l4virtio

// vi:ft=cpp
/* SPDX-License-Identifier: GPL-2.0-only or License-Ref-kk-custom */
/*
 * Copyright (C) 2014-2022 Kernkonzept GmbH.
 * Author(s): Alexander Warg <alexander.warg@kernkonzept.com>
 *            Manuel von Oltersdorff-Kalettka <manuel.kalettka@kernkonzept.com>
 *
 */
#pragma once
 
#include <algorithm>
#include <limits.h>
#include <memory>
#include <vector>
 
#include <l4/re/dataspace>
#include <l4/re/util/debug>
#include <l4/re/env>
#include <l4/re/error_helper>
#include <l4/re/rm>
#include <l4/re/util/cap_alloc>
#include <l4/re/util/shared_cap>
#include <l4/re/util/unique_cap>
 
#include <l4/sys/types.h>
#include <l4/re/util/meta>
 
#include <l4/cxx/bitfield>
#include <l4/cxx/utils>
#include <l4/cxx/unique_ptr>
 
#include <l4/sys/cxx/ipc_legacy>
 
#include "../l4virtio"
#include "virtio"
 
namespace L4virtio {
namespace Svr {
 
class Dev_config
{
public:
  typedef Dev_status Status;
  typedef Dev_features Features;
 
private:
  typedef L4Re::Rm::Unique_region< l4virtio_config_hdr_t*> Cfg_region;
  typedef L4Re::Util::Shared_cap<L4Re::Dataspace> Cfg_cap;
 
  l4_uint32_t _vendor, _device, _qoffset, _nqueues;
  l4_uint32_t _host_features[sizeof(l4virtio_config_hdr_t::dev_features_map)
                             / sizeof(l4_uint32_t)];
  Cfg_cap _ds;
  Cfg_region _config;
  l4_addr_t _ds_offset = 0;
 
  Status _status{0}; // status shadow, can be trusted by the device model
 
  static l4_uint32_t align(l4_uint32_t x)
  { return (x + 0xfU) & ~0xfU; }
 
  void attach_n_init_cfg(Cfg_cap const &cfg, l4_addr_t offset)
  {
    L4Re::chksys(L4Re::Env::env()->rm()->attach(&_config, L4_PAGESIZE,
                                                L4Re::Rm::F::Search_addr | L4Re::Rm::F::RW,
                                                L4::Ipc::make_cap_rw(cfg.get()),
                                                offset),
                 "Attach config space to local address space.");
 
    _config->generation = 0;
    memset(_config->driver_features_map, 0, sizeof(_config->driver_features_map));
    memset(_host_features, 0, sizeof(_host_features));
    set_host_feature(L4VIRTIO_FEATURE_VERSION_1);
    reset_hdr();
 
    _ds = cfg;
    _ds_offset = offset;
  }
 
protected:
  void volatile *get_priv_config() const
  {
    return l4virtio_device_config(_config.get());
  }
 
public:
 
  Dev_config(l4_uint32_t vendor, l4_uint32_t device,
             unsigned cfg_size, l4_uint32_t num_queues = 0)
  : _vendor(vendor), _device(device),
    _qoffset(0x100 + align(cfg_size)),
    _nqueues(num_queues)
  {
    using L4Re::Dataspace;
    using L4Re::chkcap;
    using L4Re::chksys;
 
    if (sizeof(l4virtio_config_queue_t) * _nqueues + _qoffset > L4_PAGESIZE)
      {
        // too many queues does not fit into our page
        _qoffset = 0;
        _nqueues = 0;
      }
 
    auto cfg = chkcap(L4Re::Util::make_shared_cap<Dataspace>());
    chksys(L4Re::Env::env()->mem_alloc()->alloc(L4_PAGESIZE, cfg.get()));
 
