cf94db2190
vring_create_virtqueue() allows the caller to specify via the
may_reduce_num parameter whether the vring code is allowed to
allocate a smaller ring than specified.
However, the split ring allocation code tries to allocate a
smaller ring on allocation failure regardless of what the
caller specified. This may cause trouble for e.g. virtio-pci
in legacy mode, which does not support ring resizing. (The
packed ring code does not resize in any case.)
Let's fix this by bailing out immediately in the split ring code
if the requested size cannot be allocated and may_reduce_num has
not been specified.
While at it, fix a typo in the usage instructions.
Fixes: 2a2d1382fe ("virtio: Add improved queue allocation API")
Cc: stable@vger.kernel.org # v4.6+
Signed-off-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Halil Pasic <pasic@linux.ibm.com>
Reviewed-by: Jens Freimann <jfreimann@redhat.com>
116 lines
3 KiB
C
116 lines
3 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_VIRTIO_RING_H
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#define _LINUX_VIRTIO_RING_H
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#include <asm/barrier.h>
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#include <linux/irqreturn.h>
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#include <uapi/linux/virtio_ring.h>
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/*
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* Barriers in virtio are tricky. Non-SMP virtio guests can't assume
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* they're not on an SMP host system, so they need to assume real
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* barriers. Non-SMP virtio hosts could skip the barriers, but does
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* anyone care?
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*
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* For virtio_pci on SMP, we don't need to order with respect to MMIO
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* accesses through relaxed memory I/O windows, so virt_mb() et al are
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* sufficient.
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*
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* For using virtio to talk to real devices (eg. other heterogeneous
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* CPUs) we do need real barriers. In theory, we could be using both
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* kinds of virtio, so it's a runtime decision, and the branch is
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* actually quite cheap.
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*/
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static inline void virtio_mb(bool weak_barriers)
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{
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if (weak_barriers)
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virt_mb();
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else
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mb();
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}
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static inline void virtio_rmb(bool weak_barriers)
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{
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if (weak_barriers)
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virt_rmb();
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else
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dma_rmb();
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}
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static inline void virtio_wmb(bool weak_barriers)
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{
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if (weak_barriers)
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virt_wmb();
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else
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dma_wmb();
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}
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static inline void virtio_store_mb(bool weak_barriers,
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__virtio16 *p, __virtio16 v)
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{
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if (weak_barriers) {
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virt_store_mb(*p, v);
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} else {
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WRITE_ONCE(*p, v);
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mb();
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}
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}
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struct virtio_device;
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struct virtqueue;
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/*
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* Creates a virtqueue and allocates the descriptor ring. If
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* may_reduce_num is set, then this may allocate a smaller ring than
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* expected. The caller should query virtqueue_get_vring_size to learn
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* the actual size of the ring.
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*/
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struct virtqueue *vring_create_virtqueue(unsigned int index,
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unsigned int num,
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unsigned int vring_align,
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struct virtio_device *vdev,
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bool weak_barriers,
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bool may_reduce_num,
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bool ctx,
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bool (*notify)(struct virtqueue *vq),
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void (*callback)(struct virtqueue *vq),
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const char *name);
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/* Creates a virtqueue with a custom layout. */
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struct virtqueue *__vring_new_virtqueue(unsigned int index,
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struct vring vring,
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struct virtio_device *vdev,
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bool weak_barriers,
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bool ctx,
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bool (*notify)(struct virtqueue *),
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void (*callback)(struct virtqueue *),
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const char *name);
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/*
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* Creates a virtqueue with a standard layout but a caller-allocated
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* ring.
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*/
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struct virtqueue *vring_new_virtqueue(unsigned int index,
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unsigned int num,
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unsigned int vring_align,
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struct virtio_device *vdev,
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bool weak_barriers,
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bool ctx,
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void *pages,
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bool (*notify)(struct virtqueue *vq),
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void (*callback)(struct virtqueue *vq),
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const char *name);
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/*
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* Destroys a virtqueue. If created with vring_create_virtqueue, this
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* also frees the ring.
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*/
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void vring_del_virtqueue(struct virtqueue *vq);
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/* Filter out transport-specific feature bits. */
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void vring_transport_features(struct virtio_device *vdev);
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irqreturn_t vring_interrupt(int irq, void *_vq);
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#endif /* _LINUX_VIRTIO_RING_H */
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