KVM: selftests: x86: Add test for KVM_PRE_FAULT_MEMORY

Add a test case to exercise KVM_PRE_FAULT_MEMORY and run the guest to access the
pre-populated area.  It tests KVM_PRE_FAULT_MEMORY ioctl for KVM_X86_DEFAULT_VM
and KVM_X86_SW_PROTECTED_VM.
Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
Message-ID: <32427791ef42e5efaafb05d2ac37fa4372715f47.1712785629.git.isaku.yamahata@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

tools/include/uapi/linux/kvm.h

@@ -917,6 +917,7 @@ struct kvm_enable_cap {
 #define KVM_CAP_MEMORY_ATTRIBUTES 233
 #define KVM_CAP_GUEST_MEMFD 234
 #define KVM_CAP_VM_TYPES 235
+#define KVM_CAP_PRE_FAULT_MEMORY 236
 
 struct kvm_irq_routing_irqchip {
 	__u32 irqchip;
@@ -1221,9 +1222,9 @@ struct kvm_vfio_spapr_tce {
 /* Available with KVM_CAP_SPAPR_RESIZE_HPT */
 #define KVM_PPC_RESIZE_HPT_PREPARE _IOR(KVMIO, 0xad, struct kvm_ppc_resize_hpt)
 #define KVM_PPC_RESIZE_HPT_COMMIT  _IOR(KVMIO, 0xae, struct kvm_ppc_resize_hpt)
-/* Available with KVM_CAP_PPC_RADIX_MMU or KVM_CAP_PPC_MMU_HASH_V3 */
+/* Available with KVM_CAP_PPC_MMU_RADIX or KVM_CAP_PPC_MMU_HASH_V3 */
 #define KVM_PPC_CONFIGURE_V3_MMU  _IOW(KVMIO,  0xaf, struct kvm_ppc_mmuv3_cfg)
-/* Available with KVM_CAP_PPC_RADIX_MMU */
+/* Available with KVM_CAP_PPC_MMU_RADIX */
 #define KVM_PPC_GET_RMMU_INFO	  _IOW(KVMIO,  0xb0, struct kvm_ppc_rmmu_info)
 /* Available with KVM_CAP_PPC_GET_CPU_CHAR */
 #define KVM_PPC_GET_CPU_CHAR	  _IOR(KVMIO,  0xb1, struct kvm_ppc_cpu_char)
@@ -1548,4 +1549,13 @@ struct kvm_create_guest_memfd {
 	__u64 reserved[6];
 };
 
+#define KVM_PRE_FAULT_MEMORY	_IOWR(KVMIO, 0xd5, struct kvm_pre_fault_memory)
+
+struct kvm_pre_fault_memory {
+	__u64 gpa;
+	__u64 size;
+	__u64 flags;
+	__u64 padding[5];
+};
+
 #endif /* __LINUX_KVM_H */

tools/testing/selftests/kvm/Makefile

@@ -145,6 +145,7 @@ 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
 TEST_GEN_PROGS_x86_64 += system_counter_offset_test
+TEST_GEN_PROGS_x86_64 += pre_fault_memory_test
 
