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 /* The Host uses this in used->flags to advise the Guest: don't kick me when 19 * you add a buffer. It's unreliable, so it's simply an optimization. Guest 20 * will still kick if it's out of buffers. */ 21 #define VRING_USED_F_NO_NOTIFY 1 22 /* The Guest uses this in avail->flags to advise the Host: don't interrupt me 23 * when you consume a buffer. It's unreliable, so it's simply an 24 * optimization. */ 25 #define VRING_AVAIL_F_NO_INTERRUPT 1 26 27 /* Virtio ring descriptors: 16 bytes. These can chain together via "next". */ 28 struct vring_desc 29 { 30 /* Address (guest-physical). */ 31 __u64 addr; 32 /* Length. */ 33 __u32 len; 34 /* The flags as indicated above. */ 35 __u16 flags; 36 /* We chain unused descriptors via this, too */ 37 __u16 next; 38 }; 39 40 struct vring_avail 41 { 42 __u16 flags; 43 __u16 idx; 44 __u16 ring[]; 45 }; 46 47 /* u32 is used here for ids for padding reasons. */ 48 struct vring_used_elem 49 { 50 /* Index of start of used descriptor chain. */ 51 __u32 id; 52 /* Total length of the descriptor chain which was used (written to) */ 53 __u32 len; 54 }; 55 56 struct vring_used 57 { 58 __u16 flags; 59 __u16 idx; 60 struct vring_used_elem ring[]; 61 }; 62 63 struct vring { 64 unsigned int num; 65 66 struct vring_desc *desc; 67 68 struct vring_avail *avail; 69 70 struct vring_used *used; 71 }; 72 73 /* The standard layout for the ring is a continuous chunk of memory which looks 74 * like this. We assume num is a power of 2. 75 * 76 * struct vring 77 * { 78 * // The actual descriptors (16 bytes each) 79 * struct vring_desc desc[num]; 80 * 81 * // A ring of available descriptor heads with free-running index. 82 * __u16 avail_flags; 83 * __u16 avail_idx; 84 * __u16 available[num]; 85 * 86 * // Padding to the next page boundary. 87 * char pad[]; 88 * 89 * // A ring of used descriptor heads with free-running index. 90 * __u16 used_flags; 91 * __u16 used_idx; 92 * struct vring_used_elem used[num]; 93 * }; 94 */ 95 static inline void vring_init(struct vring *vr, unsigned int num, void *p, 96 unsigned long pagesize) 97 { 98 vr->num = num; 99 vr->desc = p; 100 vr->avail = p + num*sizeof(struct vring_desc); 101 vr->used = (void *)(((unsigned long)&vr->avail->ring[num] + pagesize-1) 102 & ~(pagesize - 1)); 103 } 104 105 static inline unsigned vring_size(unsigned int num, unsigned long pagesize) 106 { 107 return ((sizeof(struct vring_desc) * num + sizeof(__u16) * (2 + num) 108 + pagesize - 1) & ~(pagesize - 1)) 109 + sizeof(__u16) * 2 + sizeof(struct vring_used_elem) * num; 110 } 111 112 #ifdef __KERNEL__ 113 #include <linux/irqreturn.h> 114 struct virtio_device; 115 struct virtqueue; 116 117 struct virtqueue *vring_new_virtqueue(unsigned int num, 118 struct virtio_device *vdev, 119 void *pages, 120 void (*notify)(struct virtqueue *vq), 121 void (*callback)(struct virtqueue *vq)); 122 void vring_del_virtqueue(struct virtqueue *vq); 123 /* Filter out transport-specific feature bits. */ 124 void vring_transport_features(struct virtio_device *vdev); 125 126 irqreturn_t vring_interrupt(int irq, void *_vq); 127 #endif /* __KERNEL__ */ 128 #endif /* _LINUX_VIRTIO_RING_H */ 129