[PATCH v2 1/8] KVM: selftests: Create a demand paging test

Ben Gardon
2019-12-16T21:36:41Z

While userfaultfd, KVM's demand paging implementation, is not specific
to KVM, having a benchmark for its performance will be useful for
guiding performance improvements to KVM. As a first step towards creating
a userfaultfd demand paging test, create a simple memory access test,
based on dirty_log_test.

Signed-off-by: Ben Gardon <bgardon@google.com>
---
tools/testing/selftests/kvm/.gitignore | 1 +
tools/testing/selftests/kvm/Makefile | 1 +
.../selftests/kvm/demand_paging_test.c | 268 ++++++++++++++++++
3 files changed, 270 insertions(+)
create mode 100644 tools/testing/selftests/kvm/demand_paging_test.c

diff --git a/tools/testing/selftests/kvm/.gitignore b/tools/testing/selftests/kvm/.gitignore
index 30072c3f52fbe..9619d96e15c41 100644
--- a/tools/testing/selftests/kvm/.gitignore
+++ b/tools/testing/selftests/kvm/.gitignore
@@ -17,3 +17,4 @@
/clear_dirty_log_test
/dirty_log_test
/kvm_create_max_vcpus
+/demand_paging_test
diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
index 3138a916574a9..8c412cdd527e6 100644
--- a/tools/testing/selftests/kvm/Makefile
+++ b/tools/testing/selftests/kvm/Makefile
@@ -28,6 +28,7 @@ TEST_GEN_PROGS_x86_64 += x86_64/vmx_tsc_adjust_test
TEST_GEN_PROGS_x86_64 += x86_64/xss_msr_test
TEST_GEN_PROGS_x86_64 += clear_dirty_log_test
TEST_GEN_PROGS_x86_64 += dirty_log_test
+TEST_GEN_PROGS_x86_64 += demand_paging_test
TEST_GEN_PROGS_x86_64 += kvm_create_max_vcpus