    attach_n_init_cfg(cfg, 0);
  }
 
  Dev_config(Cfg_cap const &cfg, l4_addr_t cfg_offset,
             l4_uint32_t vendor, l4_uint32_t device,
             unsigned cfg_size, l4_uint32_t num_queues = 0)
  : _vendor(vendor), _device(device),
    _qoffset(0x100 + align(cfg_size)),
    _nqueues(num_queues)
  {
    if (sizeof(l4virtio_config_queue_t) * _nqueues + _qoffset > L4_PAGESIZE)
      {
        // too many queues does not fit into our page
        _qoffset = 0;
        _nqueues = 0;
      }
 
    attach_n_init_cfg(cfg, cfg_offset);
  }
 
  void set_host_feature(unsigned feature)
  { l4virtio_set_feature(_host_features, feature); }
 
  void clear_host_feature(unsigned feature)
  { l4virtio_clear_feature(_host_features, feature); }
 
  bool get_host_feature(unsigned feature)
  { return l4virtio_get_feature(_host_features, feature); }
 
  bool get_guest_feature(unsigned feature)
  { return l4virtio_get_feature(_config->driver_features_map, feature); }
 
  l4_uint32_t &host_features(unsigned idx)
  { return _host_features[idx]; }
 
  l4_uint32_t host_features(unsigned idx) const
  { return _host_features[idx]; }
 
  l4_uint32_t guest_features(unsigned idx) const
  { return _config->driver_features_map[idx]; }
 
  l4_uint32_t negotiated_features(unsigned idx) const
  { return _config->driver_features_map[idx] & _host_features[idx]; }
 
  Status status() const { return _status; }
 
  l4_uint32_t get_cmd() const
  {
    return hdr()->cmd;
  }
 
  void reset_cmd()
  {
    const_cast<l4_uint32_t volatile &>(hdr()->cmd) = 0;
  }
 
  void set_status(Status status)
  {
    _status = status;
    const_cast<l4_uint32_t volatile &>(hdr()->status) = status.raw;
  }
 
  void set_device_needs_reset()
  {
    _status.device_needs_reset() = 1;
    const_cast<l4_uint32_t volatile &>(hdr()->status) = _status.raw;
  }
 
  bool change_queue_config(l4_uint32_t num_queues)
  {
    if (sizeof(l4virtio_config_queue_t) * num_queues + _qoffset > L4_PAGESIZE)
      // too many queues does not fit into our page
      return false;
 
    _nqueues = num_queues;
    reset_hdr(true);
    return true;
  }
 
  l4virtio_config_queue_t volatile const *qconfig(unsigned index) const
  {
    if (L4_UNLIKELY(_qoffset < sizeof (l4virtio_config_hdr_t)))
      return 0;
 
    if (L4_UNLIKELY(index >= _nqueues))
      return 0;
 
    return reinterpret_cast<l4virtio_config_queue_t const *>
      (reinterpret_cast<char *>(_config.get()) + _qoffset) + index;
  }
 
  void reset_hdr(bool inc_generation = false) const
  {
    _config->magic = L4VIRTIO_MAGIC;
    _config->version = 2;
    _config->device = _device;
    _config->vendor = _vendor;
    _config->status = 0;
    _config->irq_status = 0;
    _config->num_queues = _nqueues;
    _config->queues_offset = _qoffset;
 
    memcpy(_config->dev_features_map, _host_features,
           sizeof(_config->dev_features_map));
    wmb();
    if (inc_generation)
      ++_config->generation;
 
  }
 
  bool reset_queue(unsigned index, unsigned num_max,
                   bool inc_generation = false) const
  {
    l4virtio_config_queue_t volatile *qc;
    // this function is allowed to write to the device config
    qc = const_cast<l4virtio_config_queue_t volatile *>(qconfig(index));
    if (L4_UNLIKELY(qc == 0))
      return false;
 
    qc->num_max = num_max;
    qc->num = 0;
    qc->ready = 0;
    wmb();
    if (inc_generation)
      ++_config->generation;
 
    return true;
  }
 
  l4virtio_config_hdr_t const volatile *hdr() const
  { return _config.get(); }
 
  L4::Cap<L4Re::Dataspace> ds() const { return _ds.get(); }
 
  l4_addr_t ds_offset() const
  { return _ds_offset; }
};
 
 
template<typename PRIV_CONFIG>
class Dev_config_t : public Dev_config
{
public:
  typedef PRIV_CONFIG Priv_config;
 
