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

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

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

/* 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 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

/*
 * Ensure the vCPU is able to perform a reasonable number of writes in each
 * iteration to provide a lower bound on coverage.
 */
#define TEST_MIN_WRITES_PER_ITERATION   0x100

/* 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 iteration;
static uint64_t nr_writes;
static bool vcpu_stop;

/*
 * 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;

#ifdef __s390x__
        uint64_t 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;
                vcpu_arch_put_guest(*(uint64_t *)addr, READ_ONCE(iteration));
                nr_writes++;
        }
#endif

        while (true) {
                while (!READ_ONCE(vcpu_stop)) {
                        addr = guest_test_virt_mem;
                        addr += (guest_random_u64(&guest_rng) % guest_num_pages)
                                * guest_page_size;
                        addr = align_down(addr, host_page_size);

                        vcpu_arch_put_guest(*(uint64_t *)addr, READ_ONCE(iteration));
                        nr_writes++;
                }

                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;

/* Whether dirty ring reset is requested, or finished */
static sem_t sem_vcpu_stop;
static sem_t sem_vcpu_cont;

/*
 * 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 = -1ULL;

/*
 * In addition to the above, it is possible (especially if this
 * test is run nested) for the above scenario to repeat multiple times:
 *
 * The following can happen:
 *
 * - L1 vCPU:        Memory write is logged to PML but not committed.
 *
 * - L1 test thread: Ignores the write because its last dirty ring entry
 *                   Resets the dirty ring which:
 *                     - Resets the A/D bits in EPT
 *                     - Issues tlb flush (invept), which is intercepted by L0
 *
 * - L0: frees the whole nested ept mmu root as the response to invept,
 *       and thus ensures that when memory write is retried, it will fault again
 *
 * - L1 vCPU:        Same memory write is logged to the PML but not committed again.
 *
 * - L1 test thread: Ignores the write because its last dirty ring entry (again)
 *                   Resets the dirty ring which:
 *                     - Resets the A/D bits in EPT (again)
 *                     - Issues tlb flush (again) which is intercepted by L0
 *
 * ...
 *
 * N times
 *
 * - L1 vCPU:        Memory write is logged in the PML and then committed.
 *                   Lots of other memory writes are logged and committed.
 * ...
 *
 * - L1 test thread: Sees the memory write along with other memory writes
 *                   in the dirty ring, and since the write is usually not
 *                   the last entry in the dirty-ring and has a very outdated
 *                   iteration, the test fails.
 *
 *
 * Note that this is only possible when the write was the last log entry
 * write during iteration N-1, thus remember last iteration last log entry
 * and also don't fail when it is reported in the next iteration, together with
 * an outdated iteration count.
 */
static uint64_t dirty_ring_prev_iteration_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 bool clear_log_supported(void)
{
        return kvm_has_cap(KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2);
}

static void clear_log_create_vm_done(struct kvm_vm *vm)
{
        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);
        vm_enable_cap(vm, KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2, manual_caps);
}

static void dirty_log_collect_dirty_pages(struct kvm_vcpu *vcpu, int slot,
                                          void *bitmap, uint32_t num_pages,
                                          uint32_t *unused)
{
        kvm_vm_get_dirty_log(vcpu->vm, slot, bitmap);
}

static void clear_log_collect_dirty_pages(struct kvm_vcpu *vcpu, int slot,
                                          void *bitmap, uint32_t num_pages,
                                          uint32_t *unused)
{
        kvm_vm_get_dirty_log(vcpu->vm, slot, bitmap);
        kvm_vm_clear_dirty_log(vcpu->vm, slot, bitmap, 0, num_pages);
}

/* Should only be called after a GUEST_SYNC */
static void vcpu_handle_sync_stop(void)
{
        if (READ_ONCE(vcpu_stop)) {
                sem_post(&sem_vcpu_stop);
                sem_wait(&sem_vcpu_cont);
        }
}

static void default_after_vcpu_run(struct kvm_vcpu *vcpu)
{
        struct kvm_run *run = vcpu->run;

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

        vcpu_handle_sync_stop();
}

static bool dirty_ring_supported(void)
{
        return (kvm_has_cap(KVM_CAP_DIRTY_LOG_RING) ||
                kvm_has_cap(KVM_CAP_DIRTY_LOG_RING_ACQ_REL));
}

static void dirty_ring_create_vm_done(struct kvm_vm *vm)
{
        uint64_t pages;
        uint32_t limit;