TEST_GEN_PROGS_aarch64 += clear_dirty_log_test
diff --git a/tools/testing/selftests/kvm/demand_paging_test.c b/tools/testing/selftests/kvm/demand_paging_test.c
new file mode 100644
index 0000000000000..36e12db5da56b
--- /dev/null
+++ b/tools/testing/selftests/kvm/demand_paging_test.c
@@ -0,0 +1,268 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * KVM demand paging test
+ * Adapted from dirty_log_test.c
+ *
+ * Copyright (C) 2018, Red Hat, Inc.
+ * Copyright (C) 2019, Google, Inc.
+ */
+
+#define _GNU_SOURCE /* for program_invocation_name */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <time.h>
+#include <pthread.h>
+#include <linux/bitmap.h>
+#include <linux/bitops.h>
+
+#include "test_util.h"
+#include "kvm_util.h"
+#include "processor.h"
+
+#define VCPU_ID 1
+
+/* The memory slot index demand page */
+#define TEST_MEM_SLOT_INDEX 1
+
+/* Default guest test virtual memory offset */
+#define DEFAULT_GUEST_TEST_MEM 0xc0000000
+
+/*
+ * Guest/Host shared variables. Ensure addr_gva2hva() and/or
+ * sync_global_to/from_guest() are used when accessing from
+ * the host. READ/WRITE_ONCE() should also be used with anything
+ * that may change.
+ */
+static uint64_t host_page_size;
+static uint64_t guest_page_size;
+static uint64_t guest_num_pages;
+
+/*
+ * Guest physical memory offset of the testing memory slot.
+ * This will be set to the topmost valid physical address minus
+ * the test memory size.
+ */
+static uint64_t guest_test_phys_mem;
+
+/*
+ * Guest virtual memory offset of the testing memory slot.
+ * Must not conflict with identity mapped test code.
+ */
+static uint64_t guest_test_virt_mem = DEFAULT_GUEST_TEST_MEM;
+
+/*
+ * Continuously write to the first 8 bytes of each page in the demand paging
+ * memory region.
+ */
+static void guest_code(void)
+{
+ int i;
+
+ for (i = 0; i < guest_num_pages; i++) {
+ uint64_t addr = guest_test_virt_mem;
+
+ addr += i * guest_page_size;
+ addr &= ~(host_page_size - 1);
+ *(uint64_t *)addr = 0x0123456789ABCDEF;
+ }
+
+ GUEST_SYNC(1);
+}
+
+/* Points to the test VM memory region on which we are doing demand paging */
+static void *host_test_mem;
+static uint64_t host_num_pages;
+
+static void *vcpu_worker(void *data)
+{
+ int ret;
+ struct kvm_vm *vm = data;
+ struct kvm_run *run;
+
+ run = vcpu_state(vm, VCPU_ID);
+
+ /* Let the guest access its memory */
+ ret = _vcpu_run(vm, VCPU_ID);
+ TEST_ASSERT(ret == 0, "vcpu_run failed: %d\n", ret);
+ if (get_ucall(vm, VCPU_ID, NULL) != UCALL_SYNC) {
+ TEST_ASSERT(false,
+ "Invalid guest sync status: exit_reason=%s\n",
+ exit_reason_str(run->exit_reason));
+ }
+
+ return NULL;
+}
+
+static struct kvm_vm *create_vm(enum vm_guest_mode mode, uint32_t vcpuid,
+ uint64_t extra_mem_pages, void *guest_code)
+{
+ struct kvm_vm *vm;
+ uint64_t extra_pg_pages = extra_mem_pages / 512 * 2;
+
+ vm = _vm_create(mode, DEFAULT_GUEST_PHY_PAGES + extra_pg_pages, O_RDWR);
+ kvm_vm_elf_load(vm, program_invocation_name, 0, 0);
+#ifdef __x86_64__
+ vm_create_irqchip(vm);
+#endif
+ vm_vcpu_add_default(vm, vcpuid, guest_code);
+ return vm;
+}
+
+#define GUEST_MEM_SHIFT 30 /* 1G */
+#define PAGE_SHIFT_4K 12
+
+static void run_test(enum vm_guest_mode mode)
+{
+ pthread_t vcpu_thread;
+ struct kvm_vm *vm;
+
+ /*
+ * We reserve page table for 2 times of extra dirty mem which
+ * will definitely cover the original (1G+) test range. Here
+ * we do the calculation with 4K page size which is the
+ * smallest so the page number will be enough for all archs
+ * (e.g., 64K page size guest will need even less memory for
+ * page tables).
+ */
+ vm = create_vm(mode, VCPU_ID,
