text: /*
   * Virtio driver bits
   *
   * Copyright (c) 2013 Alexander Graf <agraf@suse.de>
   *
   * This work is licensed under the terms of the GNU GPL, version 2 or (at
   * your option) any later version. See the COPYING file in the top-level
   * directory.
   */
  
  #include "libc.h"
  #include "s390-ccw.h"
  #include "virtio.h"
  #include "virtio-scsi.h"
  #include "bswap.h"
  
  #define VRING_WAIT_REPLY_TIMEOUT 30
  
  static VRing block[VIRTIO_MAX_VQS];
  static char ring_area[VIRTIO_RING_SIZE * VIRTIO_MAX_VQS]
                       __attribute__((__aligned__(PAGE_SIZE)));
  
  static char chsc_page[PAGE_SIZE] __attribute__((__aligned__(PAGE_SIZE)));
  
  static VDev vdev = {
      .nr_vqs = 1,
      .vrings = block,
      .cmd_vr_idx = 0,
      .ring_area = ring_area,
      .wait_reply_timeout = VRING_WAIT_REPLY_TIMEOUT,
      .schid = { .one = 1 },
      .scsi_block_size = VIRTIO_SCSI_BLOCK_SIZE,
      .blk_factor = 1,
  };
  
  VDev *virtio_get_device(void)
  {
      return &vdev;
  }
  
  VirtioDevType virtio_get_device_type(void)
  {
      return vdev.senseid.cu_model;
  }
  
  /* virtio spec v1.0 para 4.3.3.2 */
  static long kvm_hypercall(unsigned long nr, unsigned long param1,
                            unsigned long param2, unsigned long param3)
  {
      register ulong r_nr asm("1") = nr;
      register ulong r_param1 asm("2") = param1;
      register ulong r_param2 asm("3") = param2;
      register ulong r_param3 asm("4") = param3;
      register long retval asm("2");
  
      asm volatile ("diag 2,4,0x500"
                    : "=d" (retval)
                    : "d" (r_nr), "0" (r_param1), "r"(r_param2), "d"(r_param3)
                    : "memory", "cc");
  
      return retval;
  }
  
  static long virtio_notify(SubChannelId schid, int vq_idx, long cookie)
  {
      return kvm_hypercall(KVM_S390_VIRTIO_CCW_NOTIFY, *(u32 *)&schid,
                           vq_idx, cookie);
  }
  
  /***********************************************
   *             Virtio functions                *
   ***********************************************/
  
  int drain_irqs(SubChannelId schid)
  {
      Irb irb = {};
      int r = 0;
  
      while (1) {
          /* FIXME: make use of TPI, for that enable subchannel and isc */
          if (tsch(schid, &irb)) {
              /* Might want to differentiate error codes later on. */
              if (irb.scsw.cstat) {
                  r = -EIO;
              } else if (irb.scsw.dstat != 0xc) {
                  r = -EIO;
              }
              return r;
          }
      }
  }
  
  static int run_ccw(VDev *vdev, int cmd, void *ptr, int len)
  {
      Ccw1 ccw = {};
      CmdOrb orb = {};
      Schib schib;
      int r;
  
      /* start command processing */
      stsch_err(vdev->schid, &schib);
      /* enable the subchannel for IPL device */
      schib.pmcw.ena = 1;
      msch(vdev->schid, &schib);
  
      /* start subchannel command */
      orb.fmt = 1;
      orb.cpa = (u32)(long)&ccw;
      orb.lpm = 0x80;
  
      ccw.cmd_code = cmd;
      ccw.cda = (long)ptr;
      ccw.count = len;
  
      r = ssch(vdev->schid, &orb);
      /*
       * XXX Wait until device is done processing the CCW. For now we can
       *     assume that a simple tsch will have finished the CCW processing,
       *     but the architecture allows for asynchronous operation
       */
      if (!r) {
          r = drain_irqs(vdev->schid);
      }
      return r;
  }
  
  static void vring_init(VRing *vr, VqInfo *info)
  {
      void *p = (void *) info->queue;
  
      debug_print_addr("init p", p);
      vr->id = info->index;
      vr->num = info->num;
      vr->desc = p;
      vr->avail = p + info->num * sizeof(VRingDesc);
      vr->used = (void *)(((unsigned long)&vr->avail->ring[info->num]
                 + info->align - 1) & ~(info->align - 1));
  
