1/* SPDX-License-Identifier: GPL-2.0 */ 2#ifndef _LINUX_VIRTIO_RING_H 3#define _LINUX_VIRTIO_RING_H 4 5#include <asm/barrier.h> 6#include <linux/irqreturn.h> 7#include <uapi/linux/virtio_ring.h> 8 9/* 10 * Barriers in virtio are tricky. Non-SMP virtio guests can't assume 11 * they're not on an SMP host system, so they need to assume real 12 * barriers. Non-SMP virtio hosts could skip the barriers, but does 13 * anyone care? 14 * 15 * For virtio_pci on SMP, we don't need to order with respect to MMIO 16 * accesses through relaxed memory I/O windows, so virt_mb() et al are 17 * sufficient. 18 * 19 * For using virtio to talk to real devices (eg. other heterogeneous 20 * CPUs) we do need real barriers. In theory, we could be using both 21 * kinds of virtio, so it's a runtime decision, and the branch is 22 * actually quite cheap. 23 */ 24 25static inline void virtio_mb(bool weak_barriers) 26{ 27 if (weak_barriers) 28 virt_mb(); 29 else 30 mb(); 31} 32 33static inline void virtio_rmb(bool weak_barriers) 34{ 35 if (weak_barriers) 36 virt_rmb(); 37 else 38 dma_rmb(); 39} 40 41static inline void virtio_wmb(bool weak_barriers) 42{ 43 if (weak_barriers) 44 virt_wmb(); 45 else 46 dma_wmb(); 47} 48 49#define virtio_store_mb(weak_barriers, p, v) \ 50do { \ 51 if (weak_barriers) { \ 52 virt_store_mb(*p, v); \ 53 } else { \ 54 WRITE_ONCE(*p, v); \ 55 mb(); \ 56 } \ 57} while (0) \ 58 59struct virtio_device; 60struct virtqueue; 61struct device; 62 63/* 64 * Creates a virtqueue and allocates the descriptor ring. If 65 * may_reduce_num is set, then this may allocate a smaller ring than 66 * expected. The caller should query virtqueue_get_vring_size to learn 67 * the actual size of the ring. 68 */ 69struct virtqueue *vring_create_virtqueue(unsigned int index, 70 unsigned int num, 71 unsigned int vring_align, 72 struct virtio_device *vdev, 73 bool weak_barriers, 74 bool may_reduce_num, 75 bool ctx, 76 bool (*notify)(struct virtqueue *vq), 77 void (*callback)(struct virtqueue *vq), 78 const char *name); 79 80/* 81 * Creates a virtqueue and allocates the descriptor ring with per 82 * virtqueue DMA device. 83 */ 84struct virtqueue *vring_create_virtqueue_dma(unsigned int index, 85 unsigned int num, 86 unsigned int vring_align, 87 struct virtio_device *vdev, 88 bool weak_barriers, 89 bool may_reduce_num, 90 bool ctx, 91 bool (*notify)(struct virtqueue *vq), 92 void (*callback)(struct virtqueue *vq), 93 const char *name, 94 struct device *dma_dev); 95 96/* 97 * Creates a virtqueue with a standard layout but a caller-allocated 98 * ring. 99 */ 100struct virtqueue *vring_new_virtqueue(unsigned int index, 101 unsigned int num, 102 unsigned int vring_align, 103 struct virtio_device *vdev, 104 bool weak_barriers, 105 bool ctx, 106 void *pages, 107 bool (*notify)(struct virtqueue *vq), 108 void (*callback)(struct virtqueue *vq), 109 const char *name); 110 111/* 112 * Destroys a virtqueue. If created with vring_create_virtqueue, this 113 * also frees the ring. 114 */ 115void vring_del_virtqueue(struct virtqueue *vq); 116 117/* Filter out transport-specific feature bits. */ 118void vring_transport_features(struct virtio_device *vdev); 119 120irqreturn_t vring_interrupt(int irq, void *_vq); 121 122u32 vring_notification_data(struct virtqueue *_vq); 123#endif /* _LINUX_VIRTIO_RING_H */ 124