diff options
Diffstat (limited to 'hw/virtio/dataplane/vring.c')
| -rw-r--r-- | hw/virtio/dataplane/vring.c | 363 |
1 files changed, 363 insertions, 0 deletions
diff --git a/hw/virtio/dataplane/vring.c b/hw/virtio/dataplane/vring.c new file mode 100644 index 0000000000..e0d6e83625 --- /dev/null +++ b/hw/virtio/dataplane/vring.c @@ -0,0 +1,363 @@ +/* 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 "hw/virtio/dataplane/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; + } +} |