55e49dc43a
virtio is using barriers to order memory accesses, thus dma_wmb/rmb is a good match. Before [mst@tuck linux]$ size drivers/virtio/virtio_ring.o text data bss dec hex filename 11392 820 0 12212 2fb4 drivers/virtio/virtio_ring.o After mst@tuck linux]$ size drivers/virtio/virtio_ring.o text data bss dec hex filename 11284 820 0 12104 2f48 drivers/virtio/virtio_ring.o Cc: Ohad Ben-Cohen <ohad@wizery.com> Cc: Bjorn Andersson <bjorn.andersson@linaro.org> Cc: linux-remoteproc@vger.kernel.org Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
115 lines
3 KiB
C
115 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_ring_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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