// Copyright 2018 The Chromium OS Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE-BSD-3-Clause file.
//
// Copyright © 2019 Intel Corporation
//
// SPDX-License-Identifier: Apache-2.0 AND BSD-3-Clause

use crate::{ActivateError, ActivateResult, Error, Queue};
use libc::EFD_NONBLOCK;
use std::collections::HashMap;
use std::io::Write;
use std::num::Wrapping;
use std::sync::{
    atomic::{AtomicBool, Ordering},
    Arc, Barrier,
};
use std::thread;
use vm_memory::{GuestAddress, GuestMemoryAtomic, GuestMemoryMmap, GuestUsize};
use vm_migration::{MigratableError, Pausable};
use vm_virtio::VirtioDeviceType;
use vmm_sys_util::eventfd::EventFd;

pub enum VirtioInterruptType {
    Config,
    Queue,
}

pub trait VirtioInterrupt: Send + Sync {
    fn trigger(
        &self,
        int_type: &VirtioInterruptType,
        queue: Option<&Queue>,
    ) -> std::result::Result<(), std::io::Error>;
    fn notifier(&self, _int_type: &VirtioInterruptType, _queue: Option<&Queue>) -> Option<EventFd> {
        None
    }
}

#[derive(Clone)]
pub struct UserspaceMapping {
    pub host_addr: u64,
    pub mem_slot: u32,
    pub addr: GuestAddress,
    pub len: GuestUsize,
    pub mergeable: bool,
}

#[derive(Clone)]
pub struct VirtioSharedMemory {
    pub offset: u64,
    pub len: u64,
}

#[derive(Clone)]
pub struct VirtioSharedMemoryList {
    pub host_addr: u64,
    pub mem_slot: u32,
    pub addr: GuestAddress,
    pub len: GuestUsize,
    pub region_list: Vec<VirtioSharedMemory>,
}

/// Trait for virtio devices to be driven by a virtio transport.
///
/// The lifecycle of a virtio device is to be moved to a virtio transport, which will then query the
/// device. Once the guest driver has configured the device, `VirtioDevice::activate` will be called
/// and all the events, memory, and queues for device operation will be moved into the device.
/// Optionally, a virtio device can implement device reset in which it returns said resources and
/// resets its internal.
pub trait VirtioDevice: Send {
    /// The virtio device type.
    fn device_type(&self) -> u32;

    /// The maximum size of each queue that this device supports.
    fn queue_max_sizes(&self) -> &[u16];

    /// The set of feature bits that this device supports.
    fn features(&self) -> u64 {
        0
    }

    /// Acknowledges that this set of features should be enabled.
    fn ack_features(&mut self, value: u64) {
        let _ = value;
    }

    /// Reads this device configuration space at `offset`.
    fn read_config(&self, _offset: u64, _data: &mut [u8]) {
        warn!(
            "No readable configuration fields for {}",
            VirtioDeviceType::from(self.device_type())
        );
    }

    /// Writes to this device configuration space at `offset`.
    fn write_config(&mut self, _offset: u64, _data: &[u8]) {
        warn!(
            "No writable configuration fields for {}",
            VirtioDeviceType::from(self.device_type())
        );
    }

    /// Activates this device for real usage.
    fn activate(
        &mut self,
        mem: GuestMemoryAtomic<GuestMemoryMmap>,
        interrupt_evt: Arc<dyn VirtioInterrupt>,
        queues: Vec<Queue>,
        queue_evts: Vec<EventFd>,
    ) -> ActivateResult;

    /// Optionally deactivates this device and returns ownership of the guest memory map, interrupt
    /// event, and queue events.
    fn reset(&mut self) -> Option<Arc<dyn VirtioInterrupt>> {
        None
    }

    /// Returns the list of shared memory regions required by the device.
    fn get_shm_regions(&self) -> Option<VirtioSharedMemoryList> {
        None
    }

