KVM: selftests: Always run vCPU thread with blocked SIG_IPI

[mirror_ubuntu-jammy-kernel.git] / tools / testing / selftests / kvm / dirty_log_test.c

// SPDX-License-Identifier: GPL-2.0
/*
 * KVM dirty page logging test
 *
 * Copyright (C) 2018, Red Hat, Inc.
 */

#define _GNU_SOURCE /* for program_invocation_name */

#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 <asm/barrier.h>
#include <linux/atomic.h>

#include "kvm_util.h"
#include "test_util.h"
#include "guest_modes.h"
#include "processor.h"

#define VCPU_ID                         1

/* The memory slot index to track dirty pages */
#define TEST_MEM_SLOT_INDEX             1

/* Default guest test virtual memory offset */
#define DEFAULT_GUEST_TEST_MEM          0xc0000000

/* How many pages to dirty for each guest loop */
#define TEST_PAGES_PER_LOOP             1024

/* How many host loops to run (one KVM_GET_DIRTY_LOG for each loop) */
#define TEST_HOST_LOOP_N                32UL

/* Interval for each host loop (ms) */
#define TEST_HOST_LOOP_INTERVAL         10UL

/* Dirty bitmaps are always little endian, so we need to swap on big endian */
#if defined(__s390x__)
# define BITOP_LE_SWIZZLE       ((BITS_PER_LONG-1) & ~0x7)
# define test_bit_le(nr, addr) \
        test_bit((nr) ^ BITOP_LE_SWIZZLE, addr)
# define set_bit_le(nr, addr) \
        set_bit((nr) ^ BITOP_LE_SWIZZLE, addr)
# define clear_bit_le(nr, addr) \
        clear_bit((nr) ^ BITOP_LE_SWIZZLE, addr)
# define test_and_set_bit_le(nr, addr) \
        test_and_set_bit((nr) ^ BITOP_LE_SWIZZLE, addr)
# define test_and_clear_bit_le(nr, addr) \
        test_and_clear_bit((nr) ^ BITOP_LE_SWIZZLE, addr)
#else
# define test_bit_le            test_bit
# define set_bit_le             set_bit
# define clear_bit_le           clear_bit
# define test_and_set_bit_le    test_and_set_bit
# define test_and_clear_bit_le  test_and_clear_bit
#endif

#define TEST_DIRTY_RING_COUNT           65536

#define SIG_IPI SIGUSR1

/*
 * 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;
static uint64_t random_array[TEST_PAGES_PER_LOOP];
static uint64_t iteration;

/*
 * 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 a random pages within
 * the testing memory region.
 */
static void guest_code(void)
{
        uint64_t addr;
        int i;

        /*
         * On s390x, all pages of a 1M segment are initially marked as dirty
         * when a page of the segment is written to for the very first time.
         * To compensate this specialty in this test, we need to touch all
         * pages during the first iteration.
         */
        for (i = 0; i < guest_num_pages; i++) {
                addr = guest_test_virt_mem + i * guest_page_size;
                *(uint64_t *)addr = READ_ONCE(iteration);
        }

        while (true) {
                for (i = 0; i < TEST_PAGES_PER_LOOP; i++) {
                        addr = guest_test_virt_mem;
                        addr += (READ_ONCE(random_array[i]) % guest_num_pages)
                                * guest_page_size;
                        addr &= ~(host_page_size - 1);
                        *(uint64_t *)addr = READ_ONCE(iteration);
                }

                /* Tell the host that we need more random numbers */
                GUEST_SYNC(1);
        }
}

/* Host variables */
static bool host_quit;

/* Points to the test VM memory region on which we track dirty logs */
static void *host_test_mem;
static uint64_t host_num_pages;

/* For statistics only */
static uint64_t host_dirty_count;
static uint64_t host_clear_count;
static uint64_t host_track_next_count;

