1 files changed, 426 insertions, 0 deletions
diff --git a/tools/testing/selftests/kvm/mmu_stress_test.c b/tools/testing/selftests/kvm/mmu_stress_test.c
new file mode 100644
index 000000000000..6a437d2be9fa
--- /dev/null
+++ b/tools/testing/selftests/kvm/mmu_stress_test.c
@@ -0,0 +1,426 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <stdio.h>
+#include <stdlib.h>
+#include <pthread.h>
+#include <semaphore.h>
+#include <sys/types.h>
+#include <signal.h>
+#include <errno.h>
+#include <linux/bitmap.h>
+#include <linux/bitops.h>
+#include <linux/atomic.h>
+#include <linux/sizes.h>
+
+#include "kvm_util.h"
+#include "test_util.h"
+#include "guest_modes.h"
+#include "processor.h"
+#include "ucall_common.h"
+
+static bool mprotect_ro_done;
+static bool all_vcpus_hit_ro_fault;
+
+static void guest_code(uint64_t start_gpa, uint64_t end_gpa, uint64_t stride)
+{
+	uint64_t gpa;
+	int i;
+
+	for (i = 0; i < 2; i++) {
+		for (gpa = start_gpa; gpa < end_gpa; gpa += stride)
+			vcpu_arch_put_guest(*((volatile uint64_t *)gpa), gpa);
+		GUEST_SYNC(i);
+	}
+
+	for (gpa = start_gpa; gpa < end_gpa; gpa += stride)
+		*((volatile uint64_t *)gpa);
+	GUEST_SYNC(2);
+
+	/*
+	 * Write to the region while mprotect(PROT_READ) is underway.  Keep
+	 * looping until the memory is guaranteed to be read-only and a fault
+	 * has occurred, otherwise vCPUs may complete their writes and advance
+	 * to the next stage prematurely.
+	 *
+	 * For architectures that support skipping the faulting instruction,
+	 * generate the store via inline assembly to ensure the exact length
+	 * of the instruction is known and stable (vcpu_arch_put_guest() on
+	 * fixed-length architectures should work, but the cost of paranoia
+	 * is low in this case).  For x86, hand-code the exact opcode so that
+	 * there is no room for variability in the generated instruction.
+	 */
+	do {
+		for (gpa = start_gpa; gpa < end_gpa; gpa += stride)
+#ifdef __x86_64__
+			asm volatile(".byte 0x48,0x89,0x00" :: "a"(gpa) : "memory"); /* mov %rax, (%rax) */
+#elif defined(__aarch64__)
+			asm volatile("str %0, [%0]" :: "r" (gpa) : "memory");
+#else
+			vcpu_arch_put_guest(*((volatile uint64_t *)gpa), gpa);
+#endif
+	} while (!READ_ONCE(mprotect_ro_done) || !READ_ONCE(all_vcpus_hit_ro_fault));
+
+	/*
+	 * Only architectures that write the entire range can explicitly sync,
+	 * as other architectures will be stuck on the write fault.
+	 */
+#if defined(__x86_64__) || defined(__aarch64__)
+	GUEST_SYNC(3);
+#endif
+
+	for (gpa = start_gpa; gpa < end_gpa; gpa += stride)
+		vcpu_arch_put_guest(*((volatile uint64_t *)gpa), gpa);
+	GUEST_SYNC(4);
+
+	GUEST_ASSERT(0);
+}
+
+struct vcpu_info {
+	struct kvm_vcpu *vcpu;
+	uint64_t start_gpa;
+	uint64_t end_gpa;
+};
+
+static int nr_vcpus;
+static atomic_t rendezvous;
+static atomic_t nr_ro_faults;
+
+static void rendezvous_with_boss(void)
+{
+	int orig = atomic_read(&rendezvous);
+
+	if (orig > 0) {