  Dev_config_t(l4_uint32_t vendor, l4_uint32_t device,
               l4_uint32_t num_queues = 0)
  : Dev_config(vendor, device, sizeof(PRIV_CONFIG), num_queues)
  {}
 
  Dev_config_t(L4Re::Util::Shared_cap<L4Re::Dataspace> const &cfg,
               l4_addr_t cfg_offset, l4_uint32_t vendor, l4_uint32_t device,
               l4_uint32_t num_queues = 0)
  : Dev_config(cfg, cfg_offset, vendor, device, sizeof(PRIV_CONFIG),
               num_queues)
  {}
 
  Priv_config volatile *priv_config() const
  {
    return static_cast<Priv_config volatile *>(get_priv_config());
  }
 
};
 
struct No_custom_data {};
 
template <typename DATA>
class Driver_mem_region_t : public DATA
{
public:
  struct Flags
  {
    l4_uint32_t raw; 
    CXX_BITFIELD_MEMBER(0, 0, rw, raw); 
  };
 
private:
  typedef L4Re::Util::Unique_cap<L4Re::Dataspace> Ds_cap;
 
  l4_uint64_t _drv_base; 
  l4_uint64_t _trans_offset; 
  l4_umword_t _size;     
  Flags       _flags;    
 
  Ds_cap      _ds;       
  l4_addr_t   _ds_offset;
 
  L4Re::Rm::Unique_region<l4_addr_t> _local_base;
 
  template<typename T>
  T _local(l4_uint64_t addr) const
  {
    return (T)(addr - _trans_offset);
  }
 
public:
  Driver_mem_region_t() : _size(0) {}
 
  Driver_mem_region_t(l4_uint64_t drv_base, l4_umword_t size,
                      l4_addr_t offset, Ds_cap &&ds)
  : _drv_base(l4_trunc_page(drv_base)), _size(0),
    _ds_offset(l4_trunc_page(offset))
  {
    using L4Re::chksys;
    using L4Re::Env;
 
    L4Re::Dataspace::Stats ds_info = L4Re::Dataspace::Stats();
    // Sometimes we work with dataspaces that do not implement all dataspace
    // methods and return an error instead. An example of such a dataspace is
    // io's Vi::System_bus. We detect this case when the info method returns
    // -L4_ENOSYS and simply assume the dataspace is good for us.
    long err = ds->info(&ds_info);
    if (err >= 0)
      {
        l4_addr_t ds_size = l4_round_page(ds_info.size);
 
        if (ds_size < L4_PAGESIZE)
          chksys(-L4_EINVAL, "DS too small");
 
        if (_ds_offset >= ds_size)
          chksys(-L4_ERANGE, "offset larger than DS size");
 
        size = l4_round_page(size);
        if (size > ds_size)
          chksys(-L4_EINVAL, "size larger than DS size");
 
        if (_ds_offset > ds_size - size)
          chksys(-L4_EINVAL, "invalid offset or size");
 
        // overflow check
        if ((ULLONG_MAX - size) < _drv_base)
          chksys(-L4_EINVAL, "invalid size");
 
        _flags.rw() = (ds_info.flags & L4Re::Dataspace::F::W).raw != 0;
      }
    else if (err == -L4_ENOSYS)
      {
        _flags.rw() = true;
      }
    else
      {
        chksys(err, "getting data-space infos");
      }
 
    auto f = L4Re::Rm::F::Search_addr | L4Re::Rm::F::R;
    if (_flags.rw())
      f |= L4Re::Rm::F::W;
 
    // use a big alignment to save PT/TLB entries and kernel memory resources!
    chksys(Env::env()->rm()->attach(&_local_base, size, f,
                                    L4::Ipc::make_cap(ds.get(), _flags.rw()
                                                                ? L4_CAP_FPAGE_RW
                                                                : L4_CAP_FPAGE_RO),
                                    _ds_offset, L4_SUPERPAGESHIFT));
 