      /* Zero out all relevant field */
      vr->avail->flags = 0;
      vr->avail->idx = 0;
  
      /* We're running with interrupts off anyways, so don't bother */
      vr->used->flags = VRING_USED_F_NO_NOTIFY;
      vr->used->idx = 0;
      vr->used_idx = 0;
      vr->next_idx = 0;
      vr->cookie = 0;
  
      debug_print_addr("init vr", vr);
  }
  
  bool vring_notify(VRing *vr)
  {
      vr->cookie = virtio_notify(vr->schid, vr->id, vr->cookie);
      return vr->cookie >= 0;
  }
  
  void vring_send_buf(VRing *vr, void *p, int len, int flags)
  {
      /* For follow-up chains we need to keep the first entry point */
      if (!(flags & VRING_HIDDEN_IS_CHAIN)) {
          vr->avail->ring[vr->avail->idx % vr->num] = vr->next_idx;
      }
  
      vr->desc[vr->next_idx].addr = (ulong)p;
      vr->desc[vr->next_idx].len = len;
      vr->desc[vr->next_idx].flags = flags & ~VRING_HIDDEN_IS_CHAIN;
      vr->desc[vr->next_idx].next = vr->next_idx;
      vr->desc[vr->next_idx].next++;
      vr->next_idx++;
  
      /* Chains only have a single ID */
      if (!(flags & VRING_DESC_F_NEXT)) {
          vr->avail->idx++;
      }
  }
  
  u64 get_clock(void)
  {
      u64 r;
  
      asm volatile("stck %0" : "=Q" (r) : : "cc");
      return r;
  }
  
  ulong get_second(void)
  {
      return (get_clock() >> 12) / 1000000;
  }
  
  int vr_poll(VRing *vr)
  {
      if (vr->used->idx == vr->used_idx) {
          vring_notify(vr);
          yield();
          return 0;
      }
  
      vr->used_idx = vr->used->idx;
      vr->next_idx = 0;
      vr->desc[0].len = 0;
      vr->desc[0].flags = 0;
      return 1; /* vr has been updated */
  }
  
  /*
   * Wait for the host to reply.
   *
   * timeout is in seconds if > 0.
   *
   * Returns 0 on success, 1 on timeout.
   */
  int vring_wait_reply(void)
  {
      ulong target_second = get_second() + vdev.wait_reply_timeout;
  
      /* Wait for any queue to be updated by the host */
      do {
          int i, r = 0;
  
          for (i = 0; i < vdev.nr_vqs; i++) {
              r += vr_poll(&vdev.vrings[i]);
          }
          yield();
          if (r) {
              return 0;
          }
      } while (!vdev.wait_reply_timeout || (get_second() < target_second));
  
      return 1;
  }
  
  int virtio_run(VDev *vdev, int vqid, VirtioCmd *cmd)
  {
      VRing *vr = &vdev->vrings[vqid];
      int i = 0;
  
      do {
          vring_send_buf(vr, cmd[i].data, cmd[i].size,
                         cmd[i].flags | (i ? VRING_HIDDEN_IS_CHAIN : 0));
      } while (cmd[i++].flags & VRING_DESC_F_NEXT);
  
      vring_wait_reply();
      if (drain_irqs(vr->schid)) {
          return -1;
      }
      return 0;
  }
  
  void virtio_setup_ccw(VDev *vdev)
  {
      int i, rc, cfg_size = 0;
      unsigned char status = VIRTIO_CONFIG_S_DRIVER_OK;
      struct VirtioFeatureDesc {
          uint32_t features;
          uint8_t index;
      } __attribute__((packed)) feats;
  