 # Compiled outputs used by test targets
 TEST_GEN_PROGS_EXTENDED_x86_64 += x86_64/nx_huge_pages_test

tools/testing/selftests/kvm/pre_fault_memory_test.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2024, Intel, Inc
+ *
+ * Author:
+ * Isaku Yamahata <isaku.yamahata at gmail.com>
+ */
+#include <linux/sizes.h>
+
+#include <test_util.h>
+#include <kvm_util.h>
+#include <processor.h>
+
+/* Arbitrarily chosen values */
+#define TEST_SIZE		(SZ_2M + PAGE_SIZE)
+#define TEST_NPAGES		(TEST_SIZE / PAGE_SIZE)
+#define TEST_SLOT		10
+
+static void guest_code(uint64_t base_gpa)
+{
+	volatile uint64_t val __used;
+	int i;
+
+	for (i = 0; i < TEST_NPAGES; i++) {
+		uint64_t *src = (uint64_t *)(base_gpa + i * PAGE_SIZE);
+
+		val = *src;
+	}
+
+	GUEST_DONE();
+}
+
+static void pre_fault_memory(struct kvm_vcpu *vcpu, u64 gpa, u64 size,
+			     u64 left)
+{
+	struct kvm_pre_fault_memory range = {
+		.gpa = gpa,
+		.size = size,
+		.flags = 0,
+	};
+	u64 prev;
+	int ret, save_errno;
+
+	do {
+		prev = range.size;
+		ret = __vcpu_ioctl(vcpu, KVM_PRE_FAULT_MEMORY, &range);
+		save_errno = errno;
+		TEST_ASSERT((range.size < prev) ^ (ret < 0),
+			    "%sexpecting range.size to change on %s",
+			    ret < 0 ? "not " : "",
+			    ret < 0 ? "failure" : "success");
+	} while (ret >= 0 ? range.size : save_errno == EINTR);
+
+	TEST_ASSERT(range.size == left,
+		    "Completed with %lld bytes left, expected %" PRId64,
+		    range.size, left);
+
+	if (left == 0)
+		__TEST_ASSERT_VM_VCPU_IOCTL(!ret, "KVM_PRE_FAULT_MEMORY", ret, vcpu->vm);
+	else
+		/* No memory slot causes RET_PF_EMULATE. it results in -ENOENT. */
+		__TEST_ASSERT_VM_VCPU_IOCTL(ret && save_errno == ENOENT,
+					    "KVM_PRE_FAULT_MEMORY", ret, vcpu->vm);
+}
+
+static void __test_pre_fault_memory(unsigned long vm_type, bool private)
+{
+	const struct vm_shape shape = {
+		.mode = VM_MODE_DEFAULT,
+		.type = vm_type,
+	};
+	struct kvm_vcpu *vcpu;
+	struct kvm_run *run;
+	struct kvm_vm *vm;
+	struct ucall uc;
+
+	uint64_t guest_test_phys_mem;
+	uint64_t guest_test_virt_mem;
+	uint64_t alignment, guest_page_size;
+
+	vm = vm_create_shape_with_one_vcpu(shape, &vcpu, guest_code);
+
+	alignment = guest_page_size = vm_guest_mode_params[VM_MODE_DEFAULT].page_size;
+	guest_test_phys_mem = (vm->max_gfn - TEST_NPAGES) * guest_page_size;
+#ifdef __s390x__
+	alignment = max(0x100000UL, guest_page_size);
+#else
+	alignment = SZ_2M;
+#endif
+	guest_test_phys_mem = align_down(guest_test_phys_mem, alignment);
+	guest_test_virt_mem = guest_test_phys_mem & ((1ULL << (vm->va_bits - 1)) - 1);
+
+	vm_userspace_mem_region_add(vm, VM_MEM_SRC_ANONYMOUS,
+				    guest_test_phys_mem, TEST_SLOT, TEST_NPAGES,
+				    private ? KVM_MEM_GUEST_MEMFD : 0);
+	virt_map(vm, guest_test_virt_mem, guest_test_phys_mem, TEST_NPAGES);
+
+	if (private)
+		vm_mem_set_private(vm, guest_test_phys_mem, TEST_SIZE);
+	pre_fault_memory(vcpu, guest_test_phys_mem, SZ_2M, 0);
+	pre_fault_memory(vcpu, guest_test_phys_mem + SZ_2M, PAGE_SIZE * 2, PAGE_SIZE);
+	pre_fault_memory(vcpu, guest_test_phys_mem + TEST_SIZE, PAGE_SIZE, PAGE_SIZE);
+
+	vcpu_args_set(vcpu, 1, guest_test_virt_mem);
+	vcpu_run(vcpu);
+
+	run = vcpu->run;
+	TEST_ASSERT(run->exit_reason == KVM_EXIT_IO,
+		    "Wanted KVM_EXIT_IO, got exit reason: %u (%s)",
+		    run->exit_reason, exit_reason_str(run->exit_reason));
+
+	switch (get_ucall(vcpu, &uc)) {
+	case UCALL_ABORT:
+		REPORT_GUEST_ASSERT(uc);
+		break;
+	case UCALL_DONE:
+		break;
+	default:
+		TEST_FAIL("Unknown ucall 0x%lx.", uc.cmd);
+		break;
+	}
+
+	kvm_vm_free(vm);
+}
+
+static void test_pre_fault_memory(unsigned long vm_type, bool private)
+{
+	if (vm_type && !(kvm_check_cap(KVM_CAP_VM_TYPES) & BIT(vm_type))) {
+		pr_info("Skipping tests for vm_type 0x%lx\n", vm_type);
+		return;
+	}
+
+	__test_pre_fault_memory(vm_type, private);
+}
+
+int main(int argc, char *argv[])
+{
+	TEST_REQUIRE(kvm_check_cap(KVM_CAP_PRE_FAULT_MEMORY));
+
+	test_pre_fault_memory(0, false);
+#ifdef __x86_64__
+	test_pre_fault_memory(KVM_X86_SW_PROTECTED_VM, false);
+	test_pre_fault_memory(KVM_X86_SW_PROTECTED_VM, true);
+#endif
+	return 0;
+}