/* Whether dirty ring reset is requested, or finished */
static sem_t sem_vcpu_stop;
static sem_t sem_vcpu_cont;
/*
 * This is only set by main thread, and only cleared by vcpu thread.  It is
 * used to request vcpu thread to stop at the next GUEST_SYNC, since GUEST_SYNC
 * is the only place that we'll guarantee both "dirty bit" and "dirty data"
 * will match.  E.g., SIG_IPI won't guarantee that if the vcpu is interrupted
 * after setting dirty bit but before the data is written.
 */
static atomic_t vcpu_sync_stop_requested;
/*
 * This is updated by the vcpu thread to tell the host whether it's a
 * ring-full event.  It should only be read until a sem_wait() of
 * sem_vcpu_stop and before vcpu continues to run.
 */
static bool dirty_ring_vcpu_ring_full;
/*
 * This is only used for verifying the dirty pages.  Dirty ring has a very
 * tricky case when the ring just got full, kvm will do userspace exit due to
 * ring full.  When that happens, the very last PFN is set but actually the
 * data is not changed (the guest WRITE is not really applied yet), because
 * we found that the dirty ring is full, refused to continue the vcpu, and
 * recorded the dirty gfn with the old contents.
 *
 * For this specific case, it's safe to skip checking this pfn for this
 * bit, because it's a redundant bit, and when the write happens later the bit
 * will be set again.  We use this variable to always keep track of the latest
 * dirty gfn we've collected, so that if a mismatch of data found later in the
 * verifying process, we let it pass.
 */
static uint64_t dirty_ring_last_page;

enum log_mode_t {
        /* Only use KVM_GET_DIRTY_LOG for logging */
        LOG_MODE_DIRTY_LOG = 0,

        /* Use both KVM_[GET|CLEAR]_DIRTY_LOG for logging */
        LOG_MODE_CLEAR_LOG = 1,

        /* Use dirty ring for logging */
        LOG_MODE_DIRTY_RING = 2,

        LOG_MODE_NUM,

        /* Run all supported modes */
        LOG_MODE_ALL = LOG_MODE_NUM,
};

/* Mode of logging to test.  Default is to run all supported modes */
static enum log_mode_t host_log_mode_option = LOG_MODE_ALL;
/* Logging mode for current run */
static enum log_mode_t host_log_mode;
static pthread_t vcpu_thread;
static uint32_t test_dirty_ring_count = TEST_DIRTY_RING_COUNT;

static void vcpu_kick(void)
{
        pthread_kill(vcpu_thread, SIG_IPI);
}

/*
 * In our test we do signal tricks, let's use a better version of
 * sem_wait to avoid signal interrupts
 */
static void sem_wait_until(sem_t *sem)
{
        int ret;

        do
                ret = sem_wait(sem);
        while (ret == -1 && errno == EINTR);
}

static bool clear_log_supported(void)
{
        return kvm_check_cap(KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2);
}

static void clear_log_create_vm_done(struct kvm_vm *vm)
{
        struct kvm_enable_cap cap = {};
        u64 manual_caps;

        manual_caps = kvm_check_cap(KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2);
        TEST_ASSERT(manual_caps, "MANUAL_CAPS is zero!");
        manual_caps &= (KVM_DIRTY_LOG_MANUAL_PROTECT_ENABLE |
                        KVM_DIRTY_LOG_INITIALLY_SET);
        cap.cap = KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2;
        cap.args[0] = manual_caps;
        vm_enable_cap(vm, &cap);
}

static void dirty_log_collect_dirty_pages(struct kvm_vm *vm, int slot,
                                          void *bitmap, uint32_t num_pages)
{
        kvm_vm_get_dirty_log(vm, slot, bitmap);
}

static void clear_log_collect_dirty_pages(struct kvm_vm *vm, int slot,
                                          void *bitmap, uint32_t num_pages)
{
        kvm_vm_get_dirty_log(vm, slot, bitmap);
        kvm_vm_clear_dirty_log(vm, slot, bitmap, 0, num_pages);
}

