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 /* This means the buffer contains a list of buffer descriptors. */ 18 #define VRING_DESC_F_INDIRECT 4 19 20 /* The Host uses this in used->flags to advise the Guest: don't kick me when 21 * you add a buffer. It's unreliable, so it's simply an optimization. Guest 22 * will still kick if it's out of buffers. */ 23 #define VRING_USED_F_NO_NOTIFY 1 24 /* The Guest uses this in avail->flags to advise the Host: don't interrupt me 25 * when you consume a buffer. It's unreliable, so it's simply an 26 * optimization. */ 27 #define VRING_AVAIL_F_NO_INTERRUPT 1 28 29 /* We support indirect buffer descriptors */ 30 #define VIRTIO_RING_F_INDIRECT_DESC 28 31 32 /* Virtio ring descriptors: 16 bytes. These can chain together via "next". */ 33 struct vring_desc 34 { 35 /* Address (guest-physical). */ 36 __u64 addr; 37 /* Length. */ 38 __u32 len; 39 /* The flags as indicated above. */ 40 __u16 flags; 41 /* We chain unused descriptors via this, too */ 42 __u16 next; 43 }; 44 45 struct vring_avail 46 { 47 __u16 flags; 48 __u16 idx; 49 __u16 ring[]; 50 }; 51 52 /* u32 is used here for ids for padding reasons. */ 53 struct vring_used_elem 54 { 55 /* Index of start of used descriptor chain. */ 56 __u32 id; 57 /* Total length of the descriptor chain which was used (written to) */ 58 __u32 len; 59 }; 60 61 struct vring_used 62 { 63 __u16 flags; 64 __u16 idx; 65 struct vring_used_elem ring[]; 66 }; 67 68 struct vring { 69 unsigned int num; 70 71 struct vring_desc *desc; 72 73 struct vring_avail *avail; 74 75 struct vring_used *used; 76 }; 77 78 /* The standard layout for the ring is a continuous chunk of memory which looks 79 * like this. We assume num is a power of 2. 80 * 81 * struct vring 82 * { 83 * // The actual descriptors (16 bytes each) 84 * struct vring_desc desc[num]; 85 * 86 * // A ring of available descriptor heads with free-running index. 87 * __u16 avail_flags; 88 * __u16 avail_idx; 89 * __u16 available[num]; 90 * 91 * // Padding to the next align boundary. 92 * char pad[]; 93 * 94 * // A ring of used descriptor heads with free-running index. 95 * __u16 used_flags; 96 * __u16 used_idx; 97 * struct vring_used_elem used[num]; 98 * }; 99 */ 100 static inline void vring_init(struct vring *vr, unsigned int num, void *p, 101 unsigned long align) 102 { 103 vr->num = num; 104 vr->desc = p; 105 vr->avail = p + num*sizeof(struct vring_desc); 106 vr->used = (void *)(((unsigned long)&vr->avail->ring[num] + align-1) 107 & ~(align - 1)); 108 } 109 110 static inline unsigned vring_size(unsigned int num, unsigned long align) 111 { 112 return ((sizeof(struct vring_desc) * num + sizeof(__u16) * (2 + num) 113 + align - 1) & ~(align - 1)) 114 + sizeof(__u16) * 2 + sizeof(struct vring_used_elem) * num; 115 } 116 117 #ifdef __KERNEL__ 118 #include <linux/irqreturn.h> 119 struct virtio_device; 120 struct virtqueue; 121 122 struct virtqueue *vring_new_virtqueue(unsigned int num, 123 unsigned int vring_align, 124 struct virtio_device *vdev, 125 void *pages, 126 void (*notify)(struct virtqueue *vq), 127 void (*callback)(struct virtqueue *vq), 128 const char *name); 129 void vring_del_virtqueue(struct virtqueue *vq); 130 /* Filter out transport-specific feature bits. */ 131 void vring_transport_features(struct virtio_device *vdev); 132 133 irqreturn_t vring_interrupt(int irq, void *_vq); 134 #endif /* __KERNEL__ */ 135 #endif /* _LINUX_VIRTIO_RING_H */ 136