    _size = size;
    _ds = cxx::move(ds);
    _trans_offset = _drv_base - _local_base.get();
  }
 
  bool is_writable() const { return _flags.rw(); }
 
  Flags flags() const { return _flags; }
 
  bool empty() const
  { return _size == 0; }
 
  l4_uint64_t drv_base() const { return _drv_base; }
 
  void *local_base() const { return (void*)_local_base.get(); }
 
  l4_umword_t size() const { return _size; }
 
  l4_addr_t ds_offset() const { return _ds_offset; }
 
  L4::Cap<L4Re::Dataspace> ds() const { return _ds.get(); }
 
  bool contains(l4_uint64_t base, l4_umword_t size) const
  {
    if (base < _drv_base)
      return false;
 
    if (base > _drv_base + _size - 1)
      return false;
 
    if (size > _size)
      return false;
 
    if (base - _drv_base > _size - size)
      return false;
 
    return true;
  }
 
  template<typename T>
  T *local(Ptr<T> p) const
  { return _local<T*>(p.get()); }
};
 
typedef Driver_mem_region_t<No_custom_data> Driver_mem_region;
 
template <typename DATA>
class Driver_mem_list_t
{
public:
  typedef Driver_mem_region_t<DATA> Mem_region;
 
private:
  cxx::unique_ptr<Mem_region[]> _l;
  unsigned _max;
  unsigned _free;
 
public:
  typedef L4Re::Util::Unique_cap<L4Re::Dataspace> Ds_cap;
 
  Driver_mem_list_t() : _max(0), _free(0) {}
 
  void init(unsigned max)
  {
    _l = cxx::make_unique<Driver_mem_region_t<DATA>[]>(max);
    _max = max;
    _free = 0;
  }
 
  bool full() const
  { return _free == _max; }
 
  Mem_region const *add(l4_uint64_t drv_base, l4_umword_t size,
                        l4_addr_t offset, Ds_cap &&ds)
  {
    if (full())
      L4Re::chksys(-L4_ENOMEM);
 
    _l[_free++] = Mem_region(drv_base, size, offset, cxx::move(ds));
    return &_l[_free - 1];
  }
 
  void remove(Mem_region const *r)
  {
    if (r < &_l[0] || r >= &_l[_free])
      L4Re::chksys(-L4_ERANGE);
 
    unsigned idx = r - &_l[0];
 
    for (unsigned i = idx + 1; i < _free - 1; ++i)
      _l[i] = cxx::move(_l[i + 1]);
 
    _l[--_free] = Mem_region();
  }
 
  Mem_region *find(l4_uint64_t base, l4_umword_t size) const
  {
    return _find(base, size);
  }
 
  void load_desc(Virtqueue::Desc const &desc, Request_processor const *p,
                 Virtqueue::Desc const **table) const
  {
    Mem_region const *r = find(desc.addr.get(), desc.len);
    if (L4_UNLIKELY(!r))
      throw Bad_descriptor(p, Bad_descriptor::Bad_address);
 
    *table = static_cast<Virtqueue::Desc const *>(r->local(desc.addr));
  }
 
  void load_desc(Virtqueue::Desc const &desc, Request_processor const *p,
                 Mem_region const **data) const
  {
    Mem_region const *r = find(desc.addr.get(), desc.len);
    if (L4_UNLIKELY(!r))
      throw Bad_descriptor(p, Bad_descriptor::Bad_address);
 
    *data = r;
  }
 
  template<typename ARG>
  void load_desc(Virtqueue::Desc const &desc, Request_processor const *p,
                 ARG *data) const
  {
    Mem_region *r = find(desc.addr.get(), desc.len);
    if (L4_UNLIKELY(!r))
      throw Bad_descriptor(p, Bad_descriptor::Bad_address);
 
