1 files changed, 35 insertions, 13 deletions

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 096b857e7b75..ee663c458b20 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -80,6 +80,12 @@ struct vring_virtqueue {
         /* Last used index we've seen. */
         u16 last_used_idx;
 
+        /* Last written value to avail->flags */
+        u16 avail_flags_shadow;
+
+        /* Last written value to avail->idx in guest byte order */
+        u16 avail_idx_shadow;
+
         /* How to notify other side. FIXME: commonalize hcalls! */
         bool (*notify)(struct virtqueue *vq);
 
@@ -109,7 +115,7 @@ static struct vring_desc *alloc_indirect(struct virtqueue *_vq,
          * otherwise virt_to_phys will give us bogus addresses in the
          * virtqueue.
          */
-        gfp &= ~(__GFP_HIGHMEM | __GFP_HIGH);
+        gfp &= ~__GFP_HIGHMEM;
 
         desc = kmalloc(total_sg * sizeof(struct vring_desc), gfp);
         if (!desc)
@@ -235,13 +241,14 @@ static inline int virtqueue_add(struct virtqueue *_vq,
 
         /* Put entry in available array (but don't update avail->idx until they
          * do sync). */
-        avail = virtio16_to_cpu(_vq->vdev, vq->vring.avail->idx) & (vq->vring.num - 1);
+        avail = vq->avail_idx_shadow & (vq->vring.num - 1);
         vq->vring.avail->ring[avail] = cpu_to_virtio16(_vq->vdev, head);
 
         /* Descriptors and available array need to be set before we expose the
          * new available array entries. */
         virtio_wmb(vq->weak_barriers);
-        vq->vring.avail->idx = cpu_to_virtio16(_vq->vdev, virtio16_to_cpu(_vq->vdev, vq->vring.avail->idx) + 1);
+        vq->avail_idx_shadow++;
+        vq->vring.avail->idx = cpu_to_virtio16(_vq->vdev, vq->avail_idx_shadow);
         vq->num_added++;
 
         pr_debug("Added buffer head %i to %p\n", head, vq);
@@ -354,8 +361,8 @@ bool virtqueue_kick_prepare(struct virtqueue *_vq)
          * event. */
         virtio_mb(vq->weak_barriers);
 
-        old = virtio16_to_cpu(_vq->vdev, vq->vring.avail->idx) - vq->num_added;
-        new = virtio16_to_cpu(_vq->vdev, vq->vring.avail->idx);
+        old = vq->avail_idx_shadow - vq->num_added;
+        new = vq->avail_idx_shadow;
         vq->num_added = 0;
 
 #ifdef DEBUG
@@ -510,7 +517,7 @@ void *virtqueue_get_buf(struct virtqueue *_vq, unsigned int *len)
         /* If we expect an interrupt for the next entry, tell host
          * by writing event index and flush out the write before
          * the read in the next get_buf call. */
-        if (!(vq->vring.avail->flags & cpu_to_virtio16(_vq->vdev, VRING_AVAIL_F_NO_INTERRUPT))) {
+        if (!(vq->avail_flags_shadow & VRING_AVAIL_F_NO_INTERRUPT)) {
                 vring_used_event(&vq->vring) = cpu_to_virtio16(_vq->vdev, vq->last_used_idx);
                 virtio_mb(vq->weak_barriers);
         }
@@ -537,7 +544,11 @@ void virtqueue_disable_cb(struct virtqueue *_vq)
 {
         struct vring_virtqueue *vq = to_vvq(_vq);
 
-        vq->vring.avail->flags |= cpu_to_virtio16(_vq->vdev, VRING_AVAIL_F_NO_INTERRUPT);
+        if (!(vq->avail_flags_shadow & VRING_AVAIL_F_NO_INTERRUPT)) {
+                vq->avail_flags_shadow |= VRING_AVAIL_F_NO_INTERRUPT;
+                vq->vring.avail->flags = cpu_to_virtio16(_vq->vdev, vq->avail_flags_shadow);
+        }
+
 }
 EXPORT_SYMBOL_GPL(virtqueue_disable_cb);
 