        /*
         * We rely on vcpu exit due to full dirty ring state. Adjust
         * the ring buffer size to ensure we're able to reach the
         * full dirty ring state.
         */
        pages = (1ul << (DIRTY_MEM_BITS - vm->page_shift)) + 3;
        pages = vm_adjust_num_guest_pages(vm->mode, pages);
        if (vm->page_size < getpagesize())
                pages = vm_num_host_pages(vm->mode, pages);

        limit = 1 << (31 - __builtin_clz(pages));
        test_dirty_ring_count = 1 << (31 - __builtin_clz(test_dirty_ring_count));
        test_dirty_ring_count = min(limit, test_dirty_ring_count);
        pr_info("dirty ring count: 0x%x\n", test_dirty_ring_count);

        /*
         * 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 smp_load_acquire(&gfn->flags) == KVM_DIRTY_GFN_F_DIRTY;
}

static inline void dirty_gfn_set_collected(struct kvm_dirty_gfn *gfn)
{
        smp_store_release(&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);
                __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_collect_dirty_pages(struct kvm_vcpu *vcpu, int slot,
                                           void *bitmap, uint32_t num_pages,
                                           uint32_t *ring_buf_idx)
{
        uint32_t count, cleared;

        /* Only have one vcpu */
        count = dirty_ring_collect_one(vcpu_map_dirty_ring(vcpu),
                                       slot, bitmap, num_pages,
                                       ring_buf_idx);

        cleared = kvm_vm_reset_dirty_ring(vcpu->vm);

        /*
         * Cleared pages should be the same as collected, as KVM is supposed to
         * clear only the entries that have been harvested.
         */
        TEST_ASSERT(cleared == count, "Reset dirty pages (%u) mismatch "
                    "with collected (%u)", cleared, count);
}

static void dirty_ring_after_vcpu_run(struct kvm_vcpu *vcpu)
{
        struct kvm_run *run = vcpu->run;

        /* A ucall-sync or ring-full event is allowed */
        if (get_ucall(vcpu, NULL) == UCALL_SYNC) {
                vcpu_handle_sync_stop();
        } else if (run->exit_reason == KVM_EXIT_DIRTY_RING_FULL) {
                WRITE_ONCE(dirty_ring_vcpu_ring_full, true);
                vcpu_handle_sync_stop();
        } else {
                TEST_ASSERT(false, "Invalid guest sync status: "
                            "exit_reason=%s",
                            exit_reason_str(run->exit_reason));
        }
}

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_vcpu *vcpu, int slot,
                                     void *bitmap, uint32_t num_pages,
                                     uint32_t *ring_buf_idx);
        /* Hook to call when after each vcpu run */
        void (*after_vcpu_run)(struct kvm_vcpu *vcpu);
} 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,
                .after_vcpu_run = dirty_ring_after_vcpu_run,
        },
};

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_vcpu *vcpu, int slot,
                                         void *bitmap, uint32_t num_pages,
                                         uint32_t *ring_buf_idx)
{
        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(vcpu, slot, bitmap, num_pages, ring_buf_idx);
}

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

        if (mode->after_vcpu_run)
                mode->after_vcpu_run(vcpu);
}

static void *vcpu_worker(void *data)
{
        struct kvm_vcpu *vcpu = data;

        sem_wait(&sem_vcpu_cont);

        while (!READ_ONCE(host_quit)) {
                /* Let the guest dirty the random pages */
                vcpu_run(vcpu);
                log_mode_after_vcpu_run(vcpu);
        }

        return NULL;
}

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

        for (page = 0; page < host_num_pages; page += step) {
                uint64_t val = *(uint64_t *)(host_test_mem + page * host_page_size);
                bool bmap0_dirty = __test_and_clear_bit_le(page, bmap[0]);

                /*
                 * Ensure both bitmaps are cleared, as a page can be written
                 * multiple times per iteration, i.e. can show up in both
                 * bitmaps, and the dirty ring is additive, i.e. doesn't purge
                 * bitmap entries from previous collections.
                 */
                if (__test_and_clear_bit_le(page, bmap[1]) || bmap0_dirty) {
                        nr_dirty_pages++;

