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 25 static inline void virtio_mb(bool weak_barriers) 26 { 27 if (weak_barriers) 28 virt_mb(); 29 else 30 mb(); 31 } 32 33 static inline void virtio_rmb(bool weak_barriers) 34 { 35 if (weak_barriers) 36 virt_rmb(); 37 else 38 dma_rmb(); 39 } 40 41 static 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) \ 50 do { \ 51 if (weak_barriers) { \ 52 virt_store_mb(*p, v); \ 53 } else { \ 54 WRITE_ONCE(*p, v); \ 55 mb(); \ 56 } \ 57 } while (0) \ 58 59 struct virtio_device; 60 struct virtqueue; 61 62 /* 63 * Creates a virtqueue and allocates the descriptor ring. If 64 * may_reduce_num is set, then this may allocate a smaller ring than 65 * expected. The caller should query virtqueue_get_vring_size to learn 66 * the actual size of the ring. 67 */ 68 struct virtqueue *vring_create_virtqueue(unsigned int index, 69 unsigned int num, 70 unsigned int vring_align, 71 struct virtio_device *vdev, 72 bool weak_barriers, 73 bool may_reduce_num, 74 bool ctx, 75 bool (*notify)(struct virtqueue *vq), 76 void (*callback)(struct virtqueue *vq), 77 const char *name); 78 79 /* Creates a virtqueue with a custom layout. */ 80 struct virtqueue *__vring_new_virtqueue(unsigned int index, 81 struct vring vring, 82 struct virtio_device *vdev, 83 bool weak_barriers, 84 bool ctx, 85 bool (*notify)(struct virtqueue *), 86 void (*callback)(struct virtqueue *), 87 const char *name); 88 89 /* 90 * Creates a virtqueue with a standard layout but a caller-allocated 91 * ring. 92 */ 93 struct virtqueue *vring_new_virtqueue(unsigned int index, 94 unsigned int num, 95 unsigned int vring_align, 96 struct virtio_device *vdev, 97 bool weak_barriers, 98 bool ctx, 99 void *pages, 100 bool (*notify)(struct virtqueue *vq), 101 void (*callback)(struct virtqueue *vq), 102 const char *name); 103 104 /* 105 * Destroys a virtqueue. If created with vring_create_virtqueue, this 106 * also frees the ring. 107 */ 108 void vring_del_virtqueue(struct virtqueue *vq); 109 110 /* Filter out transport-specific feature bits. */ 111 void vring_transport_features(struct virtio_device *vdev); 112 113 irqreturn_t vring_interrupt(int irq, void *_vq); 114 #endif /* _LINUX_VIRTIO_RING_H */ 115