    /// Updates the list of shared memory regions required by the device.
    fn set_shm_regions(
        &mut self,
        _shm_regions: VirtioSharedMemoryList,
    ) -> std::result::Result<(), Error> {
        std::unimplemented!()
    }

    fn iommu_translate(&self, addr: u64) -> u64 {
        addr
    }

    /// Some devices may need to do some explicit shutdown work. This method
    /// may be implemented to do this. The VMM should call shutdown() on
    /// every device as part of shutting down the VM. Acting on the device
    /// after a shutdown() can lead to unpredictable results.
    fn shutdown(&mut self) {}

    fn update_memory(&mut self, _mem: &GuestMemoryMmap) -> std::result::Result<(), Error> {
        Ok(())
    }

    /// Returns the list of userspace mappings associated with this device.
    fn userspace_mappings(&self) -> Vec<UserspaceMapping> {
        Vec::new()
    }

    /// Return the counters that this device exposes
    fn counters(&self) -> Option<HashMap<&'static str, Wrapping<u64>>> {
        None
    }

    /// Helper to allow common implementation of read_config
    fn read_config_from_slice(&self, config: &[u8], offset: u64, mut data: &mut [u8]) {
        let config_len = config.len() as u64;
        let data_len = data.len() as u64;
        if offset + data_len > config_len {
            error!(
                "Out-of-bound access to configuration: config_len = {} offset = {:x} length = {} for {}",
                config_len,
                offset,
                data_len,
                self.device_type()
            );
            return;
        }
        if let Some(end) = offset.checked_add(data.len() as u64) {
            data.write_all(&config[offset as usize..std::cmp::min(end, config_len) as usize])
                .unwrap();
        }
    }

    /// Helper to allow common implementation of write_config
    fn write_config_helper(&self, config: &mut [u8], offset: u64, data: &[u8]) {
        let config_len = config.len() as u64;
        let data_len = data.len() as u64;
        if offset + data_len > config_len {
            error!(
                    "Out-of-bound access to configuration: config_len = {} offset = {:x} length = {} for {}",
                    config_len,
                    offset,
                    data_len,
                    self.device_type()
                );
            return;
        }

        if let Some(end) = offset.checked_add(config.len() as u64) {
            let mut offset_config =
                &mut config[offset as usize..std::cmp::min(end, config_len) as usize];
            offset_config.write_all(data).unwrap();
        }
    }
}

/// Trait providing address translation the same way a physical DMA remapping
/// table would provide translation between an IOVA and a physical address.
/// The goal of this trait is to be used by virtio devices to perform the
/// address translation before they try to read from the guest physical address.
/// On the other side, the implementation itself should be provided by the code
/// emulating the IOMMU for the guest.
pub trait DmaRemapping: Send + Sync {
    fn translate(&self, id: u32, addr: u64) -> std::result::Result<u64, std::io::Error>;
}

/// Structure to handle device state common to all devices
#[derive(Default)]
pub struct VirtioCommon {
    pub avail_features: u64,
    pub acked_features: u64,
    pub kill_evt: Option<EventFd>,
    pub interrupt_cb: Option<Arc<dyn VirtioInterrupt>>,
    pub queue_evts: Option<Vec<EventFd>>,
    pub pause_evt: Option<EventFd>,
    pub paused: Arc<AtomicBool>,
    pub paused_sync: Option<Arc<Barrier>>,
    pub epoll_threads: Option<Vec<thread::JoinHandle<()>>>,
    pub queue_sizes: Vec<u16>,
    pub device_type: u32,
    pub min_queues: u16,
}

impl VirtioCommon {
    pub fn feature_acked(&self, feature: u64) -> bool {
        self.acked_features & 1 << feature == 1 << feature
    }

    pub fn ack_features(&mut self, value: u64) {
        let mut v = value;
        // Check if the guest is ACK'ing a feature that we didn't claim to have.
        let unrequested_features = v & !self.avail_features;
        if unrequested_features != 0 {
            warn!("Received acknowledge request for unknown feature.");

