uapi/linux/virtio_ring.h

42 /* This marks a buffer as write-only (otherwise read-only). */
54 /* The Host uses this in used->flags to advise the Guest: don't kick me when
55  * you add a buffer.  It's unreliable, so it's simply an optimization.  Guest
58 /* The Guest uses this in avail->flags to advise the Host: don't interrupt me
83 /* The Guest publishes the used index for which it expects an interrupt
84  * at the end of the avail ring. Host should ignore the avail->flags field. */
86  * at the end of the used ring. Guest should ignore the used->flags field. */
90  * When using pre-virtio 1.0 layout, these fall out naturally.
97  * struct vring_desc - Virtio ring descriptors,
100  * @addr: buffer address (guest-physical)
120 /* u32 is used here for ids for padding reasons. */
139  * alignments assumptions. Thus, we might need to decrease the compiler-selected
143  * https://gcc.gnu.org/onlinedocs//gcc/Common-Type-Attributes.html#Common-Type-Attributes
159 	unsigned int num;  member
171  * like this.  We assume num is a power of 2.
176  *	struct vring_desc desc[num];
178  *	// A ring of available descriptor heads with free-running index.
181  *	__virtio16 available[num];
187  *	// A ring of used descriptor heads with free-running index.
190  *	struct vring_used_elem used[num];
196 #define vring_used_event(vr) ((vr)->avail->ring[(vr)->num])
197 #define vring_avail_event(vr) (*(__virtio16 *)&(vr)->used->ring[(vr)->num])
199 static inline void vring_init(struct vring *vr, unsigned int num, void *p,  in vring_init()  argument
202 	vr->num = num;  in vring_init()
203 	vr->desc = p;  in vring_init()
204 	vr->avail = (struct vring_avail *)((char *)p + num * sizeof(struct vring_desc));  in vring_init()
205 	vr->used = (void *)(((uintptr_t)&vr->avail->ring[num] + sizeof(__virtio16)  in vring_init()
206 		+ align-1) & ~(align - 1));  in vring_init()
209 static inline unsigned vring_size(unsigned int num, unsigned long align)  in vring_size()  argument
211 	return ((sizeof(struct vring_desc) * num + sizeof(__virtio16) * (3 + num)  in vring_size()
212 		 + align - 1) & ~(align - 1))  in vring_size()
213 		+ sizeof(__virtio16) * 3 + sizeof(struct vring_used_elem) * num;  in vring_size()
224 	/* Note: Xen has similar logic for notification hold-off  in vring_need_event()
229 	return (__u16)(new_idx - event_idx - 1) < (__u16)(new_idx - old);  in vring_need_event()