[RFC V1 PATCH 5/5] selftests: kvm: priv_memfd_test: Add shared access test

[Vishal Annapurve <vannapurve@google.com>]

Add a test to access private memory in shared fashion
which should exercise implicit memory conversion path
using KVM_EXIT_MEMORY_ERROR.

Signed-off-by: Vishal Annapurve <vannapurve@google.com>
---
 tools/testing/selftests/kvm/priv_memfd_test.c | 66 +++++++++++++++++++
 1 file changed, 66 insertions(+)

diff --git a/tools/testing/selftests/kvm/priv_memfd_test.c b/tools/testing/selftests/kvm/priv_memfd_test.c
index 0e6c19501f27..607fdc149c7d 100644
--- a/tools/testing/selftests/kvm/priv_memfd_test.c
+++ b/tools/testing/selftests/kvm/priv_memfd_test.c
@@ -121,12 +121,78 @@ static void pmpat_guest_code(void)
 	GUEST_DONE();
 }
 
+/* Test to verify guest shared accesses on private memory with following steps:
+ * 1) Upon entry, guest signals VMM that it has started.
+ * 2) VMM populates the shared memory with known pattern and continues guest
+ *    execution.
+ * 3) Guest reads private gpa range in a shared fashion and verifies that it
+ *    reads what VMM has written in step2.
+ * 3) Guest writes a different pattern on the shared memory and signals VMM
+ *      that it has updated the shared memory.
+ * 4) VMM verifies shared memory contents to be same as the data populated
+ *      in step 3 and continues guest execution.
+ */
+#define PMSAT_ID				1
+#define PMSAT_DESC				"PrivateMemorySharedAccessTest"
+
+/* Guest code execution stages for private mem access test */
+#define PMSAT_GUEST_STARTED			0ULL
+#define PMSAT_GUEST_TEST_MEM_UPDATED		1ULL
+
+static bool pmsat_handle_vm_stage(struct kvm_vm *vm,
+			void *test_info,
+			uint64_t stage)
+{
+	void *shared_mem = ((struct test_run_helper *)test_info)->shared_mem;
+
+	switch (stage) {
+	case PMSAT_GUEST_STARTED: {
+		/* Initialize the contents of shared memory */
+		memset(shared_mem, SHARED_MEM_DATA_BYTE, TEST_MEM_SIZE);
+		VM_STAGE_PROCESSED(PMSAT_GUEST_STARTED);
+		break;
+	}
+	case PMSAT_GUEST_TEST_MEM_UPDATED: {
+		/* verify data to be same as what guest wrote */
+		TEST_ASSERT(verify_byte_pattern(shared_mem,
+			PRIV_MEM_DATA_BYTE, TEST_MEM_SIZE),
+			"Shared memory view mismatch");
+		VM_STAGE_PROCESSED(PMSAT_GUEST_PRIV_MEM_UPDATED);
+		break;
+	}
+	default:
+		printf("Unhandled VM stage %ld\n", stage);
+		return false;
+	}
+
+	return true;
+}
+
+static void pmsat_guest_code(void)
+{
+	void *shared_mem = (void *)TEST_MEM_GPA;
+
+	GUEST_SYNC(PMSAT_GUEST_STARTED);
+	GUEST_ASSERT(verify_byte_pattern(shared_mem,
+			SHARED_MEM_DATA_BYTE, TEST_MEM_SIZE));
+
+	memset(shared_mem, PRIV_MEM_DATA_BYTE, TEST_MEM_SIZE);
+	GUEST_SYNC(PMSAT_GUEST_TEST_MEM_UPDATED);
+
+	GUEST_DONE();
+}
+
 static struct test_run_helper priv_memfd_testsuite[] = {
 	[PMPAT_ID] = {
 		.test_desc = PMPAT_DESC,
 		.vmst_handler = pmpat_handle_vm_stage,
 		.guest_fn = pmpat_guest_code,
 	},
+	[PMSAT_ID] = {
+		.test_desc = PMSAT_DESC,
+		.vmst_handler = pmsat_handle_vm_stage,
+		.guest_fn = pmsat_guest_code,
+	},
 };
 
 static void handle_vm_exit_hypercall(struct kvm_run *run,
-- 
2.35.1.1178.g4f1659d476-goog