| /* Copyright 2012 Red Hat, Inc. |
| * Copyright IBM, Corp. 2012 |
| * |
| * Based on Linux 2.6.39 vhost code: |
| * Copyright (C) 2009 Red Hat, Inc. |
| * Copyright (C) 2006 Rusty Russell IBM Corporation |
| * |
| * Author: Michael S. Tsirkin <mst@redhat.com> |
| * Stefan Hajnoczi <stefanha@redhat.com> |
| * |
| * Inspiration, some code, and most witty comments come from |
| * Documentation/virtual/lguest/lguest.c, by Rusty Russell |
| * |
| * This work is licensed under the terms of the GNU GPL, version 2. |
| */ |
| |
| #include "trace.h" |
| #include "vring.h" |
| #include "qemu/error-report.h" |
| |
| /* Map the guest's vring to host memory */ |
| bool vring_setup(Vring *vring, VirtIODevice *vdev, int n) |
| { |
| hwaddr vring_addr = virtio_queue_get_ring_addr(vdev, n); |
| hwaddr vring_size = virtio_queue_get_ring_size(vdev, n); |
| void *vring_ptr; |
| |
| vring->broken = false; |
| |
| hostmem_init(&vring->hostmem); |
| vring_ptr = hostmem_lookup(&vring->hostmem, vring_addr, vring_size, true); |
| if (!vring_ptr) { |
| error_report("Failed to map vring " |
| "addr %#" HWADDR_PRIx " size %" HWADDR_PRIu, |
| vring_addr, vring_size); |
| vring->broken = true; |
| return false; |
| } |
| |
| vring_init(&vring->vr, virtio_queue_get_num(vdev, n), vring_ptr, 4096); |
| |
| vring->last_avail_idx = 0; |
| vring->last_used_idx = 0; |
| vring->signalled_used = 0; |
| vring->signalled_used_valid = false; |
| |
| trace_vring_setup(virtio_queue_get_ring_addr(vdev, n), |
| vring->vr.desc, vring->vr.avail, vring->vr.used); |
| return true; |
| } |
| |
| void vring_teardown(Vring *vring) |
| { |
| hostmem_finalize(&vring->hostmem); |
| } |
| |
| /* Disable guest->host notifies */ |
| void vring_disable_notification(VirtIODevice *vdev, Vring *vring) |
| { |
| if (!(vdev->guest_features & (1 << VIRTIO_RING_F_EVENT_IDX))) { |
| vring->vr.used->flags |= VRING_USED_F_NO_NOTIFY; |
| } |
| } |
| |
| /* Enable guest->host notifies |
| * |
| * Return true if the vring is empty, false if there are more requests. |
| */ |
| bool vring_enable_notification(VirtIODevice *vdev, Vring *vring) |
| { |
| if (vdev->guest_features & (1 << VIRTIO_RING_F_EVENT_IDX)) { |
| vring_avail_event(&vring->vr) = vring->vr.avail->idx; |
| } else { |
| vring->vr.used->flags &= ~VRING_USED_F_NO_NOTIFY; |
| } |
| smp_mb(); /* ensure update is seen before reading avail_idx */ |
| return !vring_more_avail(vring); |
| } |
| |
| /* This is stolen from linux/drivers/vhost/vhost.c:vhost_notify() */ |
| bool vring_should_notify(VirtIODevice *vdev, Vring *vring) |
| { |
| uint16_t old, new; |
| bool v; |
| /* Flush out used index updates. This is paired |
| * with the barrier that the Guest executes when enabling |
| * interrupts. */ |
| smp_mb(); |
| |
| if ((vdev->guest_features & VIRTIO_F_NOTIFY_ON_EMPTY) && |
| unlikely(vring->vr.avail->idx == vring->last_avail_idx)) { |
| return true; |
| } |
| |
| if (!(vdev->guest_features & VIRTIO_RING_F_EVENT_IDX)) { |
| return !(vring->vr.avail->flags & VRING_AVAIL_F_NO_INTERRUPT); |
| } |
| old = vring->signalled_used; |
| v = vring->signalled_used_valid; |
| new = vring->signalled_used = vring->last_used_idx; |
| vring->signalled_used_valid = true; |
| |
| if (unlikely(!v)) { |
| return true; |
| } |
| |
| return vring_need_event(vring_used_event(&vring->vr), new, old); |
| } |
| |
| /* This is stolen from linux/drivers/vhost/vhost.c. */ |
| static int get_indirect(Vring *vring, |
| struct iovec iov[], struct iovec *iov_end, |
| unsigned int *out_num, unsigned int *in_num, |
| struct vring_desc *indirect) |
| { |
| struct vring_desc desc; |
| unsigned int i = 0, count, found = 0; |
| |
| /* Sanity check */ |