/* Should only be called after a GUEST_SYNC */
static void vcpu_handle_sync_stop(void)
{
        if (atomic_read(&vcpu_sync_stop_requested)) {
                /* It means main thread is sleeping waiting */
                atomic_set(&vcpu_sync_stop_requested, false);
                sem_post(&sem_vcpu_stop);
                sem_wait_until(&sem_vcpu_cont);
        }
}

static void default_after_vcpu_run(struct kvm_vm *vm, int ret, int err)
{
        struct kvm_run *run = vcpu_state(vm, VCPU_ID);

        TEST_ASSERT(ret == 0 || (ret == -1 && err == EINTR),
                    "vcpu run failed: errno=%d", err);

        TEST_ASSERT(get_ucall(vm, VCPU_ID, NULL) == UCALL_SYNC,
                    "Invalid guest sync status: exit_reason=%s\n",
                    exit_reason_str(run->exit_reason));

        vcpu_handle_sync_stop();
}

static bool dirty_ring_supported(void)
{
        return kvm_check_cap(KVM_CAP_DIRTY_LOG_RING);
}

static void dirty_ring_create_vm_done(struct kvm_vm *vm)
{
        /*
         * Switch to dirty ring mode after VM creation but before any
         * of the vcpu creation.
         */
        vm_enable_dirty_ring(vm, test_dirty_ring_count *
                             sizeof(struct kvm_dirty_gfn));
}

static inline bool dirty_gfn_is_dirtied(struct kvm_dirty_gfn *gfn)
{
        return gfn->flags == KVM_DIRTY_GFN_F_DIRTY;
}

static inline void dirty_gfn_set_collected(struct kvm_dirty_gfn *gfn)
{
        gfn->flags = KVM_DIRTY_GFN_F_RESET;
}

static uint32_t dirty_ring_collect_one(struct kvm_dirty_gfn *dirty_gfns,
                                       int slot, void *bitmap,
                                       uint32_t num_pages, uint32_t *fetch_index)
{
        struct kvm_dirty_gfn *cur;
        uint32_t count = 0;

        while (true) {
                cur = &dirty_gfns[*fetch_index % test_dirty_ring_count];
                if (!dirty_gfn_is_dirtied(cur))
                        break;
                TEST_ASSERT(cur->slot == slot, "Slot number didn't match: "
                            "%u != %u", cur->slot, slot);
                TEST_ASSERT(cur->offset < num_pages, "Offset overflow: "
                            "0x%llx >= 0x%x", cur->offset, num_pages);
                //pr_info("fetch 0x%x page %llu\n", *fetch_index, cur->offset);
                set_bit_le(cur->offset, bitmap);
                dirty_ring_last_page = cur->offset;
                dirty_gfn_set_collected(cur);
                (*fetch_index)++;
                count++;
        }

        return count;
}

static void dirty_ring_wait_vcpu(void)
{
        /* This makes sure that hardware PML cache flushed */
        vcpu_kick();
        sem_wait_until(&sem_vcpu_stop);
}

static void dirty_ring_continue_vcpu(void)
{
        pr_info("Notifying vcpu to continue\n");
        sem_post(&sem_vcpu_cont);
}

static void dirty_ring_collect_dirty_pages(struct kvm_vm *vm, int slot,
                                           void *bitmap, uint32_t num_pages)
{
        /* We only have one vcpu */
        static uint32_t fetch_index = 0;
        uint32_t count = 0, cleared;
        bool continued_vcpu = false;

        dirty_ring_wait_vcpu();

        if (!dirty_ring_vcpu_ring_full) {
                /*
                 * This is not a ring-full event, it's safe to allow
                 * vcpu to continue
                 */
                dirty_ring_continue_vcpu();
                continued_vcpu = true;
        }