    *data = ARG(r, desc, p);
  }
 
private:
  Mem_region *_find(l4_uint64_t base, l4_umword_t size) const
  {
    for (unsigned i = 0; i < _free; ++i)
      if (_l[i].contains(base, size))
        return &_l[i];
    return 0;
  }
 
 
};
 
typedef Driver_mem_list_t<No_custom_data> Driver_mem_list;
 
template<typename DATA>
class Device_t
{
public:
  typedef Driver_mem_list_t<DATA> Mem_list;
 
protected:
  Mem_list _mem_info; 
 
private:
  Dev_config *_device_config; 
 
  using Ds_vector = std::vector<L4::Cap<L4Re::Dataspace>>;
  std::shared_ptr<Ds_vector const> _trusted_ds_caps;
 
  bool _trusted_ds_validation_enabled = false;
 
public:
  L4_RPC_LEGACY_DISPATCH(L4virtio::Device);
  template<typename IOS> int virtio_dispatch(unsigned r, IOS &ios)
  { return dispatch(r, ios); }
 
  virtual void reset() = 0;
 
  virtual bool check_features()
  { return true; }
 
  virtual bool check_queues() = 0;
 
  virtual int reconfig_queue(unsigned idx) = 0;
 
  virtual void register_single_driver_irq()
  { L4Re::chksys(-L4_ENOSYS, "Legacy single IRQ interface not implemented."); }
 
  virtual void trigger_driver_config_irq() const = 0;
 
  virtual L4::Cap<L4::Irq> device_notify_irq() const
  {
    L4Re::chksys(-L4_ENOSYS, "Legacy single IRQ interface not implemented.");
    return L4::Cap<L4::Irq>();
  }
 
  virtual void register_driver_irq(unsigned idx)
  {
    if (idx != 0)
      L4Re::chksys(-L4_ENOSYS, "Multi IRQ interface not implemented.");
 
    register_single_driver_irq();
  }
 
  virtual L4::Cap<L4::Irq> device_notify_irq(unsigned idx)
  {
    if (idx != 0)
      L4Re::chksys(-L4_ENOSYS, "Multi IRQ interface not implemented.");
 
    return device_notify_irq();
  }
 
  virtual unsigned num_events_supported() const
  { return 1; }
 
  virtual L4::Ipc_svr::Server_iface *server_iface() const = 0;
 
  Device_t(Dev_config *dev_config)
  : _device_config(dev_config)
  {}
 
  Mem_list const *mem_info() const
  { return &_mem_info; };
 
  long op_set_status(L4virtio::Device::Rights, unsigned status)
  { return _set_status(status); }
 
  long op_config_queue(L4virtio::Device::Rights, unsigned queue)
  {
    Dev_config::Status status = _device_config->status();
    if (status.fail_state() || !status.acked() || !status.driver())
      return -L4_EIO;
 
    return reconfig_queue(queue);
  }
 
  long op_register_ds(L4virtio::Device::Rights,
                      L4::Ipc::Snd_fpage ds_cap_fp, l4_uint64_t ds_base,
                      l4_umword_t offset, l4_umword_t sz)
  {
    L4Re::Util::Dbg()
      .printf("Registering dataspace from 0x%llx with %lu KiB, offset 0x%lx\n",
              ds_base, sz >> 10, offset);
 
    _check_n_init_shm(ds_cap_fp, ds_base, sz, offset);
 
    return 0;
  }
 
  long op_device_config(L4virtio::Device::Rights,
                        L4::Ipc::Cap<L4Re::Dataspace> &config_ds,
                        l4_addr_t &ds_offset)
  {
    L4Re::Util::Dbg()
      .printf("register client: host IRQ: %lx config DS: %lx\n",
              device_notify_irq().cap(), _device_config->ds().cap());
 
    config_ds = L4::Ipc::make_cap(_device_config->ds(), L4_CAP_FPAGE_RW);
    ds_offset = _device_config->ds_offset();
    return 0;
  }
 
  long op_device_notification_irq(L4virtio::Device::Rights,
                                  unsigned idx,
                                  L4::Ipc::Cap<L4::Triggerable> &irq)
  {
    auto cap = device_notify_irq(idx);
 
