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dataplane: endianness-aware accesses
The vring.c code currently assumes that guest and host endianness match, which is not true for a number of cases: - emulating targets with a different endianness than the host - bi-endian targets, where the correct endianness depends on the virtio device - upcoming support for the virtio-1 standard mandates little-endian accesses even for big-endian targets and hosts Make sure to use accessors that depend on the virtio device. Note that dataplane now needs to be built per-target. Cc: Stefan Hajnoczi <stefanha@redhat.com> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Fam Zheng <famz@redhat.com> Reviewed-by: David Gibson <david@gibson.dropbear.id.au> Tested-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Message-id: 1422289602-17874-2-git-send-email-cornelia.huck@de.ibm.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Cornelia Huck
Stefan Hajnoczi
parent
9a75b0a037
commit
b0e5d90ebc
7 changed files with 117 additions and 35 deletions
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@ -18,7 +18,9 @@
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#include "hw/hw.h"
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#include "exec/memory.h"
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#include "exec/address-spaces.h"
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#include "hw/virtio/virtio-access.h"
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#include "hw/virtio/dataplane/vring.h"
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#include "hw/virtio/dataplane/vring-accessors.h"
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#include "qemu/error-report.h"
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/* vring_map can be coupled with vring_unmap or (if you still have the
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@ -83,7 +85,7 @@ bool vring_setup(Vring *vring, VirtIODevice *vdev, int n)
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vring_init(&vring->vr, virtio_queue_get_num(vdev, n), vring_ptr, 4096);
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vring->last_avail_idx = virtio_queue_get_last_avail_idx(vdev, n);
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vring->last_used_idx = vring->vr.used->idx;
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vring->last_used_idx = vring_get_used_idx(vdev, vring);
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vring->signalled_used = 0;
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vring->signalled_used_valid = false;
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@ -104,7 +106,7 @@ void vring_teardown(Vring *vring, VirtIODevice *vdev, int n)
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void vring_disable_notification(VirtIODevice *vdev, Vring *vring)
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{
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if (!(vdev->guest_features & (1 << VIRTIO_RING_F_EVENT_IDX))) {
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vring->vr.used->flags |= VRING_USED_F_NO_NOTIFY;
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vring_set_used_flags(vdev, vring, VRING_USED_F_NO_NOTIFY);
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}
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}
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@ -117,10 +119,10 @@ bool vring_enable_notification(VirtIODevice *vdev, Vring *vring)
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if (vdev->guest_features & (1 << VIRTIO_RING_F_EVENT_IDX)) {
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vring_avail_event(&vring->vr) = vring->vr.avail->idx;
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} else {
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vring->vr.used->flags &= ~VRING_USED_F_NO_NOTIFY;
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vring_clear_used_flags(vdev, vring, VRING_USED_F_NO_NOTIFY);
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}
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smp_mb(); /* ensure update is seen before reading avail_idx */
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return !vring_more_avail(vring);
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return !vring_more_avail(vdev, vring);
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}
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/* This is stolen from linux/drivers/vhost/vhost.c:vhost_notify() */
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@ -134,12 +136,13 @@ bool vring_should_notify(VirtIODevice *vdev, Vring *vring)
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smp_mb();
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if ((vdev->guest_features & (1 << VIRTIO_F_NOTIFY_ON_EMPTY)) &&
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unlikely(vring->vr.avail->idx == vring->last_avail_idx)) {
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unlikely(!vring_more_avail(vdev, vring))) {
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return true;
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}
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if (!(vdev->guest_features & (1 << VIRTIO_RING_F_EVENT_IDX))) {
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return !(vring->vr.avail->flags & VRING_AVAIL_F_NO_INTERRUPT);
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return !(vring_get_avail_flags(vdev, vring) &
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VRING_AVAIL_F_NO_INTERRUPT);
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}
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old = vring->signalled_used;
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v = vring->signalled_used_valid;
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@ -202,9 +205,19 @@ static int get_desc(Vring *vring, VirtQueueElement *elem,
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return 0;
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}
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static void copy_in_vring_desc(VirtIODevice *vdev,
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const struct vring_desc *guest,
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struct vring_desc *host)
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{
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host->addr = virtio_ldq_p(vdev, &guest->addr);
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host->len = virtio_ldl_p(vdev, &guest->len);
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host->flags = virtio_lduw_p(vdev, &guest->flags);
