/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2025 Ruslan Bukin <br@bsdpad.com>
 *
 * This software was developed by the University of Cambridge Computer
 * Laboratory (Department of Computer Science and Technology) under Innovate
 * UK project 105694, "Digital Security by Design (DSbD) Technology Platform
 * Prototype".
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/smp.h>
#include <sys/kernel.h>
#include <sys/malloc.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/bus.h>

#include <machine/vmm.h>

#include <dev/vmm/vmm_vm.h>

#include "riscv.h"
#include "vmm_fence.h"

static bool
vmm_fence_dequeue(struct hypctx *hypctx, struct vmm_fence *new_fence)
{
        struct vmm_fence *queue;
        struct vmm_fence *fence;

        mtx_lock_spin(&hypctx->fence_queue_mtx);
        queue = hypctx->fence_queue;
        fence = &queue[hypctx->fence_queue_head];
        if (fence->type != VMM_RISCV_FENCE_INVALID) {
                *new_fence = *fence;
                fence->type = VMM_RISCV_FENCE_INVALID;
                hypctx->fence_queue_head =
                    (hypctx->fence_queue_head + 1) % VMM_FENCE_QUEUE_SIZE;
        } else {
                mtx_unlock_spin(&hypctx->fence_queue_mtx);
                return (false);
        }
        mtx_unlock_spin(&hypctx->fence_queue_mtx);

        return (true);
}

static bool
vmm_fence_enqueue(struct hypctx *hypctx, struct vmm_fence *new_fence)
{
        struct vmm_fence *queue;
        struct vmm_fence *fence;

        mtx_lock_spin(&hypctx->fence_queue_mtx);
        queue = hypctx->fence_queue;
        fence = &queue[hypctx->fence_queue_tail];
        if (fence->type == VMM_RISCV_FENCE_INVALID) {
                *fence = *new_fence;
                hypctx->fence_queue_tail =
                    (hypctx->fence_queue_tail + 1) % VMM_FENCE_QUEUE_SIZE;
        } else {
                mtx_unlock_spin(&hypctx->fence_queue_mtx);
                return (false);
        }
        mtx_unlock_spin(&hypctx->fence_queue_mtx);

        return (true);
}

static void
vmm_fence_process_one(struct vmm_fence *fence)
{
        uint64_t va;

        KASSERT(fence->type == VMM_RISCV_FENCE_VMA ||
            fence->type == VMM_RISCV_FENCE_VMA_ASID,
            ("%s: wrong fence type %d", __func__, fence->type));

        switch (fence->type) {
        case VMM_RISCV_FENCE_VMA:
                for (va = fence->start; va < fence->start + fence->size;
                    va += PAGE_SIZE)
                        sfence_vma_page(va);
                break;
        case VMM_RISCV_FENCE_VMA_ASID:
                if ((fence->start == 0 && fence->size == 0) ||
                    fence->size == -1)
                        sfence_vma_asid(fence->asid);
                else
                        for (va = fence->start; va < fence->start + fence->size;
                            va += PAGE_SIZE)
                                sfence_vma_asid_page(fence->asid, va);
                break;
        default:
                break;
        }
}

void
vmm_fence_process(struct hypctx *hypctx)
{
        struct vmm_fence fence;
        int pending;

        pending = atomic_readandclear_32(&hypctx->fence_req);

        KASSERT((pending & ~(FENCE_REQ_I | FENCE_REQ_VMA)) == 0,
            ("wrong fence bit mask"));

        if (pending & FENCE_REQ_I)
                fence_i();

        if (pending & FENCE_REQ_VMA)
                sfence_vma();

        while (vmm_fence_dequeue(hypctx, &fence) == true)
                vmm_fence_process_one(&fence);
}

void
vmm_fence_add(struct vm *vm, cpuset_t *cpus, struct vmm_fence *fence)
{
        struct hypctx *hypctx;
        cpuset_t running_cpus;
        struct vcpu *vcpu;
        uint16_t maxcpus;
        int hostcpu;
        bool enq;
        int i;

        CPU_ZERO(&running_cpus);

        maxcpus = vm_get_maxcpus(vm);
        for (i = 0; i < maxcpus; i++) {
                if (!CPU_ISSET(i, cpus))
                        continue;
                vcpu = vm_vcpu(vm, i);
                hypctx = vcpu_get_cookie(vcpu);

                enq = false;

                /* No need to enqueue fences i and vma global. */
                switch (fence->type) {
                case VMM_RISCV_FENCE_I:
                        atomic_set_32(&hypctx->fence_req, FENCE_REQ_I);
                        break;
                case VMM_RISCV_FENCE_VMA:
                        if ((fence->start == 0 && fence->size == 0) ||
                            fence->size == -1)
                                atomic_set_32(&hypctx->fence_req,
                                    FENCE_REQ_VMA);
                        else
                                enq = true;
                        break;
                case VMM_RISCV_FENCE_VMA_ASID:
                        enq = true;
                        break;
                default:
                        KASSERT(0, ("%s: wrong fence type %d", __func__,
                            fence->type));
                        break;
                }

                /*
                 * Try to enqueue. In case of failure use more conservative
                 * request.
                 */
                if (enq)
                        if (vmm_fence_enqueue(hypctx, fence) == false)
                                atomic_set_32(&hypctx->fence_req,
                                    FENCE_REQ_VMA);

                mb();

                if (vcpu_is_running(vcpu, &hostcpu))
                        CPU_SET(hostcpu, &running_cpus);
        }

        /*
         * Interrupt other cores. On reception of IPI they will leave guest.
         * On entry back to the guest they will process fence request.
         *
         * If vcpu migrates to another cpu right here, it should process
         * all fences on entry to the guest as well.
         */
        if (!CPU_EMPTY(&running_cpus))
                smp_rendezvous_cpus(running_cpus, NULL, NULL, NULL, NULL);
}