    if (!cap.is_valid())
      return -L4_EINVAL;
 
    irq = L4::Ipc::make_cap(cap, L4_CAP_FPAGE_RO);
    return L4_EOK;
  }
 
  int op_bind(L4::Icu::Rights, l4_umword_t idx, L4::Ipc::Snd_fpage irq_cap_fp)
  {
    if (idx >= num_events_supported())
      return -L4_ERANGE;
 
    if (!irq_cap_fp.cap_received())
      return -L4_EINVAL;
 
    register_driver_irq(idx);
 
    return L4_EOK;
  }
 
  int op_unbind(L4::Icu::Rights, l4_umword_t, L4::Ipc::Snd_fpage)
  {
    return -L4_ENOSYS;
  }
 
  int op_info(L4::Icu::Rights, L4::Icu::_Info &info)
  {
    info.features = 0;
    info.nr_irqs = num_events_supported();
    info.nr_msis = 0;
 
    return L4_EOK;
  }
 
  int op_msi_info(L4::Icu::Rights, l4_umword_t, l4_uint64_t, l4_icu_msi_info_t &)
  { return -L4_ENOSYS; }
 
  int op_mask(L4::Icu::Rights, l4_umword_t)
  { return -L4_ENOSYS; }
 
  int op_unmask(L4::Icu::Rights, l4_umword_t)
  { return -L4_ENOREPLY; }
 
  int op_set_mode(L4::Icu::Rights, l4_umword_t, l4_umword_t)
  { return -L4_ENOSYS; }
 
  void reset_queue_config(unsigned idx, unsigned num_max,
                          bool inc_generation = false)
  {
    _device_config->reset_queue(idx, num_max, inc_generation);
  }
 
  void init_mem_info(unsigned num)
  {
    _mem_info.init(num);
  }
 
  void device_error()
  {
    reset();
    _device_config->set_device_needs_reset();
 
    // the device MUST NOT notify the driver before DRIVER_OK.
    if (_device_config->status().driver_ok())
      {
        // we do not care about this anywhere, so skip
        // _dev_config->irq_status |= 1;
        trigger_driver_config_irq();
      }
  }
 
  bool setup_queue(Virtqueue *q, unsigned qn, unsigned num_max)
  {
    l4virtio_config_queue_t volatile const *qc;
    qc = _device_config->qconfig(qn);
    if (L4_UNLIKELY(qc == 0))
      return false;
 
    if (!qc->ready)
      {
        q->disable();
        return true;
      }
 
    // read to local variables before check
    l4_uint32_t num   = qc->num;
    l4_uint64_t desc  = qc->desc_addr;
    l4_uint64_t avail = qc->avail_addr;
    l4_uint64_t used  = qc->used_addr;
 
    if (0)
      printf("%p: setup queue: num=0x%x max_num=0x%x desc=0x%llx avail=0x%llx used=0x%llx\n",
             this, num, num_max, desc, avail, used);
 
    if (!num || num > num_max)
      return false;
 
    // num must be power of two
    if (num & (num - 1))
      return false;
 
    if (desc & 0xf)
      return false;
 
    if (avail & 0x1)
      return false;
 
    if (used & 0x3)
      return false;
 
    auto const *desc_info = _mem_info.find(desc, Virtqueue::desc_size(num));
    if (L4_UNLIKELY(!desc_info))
      return false;
 
    auto const *avail_info = _mem_info.find(avail, Virtqueue::avail_size(num));
    if (L4_UNLIKELY(!avail_info))
      return false;
 
    auto const *used_info = _mem_info.find(used, Virtqueue::used_size(num));
    if (L4_UNLIKELY(!used_info || !used_info->is_writable()))
      return false;
 
