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 static inline void virtio_store_mb(bool weak_barriers, 50 __virtio16 *p, __virtio16 v) 51 { 52 if (weak_barriers) { 53 virt_store_mb(*p, v); 54 } else { 55 WRITE_ONCE(*p, v); 56 mb(); 57 } 58 } 59 60 struct virtio_device; 61 struct virtqueue; 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 */ 69 struct 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 /* Creates a virtqueue with a custom layout. */ 81 struct virtqueue *__vring_new_virtqueue(unsigned int index, 82 struct vring vring, 83 struct virtio_device *vdev, 84 bool weak_barriers, 85 bool ctx, 86 bool (*notify)(struct virtqueue *), 87 void (*callback)(struct virtqueue *), 88 const char *name); 89 90 /* 91 * Creates a virtqueue with a standard layout but a caller-allocated 92 * ring. 93 */ 94 struct virtqueue *vring_new_virtqueue(unsigned int index, 95 unsigned int num, 96 unsigned int vring_align, 97 struct virtio_device *vdev, 98 bool weak_barriers, 99 bool ctx, 100 void *pages, 101 bool (*notify)(struct virtqueue *vq), 102 void (*callback)(struct virtqueue *vq), 103 const char *name); 104 105 /* 106 * Destroys a virtqueue. If created with vring_create_virtqueue, this 107 * also frees the ring. 108 */ 109 void vring_del_virtqueue(struct virtqueue *vq); 110 111 /* Filter out transport-specific feature bits. */ 112 void vring_transport_features(struct virtio_device *vdev); 113 114 irqreturn_t vring_interrupt(int irq, void *_vq); 115 #endif /* _LINUX_VIRTIO_RING_H */ 116