| if (unlikely(indirect->len % sizeof(desc))) { |
| error_report("Invalid length in indirect descriptor: " |
| "len %#x not multiple of %#zx", |
| indirect->len, sizeof(desc)); |
| vring->broken = true; |
| return -EFAULT; |
| } |
| |
| count = indirect->len / sizeof(desc); |
| /* Buffers are chained via a 16 bit next field, so |
| * we can have at most 2^16 of these. */ |
| if (unlikely(count > USHRT_MAX + 1)) { |
| error_report("Indirect buffer length too big: %d", indirect->len); |
| vring->broken = true; |
| return -EFAULT; |
| } |
| |
| do { |
| struct vring_desc *desc_ptr; |
| |
| /* Translate indirect descriptor */ |
| desc_ptr = hostmem_lookup(&vring->hostmem, |
| indirect->addr + found * sizeof(desc), |
| sizeof(desc), false); |
| if (!desc_ptr) { |
| error_report("Failed to map indirect descriptor " |
| "addr %#" PRIx64 " len %zu", |
| (uint64_t)indirect->addr + found * sizeof(desc), |
| sizeof(desc)); |
| vring->broken = true; |
| return -EFAULT; |
| } |
| desc = *desc_ptr; |
| |
| /* Ensure descriptor has been loaded before accessing fields */ |
| barrier(); /* read_barrier_depends(); */ |
| |
| if (unlikely(++found > count)) { |
| error_report("Loop detected: last one at %u " |
| "indirect size %u", i, count); |
| vring->broken = true; |
| return -EFAULT; |
| } |
| |
| if (unlikely(desc.flags & VRING_DESC_F_INDIRECT)) { |
| error_report("Nested indirect descriptor"); |
| vring->broken = true; |
| return -EFAULT; |
| } |
| |
| /* Stop for now if there are not enough iovecs available. */ |
| if (iov >= iov_end) { |
| return -ENOBUFS; |
| } |
| |
| iov->iov_base = hostmem_lookup(&vring->hostmem, desc.addr, desc.len, |
| desc.flags & VRING_DESC_F_WRITE); |
| if (!iov->iov_base) { |
| error_report("Failed to map indirect descriptor" |
| "addr %#" PRIx64 " len %u", |
| (uint64_t)desc.addr, desc.len); |
| vring->broken = true; |
| return -EFAULT; |
| } |
| iov->iov_len = desc.len; |
| iov++; |
| |
| /* If this is an input descriptor, increment that count. */ |
| if (desc.flags & VRING_DESC_F_WRITE) { |
| *in_num += 1; |
| } else { |
| /* If it's an output descriptor, they're all supposed |
| * to come before any input descriptors. */ |
| if (unlikely(*in_num)) { |
| error_report("Indirect descriptor " |
| "has out after in: idx %u", i); |
| vring->broken = true; |
| return -EFAULT; |
| } |
| *out_num += 1; |
| } |
| i = desc.next; |
| } while (desc.flags & VRING_DESC_F_NEXT); |
| return 0; |
| } |
| |
| /* This looks in the virtqueue and for the first available buffer, and converts |
| * it to an iovec for convenient access. Since descriptors consist of some |
| * number of output then some number of input descriptors, it's actually two |
| * iovecs, but we pack them into one and note how many of each there were. |
| * |
| * This function returns the descriptor number found, or vq->num (which is |
| * never a valid descriptor number) if none was found. A negative code is |
| * returned on error. |
| * |
| * Stolen from linux/drivers/vhost/vhost.c. |
| */ |
| int vring_pop(VirtIODevice *vdev, Vring *vring, |
| struct iovec iov[], struct iovec *iov_end, |
| unsigned int *out_num, unsigned int *in_num) |
| { |
| struct vring_desc desc; |
| unsigned int i, head, found = 0, num = vring->vr.num; |
| uint16_t avail_idx, last_avail_idx; |
| |
| /* If there was a fatal error then refuse operation */ |
| if (vring->broken) { |
| return -EFAULT; |
| } |
| |
| /* Check it isn't doing very strange things with descriptor numbers. */ |
| last_avail_idx = vring->last_avail_idx; |
| avail_idx = vring->vr.avail->idx; |
| barrier(); /* load indices now and not again later */ |
| |
| if (unlikely((uint16_t)(avail_idx - last_avail_idx) > num)) { |