    L4Re::Util::Dbg()
      .printf("shm=[%llx-%llx] local=[%lx-%lx] desc=[%llx-%llx] (%p-%p)\n",
              desc_info->drv_base(), desc_info->drv_base() + desc_info->size() - 1,
              (unsigned long)desc_info->local_base(),
              (unsigned long)desc_info->local_base() + desc_info->size() - 1,
              desc, desc + Virtqueue::desc_size(num),
              desc_info->local(Ptr<char>(desc)),
              desc_info->local(Ptr<char>(desc)) + Virtqueue::desc_size(num));
 
    L4Re::Util::Dbg()
      .printf("shm=[%llx-%llx] local=[%lx-%lx] avail=[%llx-%llx] (%p-%p)\n",
              avail_info->drv_base(), avail_info->drv_base() + avail_info->size() - 1,
              (unsigned long)avail_info->local_base(),
              (unsigned long)avail_info->local_base() + avail_info->size() - 1,
              avail, avail + Virtqueue::avail_size(num),
              avail_info->local(Ptr<char>(avail)),
              avail_info->local(Ptr<char>(avail)) + Virtqueue::avail_size(num));
 
    L4Re::Util::Dbg()
      .printf("shm=[%llx-%llx] local=[%lx-%lx] used=[%llx-%llx] (%p-%p)\n",
              used_info->drv_base(), used_info->drv_base() + used_info->size() - 1,
              (unsigned long)used_info->local_base(),
              (unsigned long)used_info->local_base() + used_info->size() - 1,
              used, used + Virtqueue::used_size(num),
              used_info->local(Ptr<char>(used)),
              used_info->local(Ptr<char>(used)) + Virtqueue::used_size(num));
 
    q->setup(num, desc_info->local(Ptr<void>(desc)),
             avail_info->local(Ptr<void>(avail)),
             used_info->local(Ptr<void>(used)));
    return true;
  }
 
  void check_n_init_shm(L4Re::Util::Unique_cap<L4Re::Dataspace> &&shm,
                        l4_uint64_t base, l4_umword_t size, l4_addr_t offset)
  {
    if (_mem_info.full())
      L4Re::chksys(-L4_ENOMEM);
 
    auto const *i = _mem_info.add(base, size, offset, cxx::move(shm));
    L4Re::Util::Dbg()
      .printf("PORT[%p]: DMA guest [%llx-%llx]  local [%lx-%lx]  offset %lx\n",
              this, i->drv_base(), i->drv_base() + i->size() - 1,
              (unsigned long)i->local_base(),
              (unsigned long)i->local_base() + i->size() - 1,
              i->ds_offset());
  }
 
  bool handle_mem_cmd_write()
  {
    l4_uint32_t cmd = _device_config->get_cmd();
    if (L4_LIKELY(!(cmd & L4VIRTIO_CMD_MASK)))
      return false;
 
    switch (cmd & L4VIRTIO_CMD_MASK)
      {
      case L4VIRTIO_CMD_SET_STATUS:
        _set_status(cmd & ~L4VIRTIO_CMD_MASK);
        break;
 
      case L4VIRTIO_CMD_CFG_QUEUE:
        reconfig_queue(cmd & ~L4VIRTIO_CMD_MASK);
        break;
 
      default:
        // unknown command
        break;
      }
 
    _device_config->reset_cmd();
 
    return true;
  }
 
  void enable_trusted_ds_validation()
  {
    _trusted_ds_validation_enabled = true;
  }
 
  void
  add_trusted_dataspaces(std::shared_ptr<Ds_vector const> ds)
  {
    _trusted_ds_caps = ds;
  }
 
 
private:
  long validate_ds(L4::Cap<L4Re::Dataspace> ds)
  {
    if (!_trusted_ds_caps)
      return -L4_EINVAL;
    if (std::any_of(_trusted_ds_caps->cbegin(), _trusted_ds_caps->cend(),
                    [&ds](L4::Cap<L4Re::Dataspace> cap)
                      {
                        return L4Re::Env::env()->task()
                          ->cap_equal(ds, cap).label() == 1;
                      }
    ))
      {
        return L4_EOK;
      }
    return -L4_EINVAL;
  }
 
  void _check_n_init_shm(L4::Ipc::Snd_fpage shm_cap_fp,
                         l4_uint64_t base, l4_umword_t size, l4_addr_t offset)
  {
    if (!shm_cap_fp.cap_received())
      L4Re::chksys(-L4_EINVAL);
 
