1 #ifndef _LINUX_VIRTIO_RING_H 2 #define _LINUX_VIRTIO_RING_H 3 4 #include <asm/barrier.h> 5 #include <linux/irqreturn.h> 6 #include <uapi/linux/virtio_ring.h> 7 8 /* 9 * Barriers in virtio are tricky. Non-SMP virtio guests can't assume 10 * they're not on an SMP host system, so they need to assume real 11 * barriers. Non-SMP virtio hosts could skip the barriers, but does 12 * anyone care? 13 * 14 * For virtio_pci on SMP, we don't need to order with respect to MMIO 15 * accesses through relaxed memory I/O windows, so smp_mb() et al are 16 * sufficient. 17 * 18 * For using virtio to talk to real devices (eg. other heterogeneous 19 * CPUs) we do need real barriers. In theory, we could be using both 20 * kinds of virtio, so it's a runtime decision, and the branch is 21 * actually quite cheap. 22 */ 23 24 #ifdef CONFIG_SMP 25 static inline void virtio_mb(bool weak_barriers) 26 { 27 if (weak_barriers) 28 smp_mb(); 29 else 30 mb(); 31 } 32 33 static inline void virtio_rmb(bool weak_barriers) 34 { 35 if (weak_barriers) 36 smp_rmb(); 37 else 38 rmb(); 39 } 40 41 static inline void virtio_wmb(bool weak_barriers) 42 { 43 if (weak_barriers) 44 smp_wmb(); 45 else 46 wmb(); 47 } 48 #else 49 static inline void virtio_mb(bool weak_barriers) 50 { 51 mb(); 52 } 53 54 static inline void virtio_rmb(bool weak_barriers) 55 { 56 rmb(); 57 } 58 59 static inline void virtio_wmb(bool weak_barriers) 60 { 61 wmb(); 62 } 63 #endif 64 65 struct virtio_device; 66 struct virtqueue; 67 68 struct virtqueue *vring_new_virtqueue(unsigned int index, 69 unsigned int num, 70 unsigned int vring_align, 71 struct virtio_device *vdev, 72 bool weak_barriers, 73 void *pages, 74 void (*notify)(struct virtqueue *vq), 75 void (*callback)(struct virtqueue *vq), 76 const char *name); 77 void vring_del_virtqueue(struct virtqueue *vq); 78 /* Filter out transport-specific feature bits. */ 79 void vring_transport_features(struct virtio_device *vdev); 80 81 irqreturn_t vring_interrupt(int irq, void *_vq); 82 #endif /* _LINUX_VIRTIO_RING_H */ 83