| #ifndef _UAPI_LINUX_VIRTIO_RING_H |
| #define _UAPI_LINUX_VIRTIO_RING_H |
| /* An interface for efficient virtio implementation, currently for use by KVM, |
| * but hopefully others soon. Do NOT change this since it will |
| * break existing servers and clients. |
| * |
| * This header is BSD licensed so anyone can use the definitions to implement |
| * compatible drivers/servers. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * 1. Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * 2. Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in the |
| * documentation and/or other materials provided with the distribution. |
| * 3. Neither the name of IBM nor the names of its contributors |
| * may be used to endorse or promote products derived from this software |
| * without specific prior written permission. |
| * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ``AS IS'' AND |
| * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
| * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
| * ARE DISCLAIMED. IN NO EVENT SHALL IBM OR CONTRIBUTORS BE LIABLE |
| * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
| * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
| * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
| * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
| * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
| * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
| * SUCH DAMAGE. |
| * |
| * Copyright Rusty Russell IBM Corporation 2007. */ |
| #ifndef __KERNEL__ |
| #include <stdint.h> |
| #endif |
| #include <linux/types.h> |
| #include <linux/virtio_types.h> |
| |
| /* This marks a buffer as continuing via the next field. */ |
| #define VRING_DESC_F_NEXT 1 |
| /* This marks a buffer as write-only (otherwise read-only). */ |
| #define VRING_DESC_F_WRITE 2 |
| /* This means the buffer contains a list of buffer descriptors. */ |
| #define VRING_DESC_F_INDIRECT 4 |
| |
| /* |
| * Mark a descriptor as available or used in packed ring. |
| * Notice: they are defined as shifts instead of shifted values. |
| */ |
| #define VRING_PACKED_DESC_F_AVAIL 7 |
| #define VRING_PACKED_DESC_F_USED 15 |
| |
| /* The Host uses this in used->flags to advise the Guest: don't kick me when |
| * you add a buffer. It's unreliable, so it's simply an optimization. Guest |
| * will still kick if it's out of buffers. */ |
| #define VRING_USED_F_NO_NOTIFY 1 |
| /* The Guest uses this in avail->flags to advise the Host: don't interrupt me |
| * when you consume a buffer. It's unreliable, so it's simply an |
| * optimization. */ |
| #define VRING_AVAIL_F_NO_INTERRUPT 1 |
| |
| /* Enable events in packed ring. */ |
| #define VRING_PACKED_EVENT_FLAG_ENABLE 0x0 |
| /* Disable events in packed ring. */ |
| #define VRING_PACKED_EVENT_FLAG_DISABLE 0x1 |
| /* |
| * Enable events for a specific descriptor in packed ring. |
| * (as specified by Descriptor Ring Change Event Offset/Wrap Counter). |
| * Only valid if VIRTIO_RING_F_EVENT_IDX has been negotiated. |
| */ |
| #define VRING_PACKED_EVENT_FLAG_DESC 0x2 |
| |
| /* |
| * Wrap counter bit shift in event suppression structure |
| * of packed ring. |
| */ |
| #define VRING_PACKED_EVENT_F_WRAP_CTR 15 |
| |
| /* We support indirect buffer descriptors */ |
| #define VIRTIO_RING_F_INDIRECT_DESC 28 |
| |
| /* The Guest publishes the used index for which it expects an interrupt |
| * at the end of the avail ring. Host should ignore the avail->flags field. */ |
| /* The Host publishes the avail index for which it expects a kick |
| * at the end of the used ring. Guest should ignore the used->flags field. */ |
| #define VIRTIO_RING_F_EVENT_IDX 29 |
| |
| /* Alignment requirements for vring elements. |
| * When using pre-virtio 1.0 layout, these fall out naturally. |
| */ |
| #define VRING_AVAIL_ALIGN_SIZE 2 |
| #define VRING_USED_ALIGN_SIZE 4 |
| #define VRING_DESC_ALIGN_SIZE 16 |
| |
| /** |
| * struct vring_desc - Virtio ring descriptors, |
| * 16 bytes long. These can chain together via @next. |
| * |
| * @addr: buffer address (guest-physical) |
| * @len: buffer length |
| * @flags: descriptor flags |
| * @next: index of the next descriptor in the chain, |
| * if the VRING_DESC_F_NEXT flag is set. We chain unused |
| * descriptors via this, too. |
| */ |
| struct vring_desc { |
| __virtio64 addr; |
| __virtio32 len; |
| __virtio16 flags; |
| __virtio16 next; |
| }; |
| |
| struct vring_avail { |
| __virtio16 flags; |
| __virtio16 idx; |
| __virtio16 ring[]; |
| }; |
| |