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host->next = virtio_lduw_p(vdev, &guest->next);
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}
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/* This is stolen from linux/drivers/vhost/vhost.c. */
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static int get_indirect(Vring *vring, VirtQueueElement *elem,
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struct vring_desc *indirect)
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static int get_indirect(VirtIODevice *vdev, Vring *vring,
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VirtQueueElement *elem, struct vring_desc *indirect)
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{
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struct vring_desc desc;
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unsigned int i = 0, count, found = 0;
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@ -244,7 +257,7 @@ static int get_indirect(Vring *vring, VirtQueueElement *elem,
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vring->broken = true;
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return -EFAULT;
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}
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desc = *desc_ptr;
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copy_in_vring_desc(vdev, desc_ptr, &desc);
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memory_region_unref(mr);
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/* Ensure descriptor has been loaded before accessing fields */
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@ -320,7 +333,7 @@ int vring_pop(VirtIODevice *vdev, Vring *vring,
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/* Check it isn't doing very strange things with descriptor numbers. */
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last_avail_idx = vring->last_avail_idx;
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avail_idx = vring->vr.avail->idx;
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avail_idx = vring_get_avail_idx(vdev, vring);
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barrier(); /* load indices now and not again later */
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if (unlikely((uint16_t)(avail_idx - last_avail_idx) > num)) {
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@ -341,7 +354,7 @@ int vring_pop(VirtIODevice *vdev, Vring *vring,
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/* Grab the next descriptor number they're advertising, and increment
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* the index we've seen. */
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head = vring->vr.avail->ring[last_avail_idx % num];
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head = vring_get_avail_ring(vdev, vring, last_avail_idx % num);
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elem->index = head;
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@ -365,13 +378,13 @@ int vring_pop(VirtIODevice *vdev, Vring *vring,
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ret = -EFAULT;
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goto out;
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}
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desc = vring->vr.desc[i];
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copy_in_vring_desc(vdev, &vring->vr.desc[i], &desc);
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/* Ensure descriptor is loaded before accessing fields */
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barrier();
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if (desc.flags & VRING_DESC_F_INDIRECT) {
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ret = get_indirect(vring, elem, &desc);
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ret = get_indirect(vdev, vring, elem, &desc);
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if (ret < 0) {
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goto out;
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}
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@ -407,9 +420,9 @@ out:
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*
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* Stolen from linux/drivers/vhost/vhost.c.
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*/
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void vring_push(Vring *vring, VirtQueueElement *elem, int len)
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void vring_push(VirtIODevice *vdev, Vring *vring, VirtQueueElement *elem,
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int len)
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{
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struct vring_used_elem *used;
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unsigned int head = elem->index;
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uint16_t new;
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@ -422,14 +435,16 @@ void vring_push(Vring *vring, VirtQueueElement *elem, int len)
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/* The virtqueue contains a ring of used buffers. Get a pointer to the
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* next entry in that used ring. */
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used = &vring->vr.used->ring[vring->last_used_idx % vring->vr.num];
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used->id = head;
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used->len = len;
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vring_set_used_ring_id(vdev, vring, vring->last_used_idx % vring->vr.num,
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head);
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vring_set_used_ring_len(vdev, vring, vring->last_used_idx % vring->vr.num,
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len);
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/* Make sure buffer is written before we update index. */
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smp_wmb();
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new = vring->vr.used->idx = ++vring->last_used_idx;
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new = ++vring->last_used_idx;
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vring_set_used_idx(vdev, vring, new);
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if (unlikely((int16_t)(new - vring->signalled_used) < (uint16_t)1)) {
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vring->signalled_used_valid = false;
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}
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