                        /*
                         * If the page is dirty, the value written to memory
                         * should be the current iteration number.
                         */
                        if (val == iteration)
                                continue;

                        if (host_log_mode == LOG_MODE_DIRTY_RING) {
                                /*
                                 * The last page in the ring from previous
                                 * iteration can be written with the value
                                 * from the previous iteration, as the value to
                                 * be written may be cached in a CPU register.
                                 */
                                if (page == dirty_ring_prev_iteration_last_page &&
                                    val == iteration - 1)
                                        continue;

                                /*
                                 * Any value from a previous iteration is legal
                                 * for the last entry, as the write may not yet
                                 * have retired, i.e. the page may hold whatever
                                 * it had before this iteration started.
                                 */
                                if (page == dirty_ring_last_page &&
                                    val < iteration)
                                        continue;
                        } else if (!val && iteration == 1 && bmap0_dirty) {
                                /*
                                 * When testing get+clear, the dirty bitmap
                                 * starts with all bits set, and so the first
                                 * iteration can observe a "dirty" page that
                                 * was never written, but only in the first
                                 * bitmap (collecting the bitmap also clears
                                 * all dirty pages).
                                 */
                                continue;
                        }

                        TEST_FAIL("Dirty page %lu value (%lu) != iteration (%lu) "
                                  "(last = %lu, prev_last = %lu)",
                                  page, val, iteration, dirty_ring_last_page,
                                  dirty_ring_prev_iteration_last_page);
                } else {
                        nr_clean_pages++;
                        /*
                         * If cleared, the value written can be any
                         * value smaller than the iteration number.
                         */
                        TEST_ASSERT(val < iteration,
                                    "Clear page %lu value (%lu) >= iteration (%lu) "
                                    "(last = %lu, prev_last = %lu)",
                                    page, val, iteration, dirty_ring_last_page,
                                    dirty_ring_prev_iteration_last_page);
                }
        }

        pr_info("Iteration %2ld: dirty: %-6lu clean: %-6lu writes: %-6lu\n",
                iteration, nr_dirty_pages, nr_clean_pages, nr_writes);

        host_dirty_count += nr_dirty_pages;
        host_clear_count += nr_clean_pages;
}

static struct kvm_vm *create_vm(enum vm_guest_mode mode, struct kvm_vcpu **vcpu,
                                uint64_t extra_mem_pages, void *guest_code)
{
        struct kvm_vm *vm;

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

        vm = __vm_create(VM_SHAPE(mode), 1, extra_mem_pages);

        log_mode_create_vm_done(vm);
        *vcpu = vm_vcpu_add(vm, 0, guest_code);
        kvm_arch_vm_finalize_vcpus(vm);
        return vm;
}

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_vcpu *vcpu;
        struct kvm_vm *vm;
        unsigned long *bmap[2];
        uint32_t ring_buf_idx = 0;
        int sem_val;

        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,
                       2ul << (DIRTY_MEM_BITS - PAGE_SHIFT_4K), guest_code);

        guest_page_size = vm->page_size;
        /*
         * 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->page_shift)) + 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->max_gfn - guest_num_pages) *
                                      guest_page_size;
                guest_test_phys_mem = align_down(guest_test_phys_mem, host_page_size);
        } else {
                guest_test_phys_mem = p->phys_offset;
        }

#ifdef __s390x__
        /* Align to 1M (segment size) */
        guest_test_phys_mem = align_down(guest_test_phys_mem, 1 << 20);

        /*
         * The workaround in guest_code() to write all pages prior to the first
         * iteration isn't compatible with the dirty ring, as the dirty ring
         * support relies on the vCPU to actually stop when vcpu_stop is set so
         * that the vCPU doesn't hang waiting for the dirty ring to be emptied.
         */
        TEST_ASSERT(host_log_mode != LOG_MODE_DIRTY_RING,
                    "Test needs to be updated to support s390 dirty ring");
#endif

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

        bmap[0] = bitmap_zalloc(host_num_pages);
        bmap[1] = bitmap_zalloc(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);

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

        /* 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);

        host_dirty_count = 0;
        host_clear_count = 0;
        WRITE_ONCE(host_quit, false);