        /* Only have one vcpu */
        count = dirty_ring_collect_one(vcpu_map_dirty_ring(vm, VCPU_ID),
                                       slot, bitmap, num_pages, &fetch_index);

        cleared = kvm_vm_reset_dirty_ring(vm);

        /* Cleared pages should be the same as collected */
        TEST_ASSERT(cleared == count, "Reset dirty pages (%u) mismatch "
                    "with collected (%u)", cleared, count);

        if (!continued_vcpu) {
                TEST_ASSERT(dirty_ring_vcpu_ring_full,
                            "Didn't continue vcpu even without ring full");
                dirty_ring_continue_vcpu();
        }

        pr_info("Iteration %ld collected %u pages\n", iteration, count);
}

static void dirty_ring_after_vcpu_run(struct kvm_vm *vm, int ret, int err)
{
        struct kvm_run *run = vcpu_state(vm, VCPU_ID);

        /* A ucall-sync or ring-full event is allowed */
        if (get_ucall(vm, VCPU_ID, NULL) == UCALL_SYNC) {
                /* We should allow this to continue */
                ;
        } else if (run->exit_reason == KVM_EXIT_DIRTY_RING_FULL ||
                   (ret == -1 && err == EINTR)) {
                /* Update the flag first before pause */
                WRITE_ONCE(dirty_ring_vcpu_ring_full,
                           run->exit_reason == KVM_EXIT_DIRTY_RING_FULL);
                sem_post(&sem_vcpu_stop);
                pr_info("vcpu stops because %s...\n",
                        dirty_ring_vcpu_ring_full ?
                        "dirty ring is full" : "vcpu is kicked out");
                sem_wait_until(&sem_vcpu_cont);
                pr_info("vcpu continues now.\n");
        } else {
                TEST_ASSERT(false, "Invalid guest sync status: "
                            "exit_reason=%s\n",
                            exit_reason_str(run->exit_reason));
        }
}

static void dirty_ring_before_vcpu_join(void)
{
        /* Kick another round of vcpu just to make sure it will quit */
        sem_post(&sem_vcpu_cont);
}

struct log_mode {
        const char *name;
        /* Return true if this mode is supported, otherwise false */
        bool (*supported)(void);
        /* Hook when the vm creation is done (before vcpu creation) */
        void (*create_vm_done)(struct kvm_vm *vm);
        /* Hook to collect the dirty pages into the bitmap provided */
        void (*collect_dirty_pages) (struct kvm_vm *vm, int slot,
                                     void *bitmap, uint32_t num_pages);
        /* Hook to call when after each vcpu run */
        void (*after_vcpu_run)(struct kvm_vm *vm, int ret, int err);
        void (*before_vcpu_join) (void);
} log_modes[LOG_MODE_NUM] = {
        {
                .name = "dirty-log",
                .collect_dirty_pages = dirty_log_collect_dirty_pages,
                .after_vcpu_run = default_after_vcpu_run,
        },
        {
                .name = "clear-log",
                .supported = clear_log_supported,
                .create_vm_done = clear_log_create_vm_done,
                .collect_dirty_pages = clear_log_collect_dirty_pages,
                .after_vcpu_run = default_after_vcpu_run,
        },
        {
                .name = "dirty-ring",
                .supported = dirty_ring_supported,
                .create_vm_done = dirty_ring_create_vm_done,
                .collect_dirty_pages = dirty_ring_collect_dirty_pages,
                .before_vcpu_join = dirty_ring_before_vcpu_join,
                .after_vcpu_run = dirty_ring_after_vcpu_run,
        },
};