+		atomic_dec_and_test(&rendezvous);
+		while (atomic_read(&rendezvous) > 0)
+			cpu_relax();
+	} else {
+		atomic_inc(&rendezvous);
+		while (atomic_read(&rendezvous) < 0)
+			cpu_relax();
+	}
+}
+
+static void assert_sync_stage(struct kvm_vcpu *vcpu, int stage)
+{
+	struct ucall uc;
+
+	TEST_ASSERT_EQ(get_ucall(vcpu, &uc), UCALL_SYNC);
+	TEST_ASSERT_EQ(uc.args[1], stage);
+}
+
+static void run_vcpu(struct kvm_vcpu *vcpu, int stage)
+{
+	vcpu_run(vcpu);
+	assert_sync_stage(vcpu, stage);
+}
+
+static void *vcpu_worker(void *data)
+{
+	struct kvm_sregs __maybe_unused sregs;
+	struct vcpu_info *info = data;
+	struct kvm_vcpu *vcpu = info->vcpu;
+	struct kvm_vm *vm = vcpu->vm;
+	int r;
+
+	vcpu_args_set(vcpu, 3, info->start_gpa, info->end_gpa, vm->page_size);
+
+	rendezvous_with_boss();
+
+	/* Stage 0, write all of guest memory. */
+	run_vcpu(vcpu, 0);
+	rendezvous_with_boss();
+#ifdef __x86_64__
+	vcpu_sregs_get(vcpu, &sregs);
+	/* Toggle CR0.WP to trigger a MMU context reset. */
+	sregs.cr0 ^= X86_CR0_WP;
+	vcpu_sregs_set(vcpu, &sregs);
+#endif
+	rendezvous_with_boss();
+
+	/* Stage 1, re-write all of guest memory. */
+	run_vcpu(vcpu, 1);
+	rendezvous_with_boss();
+
+	/* Stage 2, read all of guest memory, which is now read-only. */
+	run_vcpu(vcpu, 2);
+
+	/*
+	 * Stage 3, write guest memory and verify KVM returns -EFAULT for once
+	 * the mprotect(PROT_READ) lands.  Only architectures that support
+	 * validating *all* of guest memory sync for this stage, as vCPUs will
+	 * be stuck on the faulting instruction for other architectures.  Go to
+	 * stage 3 without a rendezvous
+	 */
+	r = _vcpu_run(vcpu);
+	TEST_ASSERT(r == -1 && errno == EFAULT,
+		    "Expected EFAULT on write to RO memory, got r = %d, errno = %d", r, errno);
+
+	atomic_inc(&nr_ro_faults);
+	if (atomic_read(&nr_ro_faults) == nr_vcpus) {
+		WRITE_ONCE(all_vcpus_hit_ro_fault, true);
+		sync_global_to_guest(vm, all_vcpus_hit_ro_fault);
+	}
+
+#if defined(__x86_64__) || defined(__aarch64__)
+	/*
+	 * Verify *all* writes from the guest hit EFAULT due to the VMA now
+	 * being read-only.  x86 and arm64 only at this time as skipping the
+	 * instruction that hits the EFAULT requires advancing the program
+	 * counter, which is arch specific and relies on inline assembly.
+	 */
+#ifdef __x86_64__
+	vcpu->run->kvm_valid_regs = KVM_SYNC_X86_REGS;
+#endif
+	for (;;) {
+		r = _vcpu_run(vcpu);
+		if (!r)
+			break;
+		TEST_ASSERT_EQ(errno, EFAULT);
+#if defined(__x86_64__)
+		WRITE_ONCE(vcpu->run->kvm_dirty_regs, KVM_SYNC_X86_REGS);
+		vcpu->run->s.regs.regs.rip += 3;
+#elif defined(__aarch64__)
+		vcpu_set_reg(vcpu, ARM64_CORE_REG(regs.pc),
+			     vcpu_get_reg(vcpu, ARM64_CORE_REG(regs.pc)) + 4);
+#endif
+
+	}
+	assert_sync_stage(vcpu, 3);
+#endif /* __x86_64__ || __aarch64__ */
+	rendezvous_with_boss();
+
+	/*
+	 * Stage 4.  Run to completion, waiting for mprotect(PROT_WRITE) to
+	 * make the memory writable again.