| /* u32 is used here for ids for padding reasons. */ |
| struct vring_used_elem { |
| /* Index of start of used descriptor chain. */ |
| __virtio32 id; |
| /* Total length of the descriptor chain which was used (written to) */ |
| __virtio32 len; |
| }; |
| |
| typedef struct vring_used_elem __attribute__((aligned(VRING_USED_ALIGN_SIZE))) |
| vring_used_elem_t; |
| |
| struct vring_used { |
| __virtio16 flags; |
| __virtio16 idx; |
| vring_used_elem_t ring[]; |
| }; |
| |
| /* |
| * The ring element addresses are passed between components with different |
| * alignments assumptions. Thus, we might need to decrease the compiler-selected |
| * alignment, and so must use a typedef to make sure the aligned attribute |
| * actually takes hold: |
| * |
| * https://gcc.gnu.org/onlinedocs//gcc/Common-Type-Attributes.html#Common-Type-Attributes |
| * |
| * When used on a struct, or struct member, the aligned attribute can only |
| * increase the alignment; in order to decrease it, the packed attribute must |
| * be specified as well. When used as part of a typedef, the aligned attribute |
| * can both increase and decrease alignment, and specifying the packed |
| * attribute generates a warning. |
| */ |
| typedef struct vring_desc __attribute__((aligned(VRING_DESC_ALIGN_SIZE))) |
| vring_desc_t; |
| typedef struct vring_avail __attribute__((aligned(VRING_AVAIL_ALIGN_SIZE))) |
| vring_avail_t; |
| typedef struct vring_used __attribute__((aligned(VRING_USED_ALIGN_SIZE))) |
| vring_used_t; |
| |
| struct vring { |
| unsigned int num; |
| |
| vring_desc_t *desc; |
| |
| vring_avail_t *avail; |
| |
| vring_used_t *used; |
| }; |
| |
| #ifndef VIRTIO_RING_NO_LEGACY |
| |
| /* The standard layout for the ring is a continuous chunk of memory which looks |
| * like this. We assume num is a power of 2. |
| * |
| * struct vring |
| * { |
| * // The actual descriptors (16 bytes each) |
| * struct vring_desc desc[num]; |
| * |
| * // A ring of available descriptor heads with free-running index. |
| * __virtio16 avail_flags; |
| * __virtio16 avail_idx; |
| * __virtio16 available[num]; |
| * __virtio16 used_event_idx; |
| * |
| * // Padding to the next align boundary. |
| * char pad[]; |
| * |
| * // A ring of used descriptor heads with free-running index. |
| * __virtio16 used_flags; |
| * __virtio16 used_idx; |
| * struct vring_used_elem used[num]; |
| * __virtio16 avail_event_idx; |
| * }; |
| */ |
| /* We publish the used event index at the end of the available ring, and vice |
| * versa. They are at the end for backwards compatibility. */ |
| #define vring_used_event(vr) ((vr)->avail->ring[(vr)->num]) |
| #define vring_avail_event(vr) (*(__virtio16 *)&(vr)->used->ring[(vr)->num]) |
| |
| static inline void vring_init(struct vring *vr, unsigned int num, void *p, |
| unsigned long align) |
| { |
| vr->num = num; |
| vr->desc = p; |
| vr->avail = (struct vring_avail *)((char *)p + num * sizeof(struct vring_desc)); |
| vr->used = (void *)(((uintptr_t)&vr->avail->ring[num] + sizeof(__virtio16) |
| + align-1) & ~(align - 1)); |
| } |
| |
| static inline unsigned vring_size(unsigned int num, unsigned long align) |
| { |
| return ((sizeof(struct vring_desc) * num + sizeof(__virtio16) * (3 + num) |
| + align - 1) & ~(align - 1)) |
| + sizeof(__virtio16) * 3 + sizeof(struct vring_used_elem) * num; |
| } |
| |
| #endif /* VIRTIO_RING_NO_LEGACY */ |
| |
| /* The following is used with USED_EVENT_IDX and AVAIL_EVENT_IDX */ |
| /* Assuming a given event_idx value from the other side, if |
| * we have just incremented index from old to new_idx, |
| * should we trigger an event? */ |
| static inline int vring_need_event(__u16 event_idx, __u16 new_idx, __u16 old) |
| { |
| /* Note: Xen has similar logic for notification hold-off |
| * in include/xen/interface/io/ring.h with req_event and req_prod |
| * corresponding to event_idx + 1 and new_idx respectively. |
| * Note also that req_event and req_prod in Xen start at 1, |
| * event indexes in virtio start at 0. */ |
| return (__u16)(new_idx - event_idx - 1) < (__u16)(new_idx - old); |
| } |
| |
| struct vring_packed_desc_event { |
| /* Descriptor Ring Change Event Offset/Wrap Counter. */ |
| __le16 off_wrap; |
| /* Descriptor Ring Change Event Flags. */ |
| __le16 flags; |
| }; |
| |
| struct vring_packed_desc { |
| /* Buffer Address. */ |
| __le64 addr; |
| /* Buffer Length. */ |
| __le32 len; |
| /* Buffer ID. */ |
| __le16 id; |
| /* The flags depending on descriptor type. */ |
| __le16 flags; |
| }; |
| |
| #endif /* _UAPI_LINUX_VIRTIO_RING_H */ |