virtio-net

// vi:ft=cpp
/* SPDX-License-Identifier: MIT */
/*
 * Copyright (C) 2022 Kernkonzept GmbH.
 * Author(s): Stephan Gerhold <stephan.gerhold@kernkonzept.com>
 */
#pragma once
 
#include <cstring>
#include <functional>
 
#include <l4/cxx/exceptions>
#include <l4/cxx/minmax>
#include <l4/re/dataspace>
#include <l4/re/env>
#include <l4/re/error_helper>
#include <l4/re/util/unique_cap>
#include <l4/sys/consts.h>
 
#include <l4/l4virtio/client/l4virtio>
#include <l4/l4virtio/l4virtio>
#include <l4/l4virtio/virtio_net.h>
#include <l4/l4virtio/virtqueue>
 
namespace L4virtio { namespace Driver {
 
class Virtio_net_device : public L4virtio::Driver::Device
{
public:
  struct Packet
  {
    l4virtio_net_header_t hdr;
    l4_uint8_t data[1500 + 14]; /* MTU + Ethernet header */
  };
 
  int rx_queue_size() const
  { return max_queue_size(0); }
 
  int tx_queue_size() const
  { return max_queue_size(1); }
 
  void setup_device(L4::Cap<L4virtio::Device> srvcap)
  {
    // Contact device.
    driver_connect(srvcap);
 
    if (_config->device != L4VIRTIO_ID_NET)
      L4Re::chksys(-L4_ENODEV, "Device is not a network device.");
 
    if (_config->num_queues < 2)
      L4Re::chksys(-L4_EINVAL, "Invalid number of queues reported.");
 
    auto rxqsz = rx_queue_size();
    auto txqsz = tx_queue_size();
 
    // Allocate memory for RX/TX queue and RX/TX packet buffers
    auto rxqoff = 0;
    auto txqoff = l4_round_size(rxqoff + rxqsz * _rxq.total_size(rxqsz),
                                L4virtio::Virtqueue::Desc_align);
    auto rxpktoff = l4_round_size(txqoff + txqsz * _txq.total_size(txqsz),
                                  L4virtio::Virtqueue::Desc_align);
    auto txpktoff = rxpktoff + rxqsz * sizeof(Packet);
    auto totalsz = txpktoff + txqsz * sizeof(Packet);
 
    _queue_ds = L4Re::chkcap(L4Re::Util::make_unique_cap<L4Re::Dataspace>(),
                             "Allocate queue dataspace capability");
    auto *e = L4Re::Env::env();
    L4Re::chksys(e->mem_alloc()->alloc(totalsz, _queue_ds.get(),
                                       L4Re::Mem_alloc::Continuous
                                       | L4Re::Mem_alloc::Pinned),
                 "Allocate memory for virtio structures");
 
    L4Re::chksys(e->rm()->attach(&_queue_region, totalsz,
                                 L4Re::Rm::F::Search_addr | L4Re::Rm::F::RW,
                                 L4::Ipc::make_cap_rw(_queue_ds.get()), 0,
                                 L4_PAGESHIFT),
                 "Attach dataspace for virtio structures");
 
    l4_uint64_t devaddr;
    L4Re::chksys(register_ds(_queue_ds.get(), 0, totalsz, &devaddr),
                 "Register queue dataspace with device");
 
    _rxq.init_queue(rxqsz, _queue_region.get() + rxqoff);
    _txq.init_queue(txqsz, _queue_region.get() + txqoff);
 
    config_queue(0, rxqsz, devaddr + rxqoff,
                 devaddr + rxqoff + _rxq.avail_offset(),
                 devaddr + rxqoff + _rxq.used_offset());
    config_queue(1, txqsz, devaddr + txqoff,
                 devaddr + txqoff + _txq.avail_offset(),
                 devaddr + txqoff + _txq.used_offset());
 
    _rxpkts = reinterpret_cast<Packet*>(_queue_region.get() + rxpktoff);
    _txpkts = reinterpret_cast<Packet*>(_queue_region.get() + txpktoff);
 
    // Prepare descriptors to save work later
    for (l4_uint16_t descno = 0; descno < rxqsz; ++descno)
      {
        auto &desc = _rxq.desc(descno);
        desc.addr = L4virtio::Ptr<void>(devaddr + rxpktoff +
                                        descno * sizeof(Packet));
        desc.len = sizeof(Packet);
        desc.flags.write() = 1;
      }
    for (l4_uint16_t descno = 0; descno < txqsz; ++descno)
      {
        auto &desc = _txq.desc(descno);
        desc.addr = L4virtio::Ptr<void>(devaddr + txpktoff +
                                        descno * sizeof(Packet));
        desc.len = sizeof(Packet);
      }
 
    // Finish handshake with device
    l4virtio_set_feature(_config->driver_features_map,
                         L4VIRTIO_FEATURE_VERSION_1);
    l4virtio_set_feature(_config->driver_features_map, L4VIRTIO_NET_F_MAC);
    driver_acknowledge();
  }
 
  l4virtio_net_config_t const &device_config() const
  {
    return *_config->device_config<l4virtio_net_config_t>();
  }
 
  Packet &rx_pkt(l4_uint16_t descno)
  {
    if (descno >= _rxq.num())
      throw L4::Bounds_error("Invalid used descriptor number in RX queue");
    return _rxpkts[descno];
  }
 
  l4_uint16_t wait_rx(l4_uint32_t *len = nullptr)
  {
    auto descno = L4Re::chksys(wait_for_next_used(_rxq, len), "Wait for RX");
    if (len)
      // Ensure that the length provided by the device in wait_for_next_used()
      // is not larger than the buffer and subtract the length of the header.
      *len = cxx::min(*len - sizeof(_rxpkts[0].hdr), sizeof(_rxpkts[0].data));
    return descno;
  }
 
  void finish_rx(l4_uint16_t descno)
  {
    _rxq.free_descriptor(descno, descno);
  }
 
  void queue_rx()
  {
    l4_uint16_t descno;
    while ((descno = _rxq.alloc_descriptor()) != Virtqueue::Eoq)
      _rxq.enqueue_descriptor(descno);
    notify(_rxq);
  }
 
  bool tx(std::function<l4_uint32_t(Packet&)> prepare)
  {
    auto descno = _txq.alloc_descriptor();
    if (descno == Virtqueue::Eoq)
      {
        // Try again after cleaning old descriptors that have already been used
        free_used_tx_descriptors();
        descno = _txq.alloc_descriptor();
        if (descno == Virtqueue::Eoq)
          return false;
      }
 
    auto &pkt = _txpkts[descno];
    auto &desc = _txq.desc(descno);
    desc.len = sizeof(pkt.hdr) + prepare(pkt);
    send(_txq, descno);
    return true;
  }
 
private:
  void free_used_tx_descriptors()
  {
    l4_uint16_t used;
    while ((used = _txq.find_next_used()) != Virtqueue::Eoq)
      {
        if (used >= _txq.num())
          throw L4::Bounds_error("Invalid used descriptor number in TX queue");
        _txq.free_descriptor(used, used);
      }
  }
 
private:
  L4Re::Util::Unique_cap<L4Re::Dataspace> _queue_ds;
  L4Re::Rm::Unique_region<l4_uint8_t *> _queue_region;
  L4virtio::Driver::Virtqueue _rxq, _txq;
  Packet *_rxpkts, *_txpkts;
};
 
} }