/*
 * This file and its contents are supplied under the terms of the
 * Common Development and Distribution License ("CDDL"), version 1.0.
 * You may only use this file in accordance with the terms of version
 * 1.0 of the CDDL.
 *
 * A full copy of the text of the CDDL should have accompanied this
 * source.  A copy of the CDDL is also available via the Internet at
 * http://www.illumos.org/license/CDDL.
 */

/*
 * Copyright 2022 Oxide Computer Company
 */

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <strings.h>
#include <libgen.h>
#include <assert.h>
#include <errno.h>

#include <sys/types.h>
#include <sys/sysmacros.h>
#include <sys/debug.h>
#include <sys/vmm.h>
#include <sys/vmm_dev.h>
#include <vmmapi.h>

#include "in_guest.h"
#include "test_defs.h"

typedef struct reading {
        hrtime_t        when;
        uint32_t        value;
} reading_t;

static bool
check_reading(reading_t before, reading_t after, uint_t divisor,
    uint_t tick_margin, uint_t ppm_margin)
{
        hrtime_t time_delta = after.when - before.when;
        uint32_t tick_delta;

        /*
         * The ticks margin should shrink proportionally to how coarsely the
         * timer clock is being divided.
         */
        tick_margin /= divisor;

        /* timer is counting down, so act appropriately */
        if (after.value > before.value) {
                /* handle rollover */
                tick_delta = (UINT32_MAX - after.value) + before.value;
        } else {
                tick_delta = before.value - after.value;
        }

        /* is the number of ticks OK? */
        if (tick_delta < LAPIC_TARGET_TICKS) {
                test_fail_msg("inadequate passage of ticks %u < %u\n",
                    tick_delta, LAPIC_TARGET_TICKS);
        } else if ((tick_delta - LAPIC_TARGET_TICKS) > tick_margin) {
                (void) printf("%u ticks outside margin %u\n", tick_delta,
                    LAPIC_TARGET_TICKS + tick_margin);
                return (false);
        }

        hrtime_t time_target = (tick_delta * NANOSEC * divisor) / LAPIC_FREQ;

        hrtime_t offset;
        if (time_delta < time_target) {
                offset = time_target - time_delta;
        } else {
                offset = time_delta - time_target;
        }
        uint64_t ppm = (offset * 1000000) / time_target;
        (void) printf("params: tick_margin=%u ppm_margin=%lu divisor=%u\n",
            tick_margin, ppm_margin, divisor);
        (void) printf("%u ticks in %lu ns (error %lu ppm)\n",
            tick_delta, time_delta, ppm);
        if (ppm > ppm_margin) {
                (void) printf("UNACCEPTABLE!\n");
                return (false);
        }
        return (true);
}


static void
test_for_divisor(struct vcpu *vcpu, uint_t divisor, struct vm_entry *ventry,
    struct vm_exit *vexit)
{
        reading_t readings[2];
        uint_t nread = 0;
        uint_t nrepeat = 0;

        const uint_t margin_ticks = MAX(1, LAPIC_TARGET_TICKS / 5000);
        const uint_t margin_ppm = 400;

        do {
                const enum vm_exit_kind kind =
                    test_run_vcpu(vcpu, ventry, vexit);
                if (kind == VEK_REENTR) {
                        continue;
                } else if (kind != VEK_UNHANDLED) {
                        test_fail_vmexit(vexit);
                }

                /* input the divisor */
                if (vexit_match_inout(vexit, true, IOP_TEST_PARAM, 4, NULL)) {
                        ventry_fulfill_inout(vexit, ventry, divisor);
                        continue;
                }

                uint32_t v;
                if (vexit_match_inout(vexit, false, IOP_TEST_VALUE, 4, &v)) {
                        readings[nread].when = gethrtime();
                        readings[nread].value = v;
                        ventry_fulfill_inout(vexit, ventry, 0);

                        nread++;
                        if (nread != 2) {
                                continue;
                        }

                        if (check_reading(readings[0], readings[1], divisor,
                            margin_ticks, margin_ppm)) {
                                (void) printf("good result\n");
                                return;
                        } else {
                                nrepeat++;
                                if (nrepeat < 3) {
                                        nread = 0;
                                        (void) printf("retry %u\n", nrepeat);
                                        continue;
                                }
                                test_fail_msg("bad result after %u retries\n",
                                    nrepeat);
                        }
                } else {
                        test_fail_vmexit(vexit);
                }
        } while (true);
}

int
main(int argc, char *argv[])
{
        const char *test_suite_name = basename(argv[0]);
        struct vmctx *ctx = NULL;
        struct vcpu *vcpu;
        int err;

        ctx = test_initialize(test_suite_name);

        if ((vcpu = vm_vcpu_open(ctx, 0)) == NULL) {
                test_fail_errno(errno, "Could not open vcpu0");
        }

        err = test_setup_vcpu(vcpu, MEM_LOC_PAYLOAD, MEM_LOC_STACK);
        if (err != 0) {
                test_fail_errno(err, "Could not initialize vcpu0");
        }

        struct vm_entry ventry = { 0 };
        struct vm_exit vexit = { 0 };

        test_for_divisor(vcpu, 2, &ventry, &vexit);
        test_for_divisor(vcpu, 4, &ventry, &vexit);
        test_for_divisor(vcpu, 16, &ventry, &vexit);
        test_pass();
        return (0);
}