1 #ifndef _LINUX_VIRTIO_RING_H 2 #define _LINUX_VIRTIO_RING_H 3 /* An interface for efficient virtio implementation, currently for use by KVM 4 * and lguest, but hopefully others soon. Do NOT change this since it will 5 * break existing servers and clients. 6 * 7 * This header is BSD licensed so anyone can use the definitions to implement 8 * compatible drivers/servers. 9 * 10 * Copyright Rusty Russell IBM Corporation 2007. */ 11 #include <linux/types.h> 12 13 /* This marks a buffer as continuing via the next field. */ 14 #define VRING_DESC_F_NEXT 1 15 /* This marks a buffer as write-only (otherwise read-only). */ 16 #define VRING_DESC_F_WRITE 2 17 18 /* This means don't notify other side when buffer added. */ 19 #define VRING_USED_F_NO_NOTIFY 1 20 /* This means don't interrupt guest when buffer consumed. */ 21 #define VRING_AVAIL_F_NO_INTERRUPT 1 22 23 /* Virtio ring descriptors: 16 bytes. These can chain together via "next". */ 24 struct vring_desc 25 { 26 /* Address (guest-physical). */ 27 __u64 addr; 28 /* Length. */ 29 __u32 len; 30 /* The flags as indicated above. */ 31 __u16 flags; 32 /* We chain unused descriptors via this, too */ 33 __u16 next; 34 }; 35 36 struct vring_avail 37 { 38 __u16 flags; 39 __u16 idx; 40 __u16 ring[]; 41 }; 42 43 /* u32 is used here for ids for padding reasons. */ 44 struct vring_used_elem 45 { 46 /* Index of start of used descriptor chain. */ 47 __u32 id; 48 /* Total length of the descriptor chain which was used (written to) */ 49 __u32 len; 50 }; 51 52 struct vring_used 53 { 54 __u16 flags; 55 __u16 idx; 56 struct vring_used_elem ring[]; 57 }; 58 59 struct vring { 60 unsigned int num; 61 62 struct vring_desc *desc; 63 64 struct vring_avail *avail; 65 66 struct vring_used *used; 67 }; 68 69 /* The standard layout for the ring is a continuous chunk of memory which looks 70 * like this. We assume num is a power of 2. 71 * 72 * struct vring 73 * { 74 * // The actual descriptors (16 bytes each) 75 * struct vring_desc desc[num]; 76 * 77 * // A ring of available descriptor heads with free-running index. 78 * __u16 avail_flags; 79 * __u16 avail_idx; 80 * __u16 available[num]; 81 * 82 * // Padding to the next page boundary. 83 * char pad[]; 84 * 85 * // A ring of used descriptor heads with free-running index. 86 * __u16 used_flags; 87 * __u16 used_idx; 88 * struct vring_used_elem used[num]; 89 * }; 90 */ 91 static inline void vring_init(struct vring *vr, unsigned int num, void *p, 92 unsigned int pagesize) 93 { 94 vr->num = num; 95 vr->desc = p; 96 vr->avail = p + num*sizeof(struct vring_desc); 97 vr->used = (void *)(((unsigned long)&vr->avail->ring[num] + pagesize-1) 98 & ~(pagesize - 1)); 99 } 100 101 static inline unsigned vring_size(unsigned int num, unsigned int pagesize) 102 { 103 return ((sizeof(struct vring_desc) * num + sizeof(__u16) * (2 + num) 104 + pagesize - 1) & ~(pagesize - 1)) 105 + sizeof(__u16) * 2 + sizeof(struct vring_used_elem) * num; 106 } 107 108 #ifdef __KERNEL__ 109 #include <linux/irqreturn.h> 110 struct virtio_device; 111 struct virtqueue; 112 113 struct virtqueue *vring_new_virtqueue(unsigned int num, 114 struct virtio_device *vdev, 115 void *pages, 116 void (*notify)(struct virtqueue *vq), 117 bool (*callback)(struct virtqueue *vq)); 118 void vring_del_virtqueue(struct virtqueue *vq); 119 120 irqreturn_t vring_interrupt(int irq, void *_vq); 121 #endif /* __KERNEL__ */ 122 #endif /* _LINUX_VIRTIO_RING_H */ 123