      IPL_assert(virtio_is_supported(vdev->schid), "PE");
      /* device ID has been established now */
  
      vdev->config.blk.blk_size = 0; /* mark "illegal" - setup started... */
      vdev->guessed_disk_nature = VIRTIO_GDN_NONE;
  
      run_ccw(vdev, CCW_CMD_VDEV_RESET, NULL, 0);
  
      switch (vdev->senseid.cu_model) {
      case VIRTIO_ID_NET:
          vdev->nr_vqs = 2;
          vdev->cmd_vr_idx = 0;
          cfg_size = sizeof(vdev->config.net);
          break;
      case VIRTIO_ID_BLOCK:
          vdev->nr_vqs = 1;
          vdev->cmd_vr_idx = 0;
          cfg_size = sizeof(vdev->config.blk);
          break;
      case VIRTIO_ID_SCSI:
          vdev->nr_vqs = 3;
          vdev->cmd_vr_idx = VR_REQUEST;
          cfg_size = sizeof(vdev->config.scsi);
          break;
      default:
          panic("Unsupported virtio device\n");
      }
      IPL_assert(run_ccw(vdev, CCW_CMD_READ_CONF, &vdev->config, cfg_size) == 0,
                 "Could not get block device configuration");
  
      /* Feature negotiation */
      for (i = 0; i < ARRAY_SIZE(vdev->guest_features); i++) {
          feats.features = 0;
          feats.index = i;
          rc = run_ccw(vdev, CCW_CMD_READ_FEAT, &feats, sizeof(feats));
          IPL_assert(rc == 0, "Could not get features bits");
          vdev->guest_features[i] &= bswap32(feats.features);
          feats.features = bswap32(vdev->guest_features[i]);
          rc = run_ccw(vdev, CCW_CMD_WRITE_FEAT, &feats, sizeof(feats));
          IPL_assert(rc == 0, "Could not set features bits");
      }
  
      for (i = 0; i < vdev->nr_vqs; i++) {
          VqInfo info = {
              .queue = (unsigned long long) ring_area + (i * VIRTIO_RING_SIZE),
              .align = KVM_S390_VIRTIO_RING_ALIGN,
              .index = i,
              .num = 0,
          };
          VqConfig config = {
              .index = i,
              .num = 0,
          };
  
          IPL_assert(
              run_ccw(vdev, CCW_CMD_READ_VQ_CONF, &config, sizeof(config)) == 0,
              "Could not get block device VQ configuration");
          info.num = config.num;
          vring_init(&vdev->vrings[i], &info);
          vdev->vrings[i].schid = vdev->schid;
          IPL_assert(run_ccw(vdev, CCW_CMD_SET_VQ, &info, sizeof(info)) == 0,
                     "Cannot set VQ info");
      }
      IPL_assert(
          run_ccw(vdev, CCW_CMD_WRITE_STATUS, &status, sizeof(status)) == 0,
          "Could not write status to host");
  }
  
  bool virtio_is_supported(SubChannelId schid)
  {
      vdev.schid = schid;
      memset(&vdev.senseid, 0, sizeof(vdev.senseid));
      /* run sense id command */
      if (run_ccw(&vdev, CCW_CMD_SENSE_ID, &vdev.senseid, sizeof(vdev.senseid))) {
          return false;
      }
      if (vdev.senseid.cu_type == 0x3832) {
          switch (vdev.senseid.cu_model) {
          case VIRTIO_ID_BLOCK:
          case VIRTIO_ID_SCSI:
          case VIRTIO_ID_NET:
              return true;
          }
      }
      return false;
  }
  
  int enable_mss_facility(void)
  {
      int ret;
      ChscAreaSda *sda_area = (ChscAreaSda *) chsc_page;
  
      memset(sda_area, 0, PAGE_SIZE);
      sda_area->request.length = 0x0400;
      sda_area->request.code = 0x0031;
      sda_area->operation_code = 0x2;
  
      ret = chsc(sda_area);
      if ((ret == 0) && (sda_area->response.code == 0x0001)) {
          return 0;
      }
      return -EIO;
  }
  