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![Michael S. Tsirkin](/assets/img/avatar_default.png)
We need a full barrier after writing out event index, using virt_store_mb there seems better than open-coding. As usual, we need a wrapper to account for strong barriers. It's tempting to use this in vhost as well, for that, we'll need a variant of smp_store_mb that works on __user pointers. Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
76 lines
1.8 KiB
C
76 lines
1.8 KiB
C
#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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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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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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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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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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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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