/*
 * We use this bitmap to track some pages that should have its dirty
 * bit set in the _next_ iteration.  For example, if we detected the
 * page value changed to current iteration but at the same time the
 * page bit is cleared in the latest bitmap, then the system must
 * report that write in the next get dirty log call.
 */
static unsigned long *host_bmap_track;

static void log_modes_dump(void)
{
        int i;

        printf("all");
        for (i = 0; i < LOG_MODE_NUM; i++)
                printf(", %s", log_modes[i].name);
        printf("\n");
}

static bool log_mode_supported(void)
{
        struct log_mode *mode = &log_modes[host_log_mode];

        if (mode->supported)
                return mode->supported();

        return true;
}

static void log_mode_create_vm_done(struct kvm_vm *vm)
{
        struct log_mode *mode = &log_modes[host_log_mode];

        if (mode->create_vm_done)
                mode->create_vm_done(vm);
}

static void log_mode_collect_dirty_pages(struct kvm_vm *vm, int slot,
                                         void *bitmap, uint32_t num_pages)
{
        struct log_mode *mode = &log_modes[host_log_mode];

        TEST_ASSERT(mode->collect_dirty_pages != NULL,
                    "collect_dirty_pages() is required for any log mode!");
        mode->collect_dirty_pages(vm, slot, bitmap, num_pages);
}

static void log_mode_after_vcpu_run(struct kvm_vm *vm, int ret, int err)
{
        struct log_mode *mode = &log_modes[host_log_mode];

        if (mode->after_vcpu_run)
                mode->after_vcpu_run(vm, ret, err);
}

static void log_mode_before_vcpu_join(void)
{
        struct log_mode *mode = &log_modes[host_log_mode];

        if (mode->before_vcpu_join)
                mode->before_vcpu_join();
}

static void generate_random_array(uint64_t *guest_array, uint64_t size)
{
        uint64_t i;

        for (i = 0; i < size; i++)
                guest_array[i] = random();
}

static void *vcpu_worker(void *data)
{
        int ret, vcpu_fd;
        struct kvm_vm *vm = data;
        uint64_t *guest_array;
        uint64_t pages_count = 0;
        struct kvm_signal_mask *sigmask = alloca(offsetof(struct kvm_signal_mask, sigset)
                                                 + sizeof(sigset_t));
        sigset_t *sigset = (sigset_t *) &sigmask->sigset;

        vcpu_fd = vcpu_get_fd(vm, VCPU_ID);

        /*
         * SIG_IPI is unblocked atomically while in KVM_RUN.  It causes the
         * ioctl to return with -EINTR, but it is still pending and we need
         * to accept it with the sigwait.
         */
        sigmask->len = 8;
        pthread_sigmask(0, NULL, sigset);
        sigdelset(sigset, SIG_IPI);
        vcpu_ioctl(vm, VCPU_ID, KVM_SET_SIGNAL_MASK, sigmask);

        sigemptyset(sigset);
        sigaddset(sigset, SIG_IPI);

        guest_array = addr_gva2hva(vm, (vm_vaddr_t)random_array);

        while (!READ_ONCE(host_quit)) {
                /* Clear any existing kick signals */
                generate_random_array(guest_array, TEST_PAGES_PER_LOOP);
                pages_count += TEST_PAGES_PER_LOOP;
                /* Let the guest dirty the random pages */
                ret = ioctl(vcpu_fd, KVM_RUN, NULL);
                if (ret == -1 && errno == EINTR) {
                        int sig = -1;
                        sigwait(sigset, &sig);
                        assert(sig == SIG_IPI);
                }
                log_mode_after_vcpu_run(vm, ret, errno);
        }

        pr_info("Dirtied %"PRIu64" pages\n", pages_count);

        return NULL;
}

static void vm_dirty_log_verify(enum vm_guest_mode mode, unsigned long *bmap)
{
        uint64_t step = vm_num_host_pages(mode, 1);
        uint64_t page;
        uint64_t *value_ptr;
        uint64_t min_iter = 0;

        for (page = 0; page < host_num_pages; page += step) {
                value_ptr = host_test_mem + page * host_page_size;