@@ -565,7 +576,10 @@ unsigned virtqueue_enable_cb_prepare(struct virtqueue *_vq)
         /* Depending on the VIRTIO_RING_F_EVENT_IDX feature, we need to
          * either clear the flags bit or point the event index at the next
          * entry. Always do both to keep code simple. */
-        vq->vring.avail->flags &= cpu_to_virtio16(_vq->vdev, ~VRING_AVAIL_F_NO_INTERRUPT);
+        if (vq->avail_flags_shadow & VRING_AVAIL_F_NO_INTERRUPT) {
+                vq->avail_flags_shadow &= ~VRING_AVAIL_F_NO_INTERRUPT;
+                vq->vring.avail->flags = cpu_to_virtio16(_vq->vdev, vq->avail_flags_shadow);
+        }
         vring_used_event(&vq->vring) = cpu_to_virtio16(_vq->vdev, last_used_idx = vq->last_used_idx);
         END_USE(vq);
         return last_used_idx;
@@ -633,9 +647,12 @@ bool virtqueue_enable_cb_delayed(struct virtqueue *_vq)
         /* Depending on the VIRTIO_RING_F_USED_EVENT_IDX feature, we need to
          * either clear the flags bit or point the event index at the next
          * entry. Always do both to keep code simple. */
-        vq->vring.avail->flags &= cpu_to_virtio16(_vq->vdev, ~VRING_AVAIL_F_NO_INTERRUPT);
+        if (vq->avail_flags_shadow & VRING_AVAIL_F_NO_INTERRUPT) {
+                vq->avail_flags_shadow &= ~VRING_AVAIL_F_NO_INTERRUPT;
+                vq->vring.avail->flags = cpu_to_virtio16(_vq->vdev, vq->avail_flags_shadow);
+        }
         /* TODO: tune this threshold */
-        bufs = (u16)(virtio16_to_cpu(_vq->vdev, vq->vring.avail->idx) - vq->last_used_idx) * 3 / 4;
+        bufs = (u16)(vq->avail_idx_shadow - vq->last_used_idx) * 3 / 4;
         vring_used_event(&vq->vring) = cpu_to_virtio16(_vq->vdev, vq->last_used_idx + bufs);
         virtio_mb(vq->weak_barriers);
         if (unlikely((u16)(virtio16_to_cpu(_vq->vdev, vq->vring.used->idx) - vq->last_used_idx) > bufs)) {
@@ -670,7 +687,8 @@ void *virtqueue_detach_unused_buf(struct virtqueue *_vq)
                 /* detach_buf clears data, so grab it now. */
                 buf = vq->data[i];
                 detach_buf(vq, i);
-                vq->vring.avail->idx = cpu_to_virtio16(_vq->vdev, virtio16_to_cpu(_vq->vdev, vq->vring.avail->idx) - 1);
+                vq->avail_idx_shadow--;
+                vq->vring.avail->idx = cpu_to_virtio16(_vq->vdev, vq->avail_idx_shadow);
                 END_USE(vq);
                 return buf;
         }
@@ -735,6 +753,8 @@ struct virtqueue *vring_new_virtqueue(unsigned int index,
         vq->weak_barriers = weak_barriers;
         vq->broken = false;
         vq->last_used_idx = 0;
+        vq->avail_flags_shadow = 0;
+        vq->avail_idx_shadow = 0;
         vq->num_added = 0;
         list_add_tail(&vq->vq.list, &vdev->vqs);
 #ifdef DEBUG
@@ -746,8 +766,10 @@ struct virtqueue *vring_new_virtqueue(unsigned int index,
         vq->event = virtio_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX);
 
         /* No callback?  Tell other side not to bother us. */
-        if (!callback)
-                vq->vring.avail->flags |= cpu_to_virtio16(vdev, VRING_AVAIL_F_NO_INTERRUPT);
+        if (!callback) {
+                vq->avail_flags_shadow |= VRING_AVAIL_F_NO_INTERRUPT;
+                vq->vring.avail->flags = cpu_to_virtio16(vdev, vq->avail_flags_shadow);
+        }
 
         /* Put everything in free lists. */
         vq->free_head = 0;