+	 */
+	do {
+		r = _vcpu_run(vcpu);
+	} while (r && errno == EFAULT);
+	TEST_ASSERT_EQ(r, 0);
+	assert_sync_stage(vcpu, 4);
+	rendezvous_with_boss();
+
+	return NULL;
+}
+
+static pthread_t *spawn_workers(struct kvm_vm *vm, struct kvm_vcpu **vcpus,
+				uint64_t start_gpa, uint64_t end_gpa)
+{
+	struct vcpu_info *info;
+	uint64_t gpa, nr_bytes;
+	pthread_t *threads;
+	int i;
+
+	threads = malloc(nr_vcpus * sizeof(*threads));
+	TEST_ASSERT(threads, "Failed to allocate vCPU threads");
+
+	info = malloc(nr_vcpus * sizeof(*info));
+	TEST_ASSERT(info, "Failed to allocate vCPU gpa ranges");
+
+	nr_bytes = ((end_gpa - start_gpa) / nr_vcpus) &
+			~((uint64_t)vm->page_size - 1);
+	TEST_ASSERT(nr_bytes, "C'mon, no way you have %d CPUs", nr_vcpus);
+
+	for (i = 0, gpa = start_gpa; i < nr_vcpus; i++, gpa += nr_bytes) {
+		info[i].vcpu = vcpus[i];
+		info[i].start_gpa = gpa;
+		info[i].end_gpa = gpa + nr_bytes;
+		pthread_create(&threads[i], NULL, vcpu_worker, &info[i]);
+	}
+	return threads;
+}
+
+static void rendezvous_with_vcpus(struct timespec *time, const char *name)
+{
+	int i, rendezvoused;
+
+	pr_info("Waiting for vCPUs to finish %s...\n", name);
+
+	rendezvoused = atomic_read(&rendezvous);
+	for (i = 0; abs(rendezvoused) != 1; i++) {
+		usleep(100);
+		if (!(i & 0x3f))
+			pr_info("\r%d vCPUs haven't rendezvoused...",
+				abs(rendezvoused) - 1);
+		rendezvoused = atomic_read(&rendezvous);
+	}
+
+	clock_gettime(CLOCK_MONOTONIC, time);
+
+	/* Release the vCPUs after getting the time of the previous action. */
+	pr_info("\rAll vCPUs finished %s, releasing...\n", name);
+	if (rendezvoused > 0)
+		atomic_set(&rendezvous, -nr_vcpus - 1);
+	else
+		atomic_set(&rendezvous, nr_vcpus + 1);
+}
+
+static void calc_default_nr_vcpus(void)
+{
+	cpu_set_t possible_mask;
+	int r;
+
+	r = sched_getaffinity(0, sizeof(possible_mask), &possible_mask);
+	TEST_ASSERT(!r, "sched_getaffinity failed, errno = %d (%s)",
+		    errno, strerror(errno));
+
+	nr_vcpus = CPU_COUNT(&possible_mask) * 3/4;
+	TEST_ASSERT(nr_vcpus > 0, "Uh, no CPUs?");
+}
+
+int main(int argc, char *argv[])
+{
+	/*
+	 * Skip the first 4gb and slot0.  slot0 maps <1gb and is used to back
+	 * the guest's code, stack, and page tables.  Because selftests creates
+	 * an IRQCHIP, a.k.a. a local APIC, KVM creates an internal memslot
+	 * just below the 4gb boundary.  This test could create memory at
+	 * 1gb-3gb,but it's simpler to skip straight to 4gb.
+	 */
+	const uint64_t start_gpa = SZ_4G;
+	const int first_slot = 1;
+
+	struct timespec time_start, time_run1, time_reset, time_run2, time_ro, time_rw;
+	uint64_t max_gpa, gpa, slot_size, max_mem, i;
+	int max_slots, slot, opt, fd;
+	bool hugepages = false;
+	struct kvm_vcpu **vcpus;
+	pthread_t *threads;
+	struct kvm_vm *vm;
+	void *mem;
+
+	/*
+	 * Default to 2gb so that maxing out systems with MAXPHADDR=46, which
+	 * are quite common for x86, requires changing only max_mem (KVM allows
+	 * 32k memslots, 32k * 2gb == ~64tb of guest memory).
