1 #ifndef _LINUX_VIRTIO_RING_H 2 #define _LINUX_VIRTIO_RING_H 3 4 #include <linux/irqreturn.h> 5 #include <uapi/linux/virtio_ring.h> 6 7 /* 8 * Barriers in virtio are tricky. Non-SMP virtio guests can't assume 9 * they're not on an SMP host system, so they need to assume real 10 * barriers. Non-SMP virtio hosts could skip the barriers, but does 11 * anyone care? 12 * 13 * For virtio_pci on SMP, we don't need to order with respect to MMIO 14 * accesses through relaxed memory I/O windows, so smp_mb() et al are 15 * sufficient. 16 * 17 * For using virtio to talk to real devices (eg. other heterogeneous 18 * CPUs) we do need real barriers. In theory, we could be using both 19 * kinds of virtio, so it's a runtime decision, and the branch is 20 * actually quite cheap. 21 */ 22 23 #ifdef CONFIG_SMP 24 static inline void virtio_mb(bool weak_barriers) 25 { 26 if (weak_barriers) 27 smp_mb(); 28 else 29 mb(); 30 } 31 32 static inline void virtio_rmb(bool weak_barriers) 33 { 34 if (weak_barriers) 35 smp_rmb(); 36 else 37 rmb(); 38 } 39 40 static inline void virtio_wmb(bool weak_barriers) 41 { 42 if (weak_barriers) 43 smp_wmb(); 44 else 45 wmb(); 46 } 47 #else 48 static inline void virtio_mb(bool weak_barriers) 49 { 50 mb(); 51 } 52 53 static inline void virtio_rmb(bool weak_barriers) 54 { 55 rmb(); 56 } 57 58 static inline void virtio_wmb(bool weak_barriers) 59 { 60 wmb(); 61 } 62 #endif 63 64 struct virtio_device; 65 struct virtqueue; 66 67 struct virtqueue *vring_new_virtqueue(unsigned int index, 68 unsigned int num, 69 unsigned int vring_align, 70 struct virtio_device *vdev, 71 bool weak_barriers, 72 void *pages, 73 void (*notify)(struct virtqueue *vq), 74 void (*callback)(struct virtqueue *vq), 75 const char *name); 76 void vring_del_virtqueue(struct virtqueue *vq); 77 /* Filter out transport-specific feature bits. */ 78 void vring_transport_features(struct virtio_device *vdev); 79 80 irqreturn_t vring_interrupt(int irq, void *_vq); 81 #endif /* _LINUX_VIRTIO_RING_H */ 82