hw/virtio/vhost-backend.c

   1 /*
   2  * vhost-backend
   3  *
   4  * Copyright (c) 2013 Virtual Open Systems Sarl.
   5  *
   6  * This work is licensed under the terms of the GNU GPL, version 2 or later.
   7  * See the COPYING file in the top-level directory.
   8  *
   9  */
  10
  11 #include "hw/virtio/vhost.h"
  12 #include "hw/virtio/vhost-backend.h"
  13 #include "qemu/error-report.h"
  14 #include "linux/vhost.h"
  15
  16 #include <sys/ioctl.h>
  17
  18 static int vhost_kernel_call(struct vhost_dev *dev, unsigned long int request,
  19                              void *arg)
  20 {
  21     int fd = (uintptr_t) dev->opaque;
  22
  23     assert(dev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_KERNEL);
  24
  25     return ioctl(fd, request, arg);
  26 }
  27
  28 static int vhost_kernel_init(struct vhost_dev *dev, void *opaque)
  29 {
  30     assert(dev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_KERNEL);
  31
  32     dev->opaque = opaque;
  33
  34     return 0;
  35 }
  36
  37 static int vhost_kernel_cleanup(struct vhost_dev *dev)
  38 {
  39     int fd = (uintptr_t) dev->opaque;
  40
  41     assert(dev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_KERNEL);
  42
  43     return close(fd);
  44 }
  45
  46 static int vhost_kernel_get_vq_index(struct vhost_dev *dev, int idx)
  47 {
  48     assert(idx >= dev->vq_index && idx < dev->vq_index + dev->nvqs);
  49
  50     return idx - dev->vq_index;
  51 }
  52
  53 static int vhost_kernel_memslots_limit(struct vhost_dev *dev)
  54 {
  55     int limit = 64;
  56     char *s;
  57
  58     if (g_file_get_contents("/sys/module/vhost/parameters/max_mem_regions",
  59                             &s, NULL, NULL)) {
  60         uint64_t val = g_ascii_strtoull(s, NULL, 10);
  61         if (!((val == G_MAXUINT64 || !val) && errno)) {
  62             return val;
  63         }
  64         error_report("ignoring invalid max_mem_regions value in vhost module:"
  65                      " %s", s);
  66     }
  67     return limit;
  68 }
  69
  70 static int vhost_set_log_base(struct vhost_dev *dev, uint64_t base)
  71 {
  72     return vhost_kernel_call(dev, VHOST_SET_LOG_BASE, &base);
  73 }
  74
  75 static const VhostOps kernel_ops = {
  76         .backend_type = VHOST_BACKEND_TYPE_KERNEL,
  77         .vhost_call = vhost_kernel_call,
  78         .vhost_backend_init = vhost_kernel_init,
  79         .vhost_backend_cleanup = vhost_kernel_cleanup,
  80         .vhost_backend_get_vq_index = vhost_kernel_get_vq_index,
  81         .vhost_backend_memslots_limit = vhost_kernel_memslots_limit,
  82         .vhost_set_log_base = vhost_set_log_base,
  83 };
  84
  85 int vhost_set_backend_type(struct vhost_dev *dev, VhostBackendType backend_type)
  86 {
  87     int r = 0;
  88
  89     switch (backend_type) {
  90     case VHOST_BACKEND_TYPE_KERNEL:
  91         dev->vhost_ops = &kernel_ops;
  92         break;
  93     case VHOST_BACKEND_TYPE_USER:
  94         dev->vhost_ops = &user_ops;
  95         break;
  96     default:
  97         error_report("Unknown vhost backend type");
  98         r = -1;
  99     }
 100
 101     return r;
 102 }