pg_map(vm, gpa, gpa);
+
+	test_memory_failure_guest_gpa = gpa;
+	sync_global_to_guest(vm, test_memory_failure_guest_gpa);
+
+	/* Fault in page to read pfn, then unmap page for testing. */
+	READ_ONCE(*mem);
+	memory_failure_pfn = addr_to_pfn(mem);
+	munmap(mem, size);
+
+	/* Fault page into stage2 page tables. */
+	guest_read(vcpu, 0);
+
+	mark_memory_failure(memory_failure_pfn, 0);
+
+	guest_read(vcpu, EHWPOISON);
+
+	close(fd);
+	kvm_vm_free(vm);
+
+	unmark_memory_failure(memory_failure_pfn, 0);
+}
+
 int main(int argc, char *argv[])
 {
 	unsigned long vm_types, vm_type;
@@ -644,7 +712,6 @@ int main(int argc, char *argv[])
 	TEST_REQUIRE(kvm_has_cap(KVM_CAP_GUEST_MEMFD));
 
 	page_size = getpagesize();
-
 	/*
 	 * Not all architectures support KVM_CAP_VM_TYPES. However, those that
 	 * support guest_memfd have that support for the default VM type.
@@ -657,4 +724,5 @@ int main(int argc, char *argv[])
 		test_guest_memfd(vm_type);
 
 	test_guest_memfd_guest();
+	test_memory_failure_guest();
 }

-- 
2.53.0.1213.gd9a14994de-goog