                /* If this is a special page that we were tracking... */
                if (test_and_clear_bit_le(page, host_bmap_track)) {
                        host_track_next_count++;
                        TEST_ASSERT(test_bit_le(page, bmap),
                                    "Page %"PRIu64" should have its dirty bit "
                                    "set in this iteration but it is missing",
                                    page);
                }

                if (test_and_clear_bit_le(page, bmap)) {
                        bool matched;

                        host_dirty_count++;

                        /*
                         * If the bit is set, the value written onto
                         * the corresponding page should be either the
                         * previous iteration number or the current one.
                         */
                        matched = (*value_ptr == iteration ||
                                   *value_ptr == iteration - 1);

                        if (host_log_mode == LOG_MODE_DIRTY_RING && !matched) {
                                if (*value_ptr == iteration - 2 && min_iter <= iteration - 2) {
                                        /*
                                         * Short answer: this case is special
                                         * only for dirty ring test where the
                                         * page is the last page before a kvm
                                         * dirty ring full in iteration N-2.
                                         *
                                         * Long answer: Assuming ring size R,
                                         * one possible condition is:
                                         *
                                         *      main thr       vcpu thr
                                         *      --------       --------
                                         *    iter=1
                                         *                   write 1 to page 0~(R-1)
                                         *                   full, vmexit
                                         *    collect 0~(R-1)
                                         *    kick vcpu
                                         *                   write 1 to (R-1)~(2R-2)
                                         *                   full, vmexit
                                         *    iter=2
                                         *    collect (R-1)~(2R-2)
                                         *    kick vcpu
                                         *                   write 1 to (2R-2)
                                         *                   (NOTE!!! "1" cached in cpu reg)
                                         *                   write 2 to (2R-1)~(3R-3)
                                         *                   full, vmexit
                                         *    iter=3
                                         *    collect (2R-2)~(3R-3)
                                         *    (here if we read value on page
                                         *     "2R-2" is 1, while iter=3!!!)
                                         *
                                         * This however can only happen once per iteration.
                                         */
                                        min_iter = iteration - 1;
                                        continue;
                                } else if (page == dirty_ring_last_page) {
                                        /*
                                         * Please refer to comments in
                                         * dirty_ring_last_page.
                                         */
                                        continue;
                                }
                        }

                        TEST_ASSERT(matched,
                                    "Set page %"PRIu64" value %"PRIu64
                                    " incorrect (iteration=%"PRIu64")",
                                    page, *value_ptr, iteration);
                } else {
                        host_clear_count++;
                        /*
                         * If cleared, the value written can be any
                         * value smaller or equals to the iteration
                         * number.  Note that the value can be exactly
                         * (iteration-1) if that write can happen
                         * like this:
                         *
                         * (1) increase loop count to "iteration-1"
                         * (2) write to page P happens (with value
                         *     "iteration-1")
                         * (3) get dirty log for "iteration-1"; we'll
                         *     see that page P bit is set (dirtied),
                         *     and not set the bit in host_bmap_track
                         * (4) increase loop count to "iteration"
                         *     (which is current iteration)
                         * (5) get dirty log for current iteration,
                         *     we'll see that page P is cleared, with
                         *     value "iteration-1".
                         */
                        TEST_ASSERT(*value_ptr <= iteration,
                                    "Clear page %"PRIu64" value %"PRIu64
                                    " incorrect (iteration=%"PRIu64")",
                                    page, *value_ptr, iteration);
                        if (*value_ptr == iteration) {
                                /*
                                 * This page is _just_ modified; it
                                 * should report its dirtyness in the
                                 * next run
                                 */
                                set_bit_le(page, host_bmap_track);
                        }
                }
        }
}

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;

        pr_info("Testing guest mode: %s\n", vm_guest_mode_string(mode));

        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
        log_mode_create_vm_done(vm);
        vm_vcpu_add_default(vm, vcpuid, guest_code);
        return vm;
}

