#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 … /* This marks a buffer as write-only (otherwise read-only). */ #define VRING_DESC_F_WRITE … /* This means the buffer contains a list of buffer descriptors. */ #define VRING_DESC_F_INDIRECT … /* * 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 … #define VRING_PACKED_DESC_F_USED … /* 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 … /* 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 … /* Enable events in packed ring. */ #define VRING_PACKED_EVENT_FLAG_ENABLE … /* Disable events in packed ring. */ #define VRING_PACKED_EVENT_FLAG_DISABLE … /* * 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 … /* * Wrap counter bit shift in event suppression structure * of packed ring. */ #define VRING_PACKED_EVENT_F_WRAP_CTR … /* We support indirect buffer descriptors */ #define VIRTIO_RING_F_INDIRECT_DESC … /* 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 … /* Alignment requirements for vring elements. * When using pre-virtio 1.0 layout, these fall out naturally. */ #define VRING_AVAIL_ALIGN_SIZE … #define VRING_USED_ALIGN_SIZE … #define VRING_DESC_ALIGN_SIZE … /** * 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 { … }; struct vring_avail { … }; /* u32 is used here for ids for padding reasons. */ struct vring_used_elem { … }; vring_used_elem_t; struct vring_used { … }; /* * 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. */ vring_desc_t; vring_avail_t; vring_used_t; struct vring { … }; #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) … #define vring_avail_event(vr) … static inline void vring_init(struct vring *vr, unsigned int num, void *p, unsigned long align) { … } static inline unsigned vring_size(unsigned int num, unsigned long align) { … } #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) { … } struct vring_packed_desc_event { … }; struct vring_packed_desc { … }; #endif /* _UAPI_LINUX_VIRTIO_RING_H */
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