            // Don't count these features as acked.
            v &= !unrequested_features;
        }
        self.acked_features |= v;
    }

    pub fn activate(
        &mut self,
        queues: &[Queue],
        queue_evts: &[EventFd],
        interrupt_cb: &Arc<dyn VirtioInterrupt>,
    ) -> ActivateResult {
        if queues.len() != queue_evts.len() {
            error!(
                "Cannot activate: length mismatch: queue_evts={} queues={}",
                queue_evts.len(),
                queues.len()
            );
            return Err(ActivateError::BadActivate);
        }

        if queues.len() < self.min_queues.into() {
            error!(
                "Number of enabled queues lower tham min: {} vs {}",
                queues.len(),
                self.min_queues
            );
            return Err(ActivateError::BadActivate);
        }

        let kill_evt = EventFd::new(EFD_NONBLOCK).map_err(|e| {
            error!("failed creating kill EventFd: {}", e);
            ActivateError::BadActivate
        })?;
        self.kill_evt = Some(kill_evt);

        let pause_evt = EventFd::new(EFD_NONBLOCK).map_err(|e| {
            error!("failed creating pause EventFd: {}", e);
            ActivateError::BadActivate
        })?;
        self.pause_evt = Some(pause_evt);

        // Save the interrupt EventFD as we need to return it on reset
        // but clone it to pass into the thread.
        self.interrupt_cb = Some(interrupt_cb.clone());

        let mut tmp_queue_evts: Vec<EventFd> = Vec::new();
        for queue_evt in queue_evts.iter() {
            // Save the queue EventFD as we need to return it on reset
            // but clone it to pass into the thread.
            tmp_queue_evts.push(queue_evt.try_clone().map_err(|e| {
                error!("failed to clone queue EventFd: {}", e);
                ActivateError::BadActivate
            })?);
        }
        self.queue_evts = Some(tmp_queue_evts);
        Ok(())
    }

    pub fn reset(&mut self) -> Option<Arc<dyn VirtioInterrupt>> {
        // We first must resume the virtio thread if it was paused.
        if self.pause_evt.take().is_some() {
            self.resume().ok()?;
        }

        if let Some(kill_evt) = self.kill_evt.take() {
            // Ignore the result because there is nothing we can do about it.
            let _ = kill_evt.write(1);
        }

        if let Some(mut threads) = self.epoll_threads.take() {
            for t in threads.drain(..) {
                if let Err(e) = t.join() {
                    error!("Error joining thread: {:?}", e);
                }
            }
        }

        // Return the interrupt
        Some(self.interrupt_cb.take().unwrap())
    }
}

impl Pausable for VirtioCommon {
    fn pause(&mut self) -> std::result::Result<(), MigratableError> {
        debug!(
            "Pausing virtio-{}",
            VirtioDeviceType::from(self.device_type)
        );
        self.paused.store(true, Ordering::SeqCst);
        if let Some(pause_evt) = &self.pause_evt {
            pause_evt
                .write(1)
                .map_err(|e| MigratableError::Pause(e.into()))?;

            // Wait for all threads to acknowledge the pause before going
            // any further. This is exclusively performed when pause_evt
            // eventfd is Some(), as this means the virtio device has been
            // activated. One specific case where the device can be paused
            // while it hasn't been yet activated is snapshot/restore.
            self.paused_sync.as_ref().unwrap().wait();
        }

        Ok(())
    }

    fn resume(&mut self) -> std::result::Result<(), MigratableError> {
        debug!(
            "Resuming virtio-{}",
            VirtioDeviceType::from(self.device_type)
        );
        self.paused.store(false, Ordering::SeqCst);
        if let Some(epoll_threads) = &self.epoll_threads {
            for t in epoll_threads.iter() {
                t.thread().unpark();
            }
        }

        Ok(())
    }
}