#define DIRTY_MEM_BITS 30 /* 1G */
#define PAGE_SHIFT_4K  12

struct test_params {
        unsigned long iterations;
        unsigned long interval;
        uint64_t phys_offset;
};

static void run_test(enum vm_guest_mode mode, void *arg)
{
        struct test_params *p = arg;
        struct kvm_vm *vm;
        unsigned long *bmap;

        if (!log_mode_supported()) {
                print_skip("Log mode '%s' not supported",
                           log_modes[host_log_mode].name);
                return;
        }

        /*
         * 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 << (DIRTY_MEM_BITS - 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 << (DIRTY_MEM_BITS -
                                   vm_get_page_shift(vm))) + 3;
        guest_num_pages = vm_adjust_num_guest_pages(mode, guest_num_pages);

        host_page_size = getpagesize();
        host_num_pages = vm_num_host_pages(mode, guest_num_pages);

        if (!p->phys_offset) {
                guest_test_phys_mem = (vm_get_max_gfn(vm) -
                                       guest_num_pages) * guest_page_size;
                guest_test_phys_mem &= ~(host_page_size - 1);
        } else {
                guest_test_phys_mem = p->phys_offset;
        }

#ifdef __s390x__
        /* Align to 1M (segment size) */
        guest_test_phys_mem &= ~((1 << 20) - 1);
#endif

        pr_info("guest physical test memory offset: 0x%lx\n", guest_test_phys_mem);

        bmap = bitmap_alloc(host_num_pages);
        host_bmap_track = bitmap_alloc(host_num_pages);

        /* Add an extra memory slot for testing dirty logging */
        vm_userspace_mem_region_add(vm, VM_MEM_SRC_ANONYMOUS,
                                    guest_test_phys_mem,
                                    TEST_MEM_SLOT_INDEX,
                                    guest_num_pages,
                                    KVM_MEM_LOG_DIRTY_PAGES);

        /* Do mapping for the dirty track memory slot */
        virt_map(vm, guest_test_virt_mem, guest_test_phys_mem, guest_num_pages, 0);

        /* Cache the HVA pointer of the region */
        host_test_mem = addr_gpa2hva(vm, (vm_paddr_t)guest_test_phys_mem);

        ucall_init(vm, NULL);

        /* 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);

        /* Start the iterations */
        iteration = 1;
        sync_global_to_guest(vm, iteration);
        host_quit = false;
        host_dirty_count = 0;
        host_clear_count = 0;
        host_track_next_count = 0;

        pthread_create(&vcpu_thread, NULL, vcpu_worker, vm);

        while (iteration < p->iterations) {
                /* Give the vcpu thread some time to dirty some pages */
                usleep(p->interval * 1000);
                log_mode_collect_dirty_pages(vm, TEST_MEM_SLOT_INDEX,
                                             bmap, host_num_pages);

                /*
                 * See vcpu_sync_stop_requested definition for details on why
                 * we need to stop vcpu when verify data.
                 */
                atomic_set(&vcpu_sync_stop_requested, true);
                sem_wait_until(&sem_vcpu_stop);
                /*
                 * NOTE: for dirty ring, it's possible that we didn't stop at
                 * GUEST_SYNC but instead we stopped because ring is full;
                 * that's okay too because ring full means we're only missing
                 * the flush of the last page, and since we handle the last
                 * page specially verification will succeed anyway.
                 */
                assert(host_log_mode == LOG_MODE_DIRTY_RING ||
                       atomic_read(&vcpu_sync_stop_requested) == false);
                vm_dirty_log_verify(mode, bmap);
                sem_post(&sem_vcpu_cont);

                iteration++;
                sync_global_to_guest(vm, iteration);
        }

        /* Tell the vcpu thread to quit */
        host_quit = true;
        log_mode_before_vcpu_join();
        pthread_join(vcpu_thread, NULL);

        pr_info("Total bits checked: dirty (%"PRIu64"), clear (%"PRIu64"), "
                "track_next (%"PRIu64")\n", host_dirty_count, host_clear_count,
                host_track_next_count);

