standard-headers/linux/virtio_ring.h

35 #include "standard-headers/linux/types.h"
36 #include "standard-headers/linux/virtio_types.h"
40 /* This marks a buffer as write-only (otherwise read-only). */
52 /* The Host uses this in used->flags to advise the Guest: don't kick me when
56 /* The Guest uses this in avail->flags to advise the Host: don't interrupt me
63 /* Disable events in packed ring. */
82  * at the end of the avail ring. Host should ignore the avail->flags field. */
84  * at the end of the used ring. Guest should ignore the used->flags field. */
88  * When using pre-virtio 1.0 layout, these fall out naturally.
95  * struct vring_desc - Virtio ring descriptors,
98  * @addr: buffer address (guest-physical)
137  * alignments assumptions. Thus, we might need to decrease the compiler-selected
141  * https://gcc.gnu.org/onlinedocs//gcc/Common-Type-Attributes.html#Common-Type-Attributes
176  *	// A ring of available descriptor heads with free-running index.
185  *	// A ring of used descriptor heads with free-running index.
194 #define vring_used_event(vr) ((vr)->avail->ring[(vr)->num])
195 #define vring_avail_event(vr) (*(__virtio16 *)&(vr)->used->ring[(vr)->num])
200 	vr->num = num;  in vring_init()
201 	vr->desc = p;  in vring_init()
202 	vr->avail = (struct vring_avail *)((char *)p + num * sizeof(struct vring_desc));  in vring_init()
203 	vr->used = (void *)(((uintptr_t)&vr->avail->ring[num] + sizeof(__virtio16)  in vring_init()
204 		+ align-1) & ~(align - 1));  in vring_init()
210 		 + align - 1) & ~(align - 1))  in vring_size()
222 	/* Note: Xen has similar logic for notification hold-off  in vring_need_event()
223 	 * in include/xen/interface/io/ring.h with req_event and req_prod  in vring_need_event()
225 	 * Note also that req_event and req_prod in Xen start at 1,  in vring_need_event()
227 	return (uint16_t)(new_idx - event_idx - 1) < (uint16_t)(new_idx - old);  in vring_need_event()