+	 */
+	slot_size = SZ_2G;
+
+	max_slots = kvm_check_cap(KVM_CAP_NR_MEMSLOTS);
+	TEST_ASSERT(max_slots > first_slot, "KVM is broken");
+
+	/* All KVM MMUs should be able to survive a 128gb guest. */
+	max_mem = 128ull * SZ_1G;
+
+	calc_default_nr_vcpus();
+
+	while ((opt = getopt(argc, argv, "c:h:m:s:H")) != -1) {
+		switch (opt) {
+		case 'c':
+			nr_vcpus = atoi_positive("Number of vCPUs", optarg);
+			break;
+		case 'm':
+			max_mem = 1ull * atoi_positive("Memory size", optarg) * SZ_1G;
+			break;
+		case 's':
+			slot_size = 1ull * atoi_positive("Slot size", optarg) * SZ_1G;
+			break;
+		case 'H':
+			hugepages = true;
+			break;
+		case 'h':
+		default:
+			printf("usage: %s [-c nr_vcpus] [-m max_mem_in_gb] [-s slot_size_in_gb] [-H]\n", argv[0]);
+			exit(1);
+		}
+	}
+
+	vcpus = malloc(nr_vcpus * sizeof(*vcpus));
+	TEST_ASSERT(vcpus, "Failed to allocate vCPU array");
+
+	vm = __vm_create_with_vcpus(VM_SHAPE_DEFAULT, nr_vcpus,
+#ifdef __x86_64__
+				    max_mem / SZ_1G,
+#else
+				    max_mem / vm_guest_mode_params[VM_MODE_DEFAULT].page_size,
+#endif
+				    guest_code, vcpus);
+
+	max_gpa = vm->max_gfn << vm->page_shift;
+	TEST_ASSERT(max_gpa > (4 * slot_size), "MAXPHYADDR <4gb ");
+
+	fd = kvm_memfd_alloc(slot_size, hugepages);
+	mem = mmap(NULL, slot_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
+	TEST_ASSERT(mem != MAP_FAILED, "mmap() failed");
+
+	TEST_ASSERT(!madvise(mem, slot_size, MADV_NOHUGEPAGE), "madvise() failed");
+
+	/* Pre-fault the memory to avoid taking mmap_sem on guest page faults. */
+	for (i = 0; i < slot_size; i += vm->page_size)
+		((uint8_t *)mem)[i] = 0xaa;
+
+	gpa = 0;
+	for (slot = first_slot; slot < max_slots; slot++) {
+		gpa = start_gpa + ((slot - first_slot) * slot_size);
+		if (gpa + slot_size > max_gpa)
+			break;
+
+		if ((gpa - start_gpa) >= max_mem)
+			break;
+
+		vm_set_user_memory_region(vm, slot, 0, gpa, slot_size, mem);
+
+#ifdef __x86_64__
+		/* Identity map memory in the guest using 1gb pages. */
+		for (i = 0; i < slot_size; i += SZ_1G)
+			__virt_pg_map(vm, gpa + i, gpa + i, PG_LEVEL_1G);
+#else
+		for (i = 0; i < slot_size; i += vm->page_size)
+			virt_pg_map(vm, gpa + i, gpa + i);
+#endif
+	}
+
+	atomic_set(&rendezvous, nr_vcpus + 1);
+	threads = spawn_workers(vm, vcpus, start_gpa, gpa);
+
+	free(vcpus);
+	vcpus = NULL;
+
+	pr_info("Running with %lugb of guest memory and %u vCPUs\n",
+		(gpa - start_gpa) / SZ_1G, nr_vcpus);
+
+	rendezvous_with_vcpus(&time_start, "spawning");
+	rendezvous_with_vcpus(&time_run1, "run 1");
+	rendezvous_with_vcpus(&time_reset, "reset");
+	rendezvous_with_vcpus(&time_run2, "run 2");
+
+	mprotect(mem, slot_size, PROT_READ);
+	mprotect_ro_done = true;
+	sync_global_to_guest(vm, mprotect_ro_done);
+
+	rendezvous_with_vcpus(&time_ro, "mprotect RO");
+	mprotect(mem, slot_size, PROT_READ | PROT_WRITE);
+	rendezvous_with_vcpus(&time_rw, "mprotect RW");
+
+	time_rw    = timespec_sub(time_rw,     time_ro);
+	time_ro    = timespec_sub(time_ro,     time_run2);
+	time_run2  = timespec_sub(time_run2,   time_reset);
+	time_reset = timespec_sub(time_reset,  time_run1);
+	time_run1  = timespec_sub(time_run1,   time_start);
+
+	pr_info("run1 = %ld.%.9lds, reset = %ld.%.9lds, run2 = %ld.%.9lds, "
+		"ro = %ld.%.9lds, rw = %ld.%.9lds\n",
+		time_run1.tv_sec, time_run1.tv_nsec,
+		time_reset.tv_sec, time_reset.tv_nsec,
+		time_run2.tv_sec, time_run2.tv_nsec,
+		time_ro.tv_sec, time_ro.tv_nsec,
+		time_rw.tv_sec, time_rw.tv_nsec);
+
+	/*
+	 * Delete even numbered slots (arbitrary) and unmap the first half of
+	 * the backing (also arbitrary) to verify KVM correctly drops all
+	 * references to the removed regions.
+	 */
+	for (slot = (slot - 1) & ~1ull; slot >= first_slot; slot -= 2)
+		vm_set_user_memory_region(vm, slot, 0, 0, 0, NULL);
+
+	munmap(mem, slot_size / 2);
+
+	/* Sanity check that the vCPUs actually ran. */
+	for (i = 0; i < nr_vcpus; i++)
+		pthread_join(threads[i], NULL);
+
+	/*
+	 * Deliberately exit without deleting the remaining memslots or closing
+	 * kvm_fd to test cleanup via mmu_notifier.release.
+	 */
+}