        free(bmap);
        free(host_bmap_track);
        ucall_uninit(vm);
        kvm_vm_free(vm);
}

static void help(char *name)
{
        puts("");
        printf("usage: %s [-h] [-i iterations] [-I interval] "
               "[-p offset] [-m mode]\n", name);
        puts("");
        printf(" -c: specify dirty ring size, in number of entries\n");
        printf("     (only useful for dirty-ring test; default: %"PRIu32")\n",
               TEST_DIRTY_RING_COUNT);
        printf(" -i: specify iteration counts (default: %"PRIu64")\n",
               TEST_HOST_LOOP_N);
        printf(" -I: specify interval in ms (default: %"PRIu64" ms)\n",
               TEST_HOST_LOOP_INTERVAL);
        printf(" -p: specify guest physical test memory offset\n"
               "     Warning: a low offset can conflict with the loaded test code.\n");
        printf(" -M: specify the host logging mode "
               "(default: run all log modes).  Supported modes: \n\t");
        log_modes_dump();
        guest_modes_help();
        puts("");
        exit(0);
}

int main(int argc, char *argv[])
{
        struct test_params p = {
                .iterations = TEST_HOST_LOOP_N,
                .interval = TEST_HOST_LOOP_INTERVAL,
        };
        int opt, i;
        sigset_t sigset;

        sem_init(&sem_vcpu_stop, 0, 0);
        sem_init(&sem_vcpu_cont, 0, 0);

        guest_modes_append_default();

        while ((opt = getopt(argc, argv, "c:hi:I:p:m:M:")) != -1) {
                switch (opt) {
                case 'c':
                        test_dirty_ring_count = strtol(optarg, NULL, 10);
                        break;
                case 'i':
                        p.iterations = strtol(optarg, NULL, 10);
                        break;
                case 'I':
                        p.interval = strtol(optarg, NULL, 10);
                        break;
                case 'p':
                        p.phys_offset = strtoull(optarg, NULL, 0);
                        break;
                case 'm':
                        guest_modes_cmdline(optarg);
                        break;
                case 'M':
                        if (!strcmp(optarg, "all")) {
                                host_log_mode_option = LOG_MODE_ALL;
                                break;
                        }
                        for (i = 0; i < LOG_MODE_NUM; i++) {
                                if (!strcmp(optarg, log_modes[i].name)) {
                                        pr_info("Setting log mode to: '%s'\n",
                                                optarg);
                                        host_log_mode_option = i;
                                        break;
                                }
                        }
                        if (i == LOG_MODE_NUM) {
                                printf("Log mode '%s' invalid. Please choose "
                                       "from: ", optarg);
                                log_modes_dump();
                                exit(1);
                        }
                        break;
                case 'h':
                default:
                        help(argv[0]);
                        break;
                }
        }

        TEST_ASSERT(p.iterations > 2, "Iterations must be greater than two");
        TEST_ASSERT(p.interval > 0, "Interval must be greater than zero");

        pr_info("Test iterations: %"PRIu64", interval: %"PRIu64" (ms)\n",
                p.iterations, p.interval);

        srandom(time(0));

        /* Ensure that vCPU threads start with SIG_IPI blocked.  */
        sigemptyset(&sigset);
        sigaddset(&sigset, SIG_IPI);
        pthread_sigmask(SIG_BLOCK, &sigset, NULL);

        if (host_log_mode_option == LOG_MODE_ALL) {
                /* Run each log mode */
                for (i = 0; i < LOG_MODE_NUM; i++) {
                        pr_info("Testing Log Mode '%s'\n", log_modes[i].name);
                        host_log_mode = i;
                        for_each_guest_mode(run_test, &p);
                }
        } else {
                host_log_mode = host_log_mode_option;
                for_each_guest_mode(run_test, &p);
        }

        return 0;
}