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 struct 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 */ 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 /* 81 * Creates a virtqueue and allocates the descriptor ring with per 82 * virtqueue DMA device. 83 */ 84 struct 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 */ 100 struct 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 */ 115 void vring_del_virtqueue(struct virtqueue *vq); 116 117 /* Filter out transport-specific feature bits. */ 118 void vring_transport_features(struct virtio_device *vdev); 119 120 irqreturn_t vring_interrupt(int irq, void *_vq); 121 122 u32 vring_notification_data(struct virtqueue *_vq); 123 #endif /* _LINUX_VIRTIO_RING_H */ 124
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