include/uapi/linux/virtio_ring.h - third_party/kernel - Git at Google

 #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

 /* Virtio ring descriptors: 16 bytes.  These can chain together via "next". */
 struct vring_desc {
 	/* Address (guest-physical). */
 	__virtio64 addr;
 	/* Length. */
 	__virtio32 len;
 	/* The flags as indicated above. */
 	__virtio16 flags;
 	/* We chain unused descriptors via this, too */
 	__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 */
	#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

	/* Virtio ring descriptors: 16 bytes. These can chain together via "next". */
	struct vring_desc {
	/* Address (guest-physical). */
	__virtio64 addr;
	/* Length. */
	__virtio32 len;
	/* The flags as indicated above. */
	__virtio16 flags;
	/* We chain unused descriptors via this, too */
	__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 */