+ 2ul << (GUEST_MEM_SHIFT - PAGE_SHIFT_4K),
+ guest_code);
+
+ guest_page_size = vm_get_page_size(vm);
+ /*
+ * A little more than 1G of guest page sized pages. Cover the
+ * case where the size is not aligned to 64 pages.
+ */
+ guest_num_pages = (1ul << (GUEST_MEM_SHIFT -
+ vm_get_page_shift(vm))) + 16;
+#ifdef __s390x__
+ /* Round up to multiple of 1M (segment size) */
+ guest_num_pages = (guest_num_pages + 0xff) & ~0xffUL;
+#endif
+
+ host_page_size = getpagesize();
+ host_num_pages = (guest_num_pages * guest_page_size) / host_page_size +
+ !!((guest_num_pages * guest_page_size) %
+ host_page_size);
+
+ guest_test_phys_mem = (vm_get_max_gfn(vm) - guest_num_pages) *
+ guest_page_size;
+ guest_test_phys_mem &= ~(host_page_size - 1);
+
+#ifdef __s390x__
+ /* Align to 1M (segment size) */
+ guest_test_phys_mem &= ~((1 << 20) - 1);
+#endif
+
+ DEBUG("guest physical test memory offset: 0x%lx\n",
+ guest_test_phys_mem);
+
+
+ /* Add an extra memory slot for testing demand paging */
+ vm_userspace_mem_region_add(vm, VM_MEM_SRC_ANONYMOUS,
+ guest_test_phys_mem,
+ TEST_MEM_SLOT_INDEX,
+ guest_num_pages, 0);
+
+ /* Do mapping for the demand paging memory slot */
+ virt_map(vm, guest_test_virt_mem, guest_test_phys_mem,
+ guest_num_pages * guest_page_size, 0);
+
+ /* Cache the HVA pointer of the region */
+ host_test_mem = addr_gpa2hva(vm, (vm_paddr_t)guest_test_phys_mem);
+
+#ifdef __x86_64__
+ vcpu_set_cpuid(vm, VCPU_ID, kvm_get_supported_cpuid());
+#endif
+
+ /* Export the shared variables to the guest */
+ sync_global_to_guest(vm, host_page_size);
+ sync_global_to_guest(vm, guest_page_size);
+ sync_global_to_guest(vm, guest_test_virt_mem);
+ sync_global_to_guest(vm, guest_num_pages);
+
+ pthread_create(&vcpu_thread, NULL, vcpu_worker, vm);
+
+ /* Wait for the vcpu thread to quit */
+ pthread_join(vcpu_thread, NULL);
+
+ ucall_uninit(vm);
+ kvm_vm_free(vm);
+}
+
+struct vm_guest_mode_params {
+ bool supported;
+ bool enabled;
+};
+struct vm_guest_mode_params vm_guest_mode_params[NUM_VM_MODES];
+
+#define vm_guest_mode_params_init(mode, supported, enabled) \
+({ \
+ vm_guest_mode_params[mode] = \
+ (struct vm_guest_mode_params){ supported, enabled }; \
+})
+
+static void help(char *name)
+{
+ int i;
+
+ puts("");
+ printf("usage: %s [-h] [-m mode]\n", name);
+ printf(" -m: specify the guest mode ID to test\n"
+ " (default: test all supported modes)\n"
+ " This option may be used multiple times.\n"
+ " Guest mode IDs:\n");
+ for (i = 0; i < NUM_VM_MODES; ++i) {
+ printf(" %d: %s%s\n", i, vm_guest_mode_string(i),
+ vm_guest_mode_params[i].supported ? " (supported)" : "");
+ }
+ puts("");
+ exit(0);
+}
+
+int main(int argc, char *argv[])
+{
+ bool mode_selected = false;
+ unsigned int mode;
+ int opt, i;
+
+#ifdef __x86_64__
+ vm_guest_mode_params_init(VM_MODE_PXXV48_4K, true, true);
+#endif
+#ifdef __s390x__
+ vm_guest_mode_params_init(VM_MODE_P40V48_4K, true, true);
+#endif
+
+ while ((opt = getopt(argc, argv, "hm:")) != -1) {
+ switch (opt) {
+ case 'm':
+ if (!mode_selected) {
+ for (i = 0; i < NUM_VM_MODES; ++i)
+ vm_guest_mode_params[i].enabled = false;
+ mode_selected = true;
+ }
+ mode = strtoul(optarg, NULL, 10);
+ TEST_ASSERT(mode < NUM_VM_MODES,
+ "Guest mode ID %d too big", mode);
+ vm_guest_mode_params[mode].enabled = true;
+ break;
+ case 'h':
+ default:
+ help(argv[0]);
+ break;
+ }
+ }
+
+ for (i = 0; i < NUM_VM_MODES; ++i) {
+ if (!vm_guest_mode_params[i].enabled)
+ continue;
+ TEST_ASSERT(vm_guest_mode_params[i].supported,
+ "Guest mode ID %d (%s) not supported.",
+ i, vm_guest_mode_string(i));
+ run_test(i);
+ }
+
+ return 0;
+}
--
2.24.1.735.g03f4e72817-goog