Merge tag 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost

Pull virtio/vhost updates from Michael Tsirkin:

 - new vsock device support in host and guest

 - platform IOMMU support in host and guest, including compatibility
   quirks for legacy systems.

 - misc fixes and cleanups.

* tag 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost:
  VSOCK: Use kvfree()
  vhost: split out vringh Kconfig
  vhost: detect 32 bit integer wrap around
  vhost: new device IOTLB API
  vhost: drop vringh dependency
  vhost: convert pre sorted vhost memory array to interval tree
  vhost: introduce vhost memory accessors
  VSOCK: Add Makefile and Kconfig
  VSOCK: Introduce vhost_vsock.ko
  VSOCK: Introduce virtio_transport.ko
  VSOCK: Introduce virtio_vsock_common.ko
  VSOCK: defer sock removal to transports
  VSOCK: transport-specific vsock_transport functions
  vhost: drop vringh dependency
  vop: pull in vhost Kconfig
  virtio: new feature to detect IOMMU device quirk
  balloon: check the number of available pages in leak balloon
  vhost: lockless enqueuing
  vhost: simplify work flushing

2 files changed, 16 insertions, 1 deletions

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 888d5f8322ce..4e7003db12c4 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -207,6 +207,8 @@ static unsigned leak_balloon(struct virtio_balloon *vb, size_t num)
         num = min(num, ARRAY_SIZE(vb->pfns));
 
         mutex_lock(&vb->balloon_lock);
+        /* We can't release more pages than taken */
+        num = min(num, (size_t)vb->num_pages);
         for (vb->num_pfns = 0; vb->num_pfns < num;
              vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
                 page = balloon_page_dequeue(vb_dev_info);
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index ca6bfddaacad..114a0c88afb8 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -117,7 +117,10 @@ struct vring_virtqueue {
 #define to_vvq(_vq) container_of(_vq, struct vring_virtqueue, vq)
 
 /*
- * The interaction between virtio and a possible IOMMU is a mess.
+ * Modern virtio devices have feature bits to specify whether they need a
+ * quirk and bypass the IOMMU. If not there, just use the DMA API.
+ *
+ * If there, the interaction between virtio and DMA API is messy.
  *
  * On most systems with virtio, physical addresses match bus addresses,
  * and it doesn't particularly matter whether we use the DMA API.
@@ -133,10 +136,18 @@ struct vring_virtqueue {
  *
  * For the time being, we preserve historic behavior and bypass the DMA
  * API.
+ *
+ * TODO: install a per-device DMA ops structure that does the right thing
+ * taking into account all the above quirks, and use the DMA API
+ * unconditionally on data path.
  */
 
 static bool vring_use_dma_api(struct virtio_device *vdev)
 {
+        if (!virtio_has_iommu_quirk(vdev))
+                return true;
+
+        /* Otherwise, we are left to guess. */
         /*
          * In theory, it's possible to have a buggy QEMU-supposed
          * emulated Q35 IOMMU and Xen enabled at the same time.  On
@@ -1099,6 +1110,8 @@ void vring_transport_features(struct virtio_device *vdev)
                         break;
                 case VIRTIO_F_VERSION_1:
                         break;
+                case VIRTIO_F_IOMMU_PLATFORM:
+                        break;
                 default:
                         /* We don't understand this bit. */
                         __virtio_clear_bit(vdev, i);