| error_report("Guest moved used index from %u to %u", |
| last_avail_idx, avail_idx); |
| vring->broken = true; |
| return -EFAULT; |
| } |
| |
| /* If there's nothing new since last we looked. */ |
| if (avail_idx == last_avail_idx) { |
| return -EAGAIN; |
| } |
| |
| /* Only get avail ring entries after they have been exposed by guest. */ |
| smp_rmb(); |
| |
| /* Grab the next descriptor number they're advertising, and increment |
| * the index we've seen. */ |
| head = vring->vr.avail->ring[last_avail_idx % num]; |
| |
| /* If their number is silly, that's an error. */ |
| if (unlikely(head >= num)) { |
| error_report("Guest says index %u > %u is available", head, num); |
| vring->broken = true; |
| return -EFAULT; |
| } |
| |
| if (vdev->guest_features & (1 << VIRTIO_RING_F_EVENT_IDX)) { |
| vring_avail_event(&vring->vr) = vring->vr.avail->idx; |
| } |
| |
| /* When we start there are none of either input nor output. */ |
| *out_num = *in_num = 0; |
| |
| i = head; |
| do { |
| if (unlikely(i >= num)) { |
| error_report("Desc index is %u > %u, head = %u", i, num, head); |
| vring->broken = true; |
| return -EFAULT; |
| } |
| if (unlikely(++found > num)) { |
| error_report("Loop detected: last one at %u vq size %u head %u", |
| i, num, head); |
| vring->broken = true; |
| return -EFAULT; |
| } |
| desc = vring->vr.desc[i]; |
| |
| /* Ensure descriptor is loaded before accessing fields */ |
| barrier(); |
| |
| if (desc.flags & VRING_DESC_F_INDIRECT) { |
| int ret = get_indirect(vring, iov, iov_end, out_num, in_num, &desc); |
| if (ret < 0) { |
| return ret; |
| } |
| continue; |
| } |
| |
| /* If there are not enough iovecs left, stop for now. The caller |
| * should check if there are more descs available once they have dealt |
| * with the current set. |
| */ |
| if (iov >= iov_end) { |
| return -ENOBUFS; |
| } |
| |
| /* TODO handle non-contiguous memory across region boundaries */ |
| iov->iov_base = hostmem_lookup(&vring->hostmem, desc.addr, desc.len, |
| desc.flags & VRING_DESC_F_WRITE); |
| if (!iov->iov_base) { |
| error_report("Failed to map vring desc addr %#" PRIx64 " len %u", |
| (uint64_t)desc.addr, desc.len); |
| vring->broken = true; |
| return -EFAULT; |
| } |
| iov->iov_len = desc.len; |
| iov++; |
| |
| if (desc.flags & VRING_DESC_F_WRITE) { |
| /* If this is an input descriptor, |
| * increment that count. */ |
| *in_num += 1; |
| } else { |
| /* If it's an output descriptor, they're all supposed |
| * to come before any input descriptors. */ |
| if (unlikely(*in_num)) { |
| error_report("Descriptor has out after in: idx %d", i); |
| vring->broken = true; |
| return -EFAULT; |
| } |
| *out_num += 1; |
| } |
| i = desc.next; |
| } while (desc.flags & VRING_DESC_F_NEXT); |
| |
| /* On success, increment avail index. */ |
| vring->last_avail_idx++; |
| return head; |
| } |
| |
| /* After we've used one of their buffers, we tell them about it. |
| * |
| * Stolen from linux/drivers/vhost/vhost.c. |
| */ |
| void vring_push(Vring *vring, unsigned int head, int len) |
| { |
| struct vring_used_elem *used; |
| uint16_t new; |
| |
| /* Don't touch vring if a fatal error occurred */ |
| if (vring->broken) { |
| return; |
| } |
| |
| /* The virtqueue contains a ring of used buffers. Get a pointer to the |
| * next entry in that used ring. */ |
| used = &vring->vr.used->ring[vring->last_used_idx % vring->vr.num]; |
| used->id = head; |
| used->len = len; |
| |
| /* Make sure buffer is written before we update index. */ |
| smp_wmb(); |
| |
| new = vring->vr.used->idx = ++vring->last_used_idx; |
| if (unlikely((int16_t)(new - vring->signalled_used) < (uint16_t)1)) { |
| vring->signalled_used_valid = false; |
| } |
| } |
