[RFC,V1,3/5] selftests: kvm: Add a basic selftest to test private memory

diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
index 21c2dbd21a81..f2f9a8546c66 100644
--- a/tools/testing/selftests/kvm/Makefile
+++ b/tools/testing/selftests/kvm/Makefile
@@ -97,6 +97,7 @@  TEST_GEN_PROGS_x86_64 += max_guest_memory_test
 TEST_GEN_PROGS_x86_64 += memslot_modification_stress_test
 TEST_GEN_PROGS_x86_64 += memslot_perf_test
 TEST_GEN_PROGS_x86_64 += rseq_test
+TEST_GEN_PROGS_x86_64 += priv_memfd_test
 TEST_GEN_PROGS_x86_64 += set_memory_region_test
 TEST_GEN_PROGS_x86_64 += steal_time
 TEST_GEN_PROGS_x86_64 += kvm_binary_stats_test
diff --git a/tools/testing/selftests/kvm/priv_memfd_test.c b/tools/testing/selftests/kvm/priv_memfd_test.c
new file mode 100644
index 000000000000..11ccdb853a84
--- /dev/null
+++ b/tools/testing/selftests/kvm/priv_memfd_test.c
@@ -0,0 +1,257 @@ 
+// SPDX-License-Identifier: GPL-2.0
+#define _GNU_SOURCE /* for program_invocation_short_name */
+#include <fcntl.h>
+#include <sched.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/ioctl.h>
+
+#include <linux/compiler.h>
+#include <linux/kernel.h>
+#include <linux/kvm_para.h>
+#include <linux/memfd.h>
+
+#include <test_util.h>
+#include <kvm_util.h>
+#include <processor.h>
+
+#define TEST_MEM_GPA		0xb0000000
+#define TEST_MEM_SIZE		0x2000
+#define TEST_MEM_END		(TEST_MEM_GPA + TEST_MEM_SIZE)
+#define SHARED_MEM_DATA_BYTE	0x66
+#define PRIV_MEM_DATA_BYTE	0x99
+
+#define TEST_MEM_SLOT		10
+
+#define VCPU_ID			0
+
+#define VM_STAGE_PROCESSED(x)	pr_info("Processed stage %s\n", #x)
+
+typedef bool (*vm_stage_handler_fn)(struct kvm_vm *,
+				void *, uint64_t);
+typedef void (*guest_code_fn)(void);
+struct test_run_helper {
+	char *test_desc;
+	vm_stage_handler_fn vmst_handler;
+	guest_code_fn guest_fn;
+	void *shared_mem;
+	int priv_memfd;
+};
+
+static bool verify_byte_pattern(void *mem, uint8_t byte, uint32_t size)
+{
+	uint8_t *buf = (uint8_t *)mem;
+
+	for (uint32_t i = 0; i < size; i++) {
+		if (buf[i] != byte)
+			return false;
+	}
+
+	return true;
+}
+
+/* Test to verify guest private 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 writes a different pattern on the private memory and signals VMM
+ *      that it has updated private memory.
+ * 4) VMM verifies its shared memory contents to be same as the data populated
+ *      in step 2 and continues guest execution.
+ * 5) Guest verifies its private memory contents to be same as the data
+ *      populated in step 3 and marks the end of the guest execution.
+ */
+#define PMPAT_ID				0
+#define PMPAT_DESC				"PrivateMemoryPrivateAccessTest"
+
+/* Guest code execution stages for private mem access test */
+#define PMPAT_GUEST_STARTED			0ULL
+#define PMPAT_GUEST_PRIV_MEM_UPDATED		1ULL
+
+static bool pmpat_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 PMPAT_GUEST_STARTED: {
+		/* Initialize the contents of shared memory */
+		memset(shared_mem, SHARED_MEM_DATA_BYTE, TEST_MEM_SIZE);
+		VM_STAGE_PROCESSED(PMPAT_GUEST_STARTED);
+		break;
+	}
+	case PMPAT_GUEST_PRIV_MEM_UPDATED: {
+		/* verify host updated data is still intact */
+		TEST_ASSERT(verify_byte_pattern(shared_mem,
+			SHARED_MEM_DATA_BYTE, TEST_MEM_SIZE),
+			"Shared memory view mismatch");
+		VM_STAGE_PROCESSED(PMPAT_GUEST_PRIV_MEM_UPDATED);
+		break;
+	}
+	default:
+		printf("Unhandled VM stage %ld\n", stage);
+		return false;
+	}
+
+	return true;
+}
+
+static void pmpat_guest_code(void)
+{
+	void *priv_mem = (void *)TEST_MEM_GPA;
+	int ret;
+
+	GUEST_SYNC(PMPAT_GUEST_STARTED);
+
+	/* Mark the GPA range to be treated as always accessed privately */
+	ret = kvm_hypercall(KVM_HC_MAP_GPA_RANGE, TEST_MEM_GPA,
+		TEST_MEM_SIZE >> MIN_PAGE_SHIFT,
+		KVM_MARK_GPA_RANGE_ENC_ACCESS, 0);
+	GUEST_ASSERT_1(ret == 0, ret);
+
+	memset(priv_mem, PRIV_MEM_DATA_BYTE, TEST_MEM_SIZE);
+	GUEST_SYNC(PMPAT_GUEST_PRIV_MEM_UPDATED);
+
+	GUEST_ASSERT(verify_byte_pattern(priv_mem,
+			PRIV_MEM_DATA_BYTE, TEST_MEM_SIZE));
+
+	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,
+	},
+};
+
+static void vcpu_work(struct kvm_vm *vm, uint32_t test_id)
+{
+	struct kvm_run *run;
+	struct ucall uc;
+	uint64_t cmd;
+
+	/*
+	 * Loop until the guest is done.