    L4Re::Util::Unique_cap<L4Re::Dataspace> ds(
        L4Re::chkcap(server_iface()->template rcv_cap<L4Re::Dataspace>(0)));
    L4Re::chksys(server_iface()->realloc_rcv_cap(0));
 
    if (_trusted_ds_validation_enabled)
      L4Re::chksys(validate_ds(ds.get()), "Validating the dataspace.");
 
    check_n_init_shm(cxx::move(ds), base, size, offset);
  }
 
  bool check_features_internal()
  {
    static_assert(sizeof(l4virtio_config_hdr_t::driver_features_map)
                    == sizeof(l4virtio_config_hdr_t::dev_features_map),
                  "Driver and device feature maps must be of the same size");
 
    // From the Virtio 1.0 specification 6.1 Driver Requirements and 6.2 Device
    // Requirements: A driver MUST accept VIRTIO_F_VERSION_1 if it is offered.
    // A device MUST offer VIRTIO_F_VERSION_1. A device MAY fail to operate
    // further if VIRTIO_F_VERSION_1 is not accepted.
    //
    // The L4virtio implementation does not support legacy interfaces so we
    // fail here if the Virtio 1.0 feature was not accepted.
    if (!_device_config->get_guest_feature(L4VIRTIO_FEATURE_VERSION_1))
      return false;
 
    for (auto i = 0u;
         i < sizeof(l4virtio_config_hdr_t::driver_features_map)
               / sizeof(l4virtio_config_hdr_t::driver_features_map[0]);
         i++)
      {
        // Driver must not accept features that were not offered by device
        if (_device_config->guest_features(i)
            & ~_device_config->host_features(i))
          return false;
      }
    return check_features();
  }
 
  void check_and_update_status(Dev_config::Status status)
  {
    // snapshot of current status
    Dev_config::Status current_status = _device_config->status();
 
    // handle reset
    if (!status.raw)
      {
        _device_config->set_status(status);
        return;
      }
 
    // Do no further processing in case of driver or device failure. If FAILED
    // or DEVICE_NEEDS_RESET are set only these fail_state bits will be set in
    // addition to the current status bits already set.
    if (current_status.fail_state() || status.fail_state())
      {
        if (current_status.fail_state() != status.fail_state())
          {
            current_status.fail_state() =
              current_status.fail_state() | status.fail_state();
            _device_config->set_status(current_status);
          }
        return;
      }
 
    // Enforce init sequence ACKNOWLEDGE, DRIVER, FEATURES_OK, DRIVER_OK.
    // We do not enforce that only one additional new bit is set per call.
    if ((!status.acked() && status.driver())
        || (!status.driver() && status.features_ok())
        || (!status.features_ok() && status.driver_ok()))
      {
        current_status.device_needs_reset() = 1;
        _device_config->set_status(current_status);
        return;
      }
 
    // only check feature compatibility before DRIVER_OK is set
    if (status.features_ok() && !status.driver_ok()
          && !check_features_internal())
      status.features_ok() = 0;
 
    // Note that if FEATURES_OK and DRIVER_OK are both updated to being set
    // at the same time the above check_features_internal() is skipped; this is
    // considered undefined behaviour but it is not prevented.
    if (status.running() && !check_queues())
      {
        current_status.device_needs_reset() = 1;
        _device_config->set_status(current_status);
        return;
      }
 
    _device_config->set_status(status);
  }
 
  int _set_status(unsigned new_status)
  {
    if (new_status == 0)
      {
        L4Re::Util::Dbg().printf("Resetting device\n");
        reset();
        _device_config->reset_hdr(true);
      }
 
    Dev_config::Status status(new_status);
    check_and_update_status(status);
 
    return 0;
  }
 
};
 
typedef Device_t<No_custom_data> Device;
 
} // namespace Svr
 
}