/*
 * 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 2023 Oxide Computer Company
 */

/*
 * Test guest frequency control
 *
 * Note: requires `vmm_allow_state_writes` to be set, and only on AMD
 */

#include <unistd.h>
#include <stdlib.h>
#include <libgen.h>
#include <errno.h>
#include <err.h>

#include <sys/time.h>
#include <sys/vmm_data.h>
#include <sys/vmm_dev.h>
#include <vmmapi.h>

#include "common.h"
#include "in_guest.h"

#define PPM_MARGIN      200

typedef struct tsc_reading {
        hrtime_t when;
        uint64_t tsc;
} tsc_reading_t;

static bool
check_reading(tsc_reading_t r1, tsc_reading_t r2, uint64_t guest_freq,
    uint64_t min_ticks, uint64_t tick_margin, uint32_t ppm_margin)
{
        hrtime_t time_delta = r2.when - r1.when;
        uint64_t tick_delta = r2.tsc - r1.tsc;

        /* check that number of ticks seen is valid */
        if (tick_delta < min_ticks) {
                test_fail_msg("inadequate passage of guest TSC ticks %u < %u\n",
                    tick_delta, min_ticks);
        } else if ((tick_delta - min_ticks) > tick_margin) {
                (void) printf("%u ticks outside margin %u\n", tick_delta,
                    min_ticks + tick_margin);
                return (false);
        }

        /* compute ppm error and validate */
        hrtime_t time_target = (tick_delta * NANOSEC) / guest_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("%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);
}

void
do_freq_test(uint64_t guest_freq, uint8_t per_sec, uint8_t seconds,
    const int vmfd, struct vcpu *vcpu, struct vdi_time_info_v1 *src)
{
        /* configure the guest to have the desired frequency */
        struct vdi_time_info_v1 time_info = {
                .vt_guest_freq = guest_freq,
                .vt_guest_tsc = src->vt_guest_tsc,
                .vt_boot_hrtime = src->vt_boot_hrtime,
                .vt_hrtime = src->vt_hrtime,
                .vt_hres_sec = src->vt_hres_sec,
                .vt_hres_ns = src->vt_hres_ns,
        };
        struct vm_data_xfer xfer = {
                .vdx_class = VDC_VMM_TIME,
                .vdx_version = 1,
                .vdx_len = sizeof (struct vdi_time_info_v1),
                .vdx_data = &time_info,
        };
        if (ioctl(vmfd, VM_DATA_WRITE, &xfer) != 0) {
                int error;
                error = errno;
                if (error == EPERM) {
                        warn("VMM_DATA_WRITE got EPERM: is "
                            "vmm_allow_state_writes set?");
                }
                errx(EXIT_FAILURE, "VMM_DATA_WRITE of time info failed");
        }


        /*
         * Run the test:
         * - ask the guest to report the TSC every 1/per_sec seconds, in terms
         *   of guest ticks
         * - collect readings for `seconds` seconds, along with host hrtime
         * - to avoid additional latency in the readings, process readings at
         *   the end: check for error in the number of ticks reported and the
         *   ppm based on host hrtime
         */
        uint64_t guest_ticks = guest_freq / per_sec;
        const uint32_t nreadings = per_sec * seconds + 1;
        tsc_reading_t tsc_readings[nreadings];

        /* 5 percent margin */
        const uint32_t tick_margin = guest_ticks / 20;

        bool half_read = false;
        uint64_t cur_tsc;
        uint32_t count = 0;

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

        do {
                if (count >= nreadings) {
                        /* test completed: check results */
                        for (int i = 1; i < nreadings; i++) {
                                if (!check_reading(tsc_readings[i-1],
                                    tsc_readings[i], guest_freq, guest_ticks,
                                    tick_margin, PPM_MARGIN)) {
                                        test_fail_msg("freq test failed");
                                }
                        }
                        break;
                }

                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);
                }

                uint32_t val;
                if (vexit_match_inout(&vexit, true, IOP_TEST_VALUE, 4,
                    &val)) {
                        /* test setup: tell guest how often to report its tsc */
                        ventry_fulfill_inout(&vexit, &ventry, guest_ticks);

                } else if (vexit_match_inout(&vexit, false, IOP_TEST_VALUE, 4,
                    &val)) {
                        /*
                         * Get reported guest TSC in two 32-bit parts, with the
                         * lower bits coming in first.
                         */
                        if (!half_read) {
                                /* lower bits */
                                cur_tsc = val;
                                half_read = true;
                                ventry_fulfill_inout(&vexit, &ventry, 0);
                        } else {
                                /* upper bits */
                                cur_tsc |= ((uint64_t)val << 32);

                                tsc_readings[count].when = gethrtime();
                                tsc_readings[count].tsc = cur_tsc;

                                half_read = false;
                                cur_tsc = 0;
                                count++;

                                ventry_fulfill_inout(&vexit, &ventry, 0);
                        }
                } 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");
        }

        const int vmfd = vm_get_device_fd(ctx);
        const bool is_svm = cpu_vendor_amd();

        if (!is_svm) {
                test_fail_msg("intel not supported\n");
        }

        /* Read time data to get baseline guest time values */
        struct vdi_time_info_v1 time_info;
        struct vm_data_xfer xfer = {
                .vdx_class = VDC_VMM_TIME,
                .vdx_version = 1,
                .vdx_len = sizeof (struct vdi_time_info_v1),
                .vdx_data = &time_info,
        };
        if (ioctl(vmfd, VM_DATA_READ, &xfer) != 0) {
                errx(EXIT_FAILURE, "VMM_DATA_READ of time info failed");
        }
        uint64_t host_freq = time_info.vt_guest_freq;
        uint64_t guest_freq = host_freq;

        /* measure each test frequency 10x per sec, for 1 second */
        const uint8_t per_sec = 10;
        const uint8_t seconds = 1;

        /* 2x host frequency */
        guest_freq = host_freq * 2;
        (void) printf("testing 2x host_freq: guest_freq=%lu, host_freq=%lu\n",
            guest_freq, host_freq);
        do_freq_test(guest_freq, per_sec, seconds, vmfd, vcpu, &time_info);

        /* reset guest */
        vm_vcpu_close(vcpu);
        test_cleanup(false);
        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");
        }


        /* 0.5x host frequency */
        guest_freq = host_freq / 2;
        (void) printf("testing 0.5x host_freq: guest_freq=%lu, host_freq=%lu\n",
            guest_freq, host_freq);
        do_freq_test(guest_freq, per_sec, seconds, vmfd, vcpu, &time_info);

        /* reset guest */
        vm_vcpu_close(vcpu);
        test_cleanup(false);
        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");
        }


        /* 1/3 host frequency */
        guest_freq = host_freq / 3;
        (void) printf("testing 1/3 host_freq: guest_freq=%lu, host_freq=%lu\n",
            guest_freq, host_freq);
        do_freq_test(guest_freq, per_sec, seconds, vmfd, vcpu, &time_info);

        /* reset guest */
        vm_vcpu_close(vcpu);
        test_cleanup(false);
        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");
        }


        /* 1x host frequency */
        guest_freq = host_freq;
        (void) printf("testing 1x host_freq: guest_freq=%lu, host_freq=%lu\n",
            guest_freq, host_freq);
        do_freq_test(guest_freq, per_sec, seconds, vmfd, vcpu, &time_info);

        test_pass();
}