        /*
         * Ensure the previous iteration didn't leave a dangling semaphore, i.e.
         * that the main task and vCPU worker were synchronized and completed
         * verification of all iterations.
         */
        sem_getvalue(&sem_vcpu_stop, &sem_val);
        TEST_ASSERT_EQ(sem_val, 0);
        sem_getvalue(&sem_vcpu_cont, &sem_val);
        TEST_ASSERT_EQ(sem_val, 0);

        TEST_ASSERT_EQ(vcpu_stop, false);

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

        for (iteration = 1; iteration <= p->iterations; iteration++) {
                unsigned long i;

                sync_global_to_guest(vm, iteration);

                WRITE_ONCE(nr_writes, 0);
                sync_global_to_guest(vm, nr_writes);

                dirty_ring_prev_iteration_last_page = dirty_ring_last_page;
                WRITE_ONCE(dirty_ring_vcpu_ring_full, false);

                sem_post(&sem_vcpu_cont);

                /*
                 * Let the vCPU run beyond the configured interval until it has
                 * performed the minimum number of writes.  This verifies the
                 * guest is making forward progress, e.g. isn't stuck because
                 * of a KVM bug, and puts a firm floor on test coverage.
                 */
                for (i = 0; i < p->interval || nr_writes < TEST_MIN_WRITES_PER_ITERATION; i++) {
                        /*
                         * Sleep in 1ms chunks to keep the interval math simple
                         * and so that the test doesn't run too far beyond the
                         * specified interval.
                         */
                        usleep(1000);

                        sync_global_from_guest(vm, nr_writes);

                        /*
                         * Reap dirty pages while the guest is running so that
                         * dirty ring full events are resolved, i.e. so that a
                         * larger interval doesn't always end up with a vCPU
                         * that's effectively blocked.  Collecting while the
                         * guest is running also verifies KVM doesn't lose any
                         * state.
                         *
                         * For bitmap modes, KVM overwrites the entire bitmap,
                         * i.e. collecting the bitmaps is destructive.  Collect
                         * the bitmap only on the first pass, otherwise this
                         * test would lose track of dirty pages.
                         */
                        if (i && host_log_mode != LOG_MODE_DIRTY_RING)
                                continue;

                        /*
                         * For the dirty ring, empty the ring on subsequent
                         * passes only if the ring was filled at least once,
                         * to verify KVM's handling of a full ring (emptying
                         * the ring on every pass would make it unlikely the
                         * vCPU would ever fill the fing).
                         */
                        if (i && !READ_ONCE(dirty_ring_vcpu_ring_full))
                                continue;

                        log_mode_collect_dirty_pages(vcpu, TEST_MEM_SLOT_INDEX,
                                                     bmap[0], host_num_pages,
                                                     &ring_buf_idx);
                }

                /*
                 * Stop the vCPU prior to collecting and verifying the dirty
                 * log.  If the vCPU is allowed to run during collection, then
                 * pages that are written during this iteration may be missed,
                 * i.e. collected in the next iteration.  And if the vCPU is
                 * writing memory during verification, pages that this thread
                 * sees as clean may be written with this iteration's value.
                 */
                WRITE_ONCE(vcpu_stop, true);
                sync_global_to_guest(vm, vcpu_stop);
                sem_wait(&sem_vcpu_stop);

                /*
                 * Clear vcpu_stop after the vCPU thread has acknowledge the
                 * stop request and is waiting, i.e. is definitely not running!
                 */
                WRITE_ONCE(vcpu_stop, false);
                sync_global_to_guest(vm, vcpu_stop);

                /*
                 * Sync the number of writes performed before verification, the
                 * info will be printed along with the dirty/clean page counts.
                 */
                sync_global_from_guest(vm, nr_writes);

                /*
                 * 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.
                 */
                log_mode_collect_dirty_pages(vcpu, TEST_MEM_SLOT_INDEX,
                                             bmap[1], host_num_pages,
                                             &ring_buf_idx);
                vm_dirty_log_verify(mode, bmap);
        }

        WRITE_ONCE(host_quit, true);
        sem_post(&sem_vcpu_cont);

        pthread_join(vcpu_thread, NULL);

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

        free(bmap[0]);
        free(bmap[1]);
        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: hint to 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;

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

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

        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;
}