+	 */
+	run = vcpu_state(vm, VCPU_ID);
+
+	while (true) {
+		vcpu_run(vm, VCPU_ID);
+
+		if (run->exit_reason == KVM_EXIT_IO) {
+			cmd = get_ucall(vm, VCPU_ID, &uc);
+			if (cmd != UCALL_SYNC)
+				break;
+
+			if (!priv_memfd_testsuite[test_id].vmst_handler(
+				vm, &priv_memfd_testsuite[test_id], uc.args[1]))
+				break;
+
+			continue;
+		}
+
+		TEST_FAIL("Unhandled VCPU exit reason %d\n", run->exit_reason);
+		break;
+	}
+
+	if (run->exit_reason == KVM_EXIT_IO && cmd == UCALL_ABORT)
+		TEST_FAIL("%s at %s:%ld, val = %lu", (const char *)uc.args[0],
+			  __FILE__, uc.args[1], uc.args[2]);
+}
+
+static void priv_memory_region_add(struct kvm_vm *vm, void *mem, uint32_t slot,
+				uint32_t size, uint64_t guest_addr,
+				uint32_t priv_fd, uint64_t priv_offset)
+{
+	struct kvm_userspace_memory_region_ext region_ext;
+	int ret;
+
+	region_ext.region.slot = slot;
+	region_ext.region.flags = KVM_MEM_PRIVATE;
+	region_ext.region.guest_phys_addr = guest_addr;
+	region_ext.region.memory_size = size;
+	region_ext.region.userspace_addr = (uintptr_t) mem;
+	region_ext.private_fd = priv_fd;
+	region_ext.private_offset = priv_offset;
+	ret = ioctl(vm_get_fd(vm), KVM_SET_USER_MEMORY_REGION, &region_ext);
+	TEST_ASSERT(ret == 0, "Failed to register user region for gpa 0x%lx\n",
+		guest_addr);
+}
+
+/* Do private access to the guest's private memory */
+static void setup_and_execute_test(uint32_t test_id)
+{
+	struct kvm_vm *vm;
+	int priv_memfd;
+	int ret;
+	void *shared_mem;
+	struct kvm_enable_cap cap;
+
+	vm = vm_create_default(VCPU_ID, 0,
+				priv_memfd_testsuite[test_id].guest_fn);
+
+	/* Allocate shared memory */
+	shared_mem = mmap(NULL, TEST_MEM_SIZE,
+			PROT_READ | PROT_WRITE,
+			MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE, -1, 0);
+	TEST_ASSERT(shared_mem != MAP_FAILED, "Failed to mmap() host");
+
+	/* Allocate private memory */
+	priv_memfd = memfd_create("vm_private_mem", MFD_INACCESSIBLE);
+	TEST_ASSERT(priv_memfd != -1, "Failed to create priv_memfd");
+	ret = fallocate(priv_memfd, 0, 0, TEST_MEM_SIZE);
+	TEST_ASSERT(ret != -1, "fallocate failed");
+
+	priv_memory_region_add(vm, shared_mem,
+				TEST_MEM_SLOT, TEST_MEM_SIZE,
+				TEST_MEM_GPA, priv_memfd, 0);
+
+	pr_info("Mapping test memory pages 0x%x page_size 0x%x\n",
+					TEST_MEM_SIZE/vm_get_page_size(vm),
+					vm_get_page_size(vm));
+	virt_map(vm, TEST_MEM_GPA, TEST_MEM_GPA,
+					(TEST_MEM_SIZE/vm_get_page_size(vm)));
+
+	/* Enable exit on KVM_HC_MAP_GPA_RANGE */
+	pr_info("Enabling exit on map_gpa_range hypercall\n");
+	ret = ioctl(vm_get_fd(vm), KVM_CHECK_EXTENSION, KVM_CAP_EXIT_HYPERCALL);
+	TEST_ASSERT(ret & (1 << KVM_HC_MAP_GPA_RANGE),
+				"VM exit on MAP_GPA_RANGE HC not supported");
+	cap.cap = KVM_CAP_EXIT_HYPERCALL;
+	cap.flags = 0;
+	cap.args[0] = (1 << KVM_HC_MAP_GPA_RANGE);
+	ret = ioctl(vm_get_fd(vm), KVM_ENABLE_CAP, &cap);
+	TEST_ASSERT(ret == 0,
+		"Failed to enable exit on MAP_GPA_RANGE hypercall\n");
+
+	priv_memfd_testsuite[test_id].shared_mem = shared_mem;
+	priv_memfd_testsuite[test_id].priv_memfd = priv_memfd;
+	vcpu_work(vm, test_id);
+
+	munmap(shared_mem, TEST_MEM_SIZE);
+	priv_memfd_testsuite[test_id].shared_mem = NULL;
+	close(priv_memfd);
+	priv_memfd_testsuite[test_id].priv_memfd = -1;
+	kvm_vm_free(vm);
+}
+
+int main(int argc, char *argv[])
+{
+	/* Tell stdout not to buffer its content */
+	setbuf(stdout, NULL);
+
+	for (uint32_t i = 0; i < ARRAY_SIZE(priv_memfd_testsuite); i++) {
+		pr_info("=== Starting test %s... ===\n",
+				priv_memfd_testsuite[i].test_desc);
+		setup_and_execute_test(i);
+		pr_info("--- completed test %s ---\n\n",
+				priv_memfd_testsuite[i].test_desc);
+	}
+
+	return 0;
+}