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
58 /* The Guest uses this in avail->flags to advise the Host: don't interrupt me
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.
98 	/* Address (guest-physical). */
132  * The ring element addresses are passed between components with different
133  * alignments assumptions. Thus, we might need to decrease the compiler-selected
137  * https://gcc.gnu.org/onlinedocs//gcc/Common-Type-Attributes.html#Common-Type-Attributes
153 	unsigned int num;  member
165  * like this.  We assume num is a power of 2.
170  *	struct vring_desc desc[num];
172  *	// A ring of available descriptor heads with free-running index.
175  *	__virtio16 available[num];
181  *	// A ring of used descriptor heads with free-running index.
184  *	struct vring_used_elem used[num];
190 #define vring_used_event(vr) ((vr)->avail->ring[(vr)->num])
191 #define vring_avail_event(vr) (*(__virtio16 *)&(vr)->used->ring[(vr)->num])
193 static inline void vring_init(struct vring *vr, unsigned int num, void *p,  in vring_init()  argument
196 	vr->num = num;  in vring_init()
197 	vr->desc = p;  in vring_init()
198 	vr->avail = (struct vring_avail *)((char *)p + num * sizeof(struct vring_desc));  in vring_init()
199 	vr->used = (void *)(((uintptr_t)&vr->avail->ring[num] + sizeof(__virtio16)  in vring_init()
200 		+ align-1) & ~(align - 1));  in vring_init()
203 static inline unsigned vring_size(unsigned int num, unsigned long align)  in vring_size()  argument
205 	return ((sizeof(struct vring_desc) * num + sizeof(__virtio16) * (3 + num)  in vring_size()
206 		 + align - 1) & ~(align - 1))  in vring_size()
207 		+ sizeof(__virtio16) * 3 + sizeof(struct vring_used_elem) * num;  in vring_size()
218 	/* Note: Xen has similar logic for notification hold-off  in vring_need_event()
223 	return (__u16)(new_idx - event_idx - 1) < (__u16)(new_idx - old);  in vring_need_event()