diff options
Diffstat (limited to 'include/uapi/linux/virtio_ring.h')
| -rw-r--r-- | include/uapi/linux/virtio_ring.h | 112 |
1 files changed, 94 insertions, 18 deletions
diff --git a/include/uapi/linux/virtio_ring.h b/include/uapi/linux/virtio_ring.h index c07295969b7e..f8c20d3de8da 100644 --- a/include/uapi/linux/virtio_ring.h +++ b/include/uapi/linux/virtio_ring.h @@ -1,7 +1,7 @@ #ifndef _UAPI_LINUX_VIRTIO_RING_H #define _UAPI_LINUX_VIRTIO_RING_H -/* An interface for efficient virtio implementation, currently for use by KVM - * and lguest, but hopefully others soon. Do NOT change this since it will +/* 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 @@ -44,6 +44,13 @@ /* 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. */ @@ -53,6 +60,23 @@ * 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 @@ -62,15 +86,28 @@ * at the end of the used ring. Guest should ignore the used->flags field. */ #define VIRTIO_RING_F_EVENT_IDX 29 -/* Virtio ring descriptors: 16 bytes. These can chain together via "next". */ +/* 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 { - /* Address (guest-physical). */ __virtio64 addr; - /* Length. */ __virtio32 len; - /* The flags as indicated above. */ __virtio16 flags; - /* We chain unused descriptors via this, too */ __virtio16 next; }; @@ -88,28 +125,47 @@ struct vring_used_elem { __virtio32 len; }; +typedef struct vring_used_elem __attribute__((aligned(VRING_USED_ALIGN_SIZE))) + vring_used_elem_t; + struct vring_used { __virtio16 flags; __virtio16 idx; - struct vring_used_elem ring[]; + 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; - struct vring_desc *desc; + vring_desc_t *desc; - struct vring_avail *avail; + vring_avail_t *avail; - struct vring_used *used; + vring_used_t *used; }; -/* 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 +#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. @@ -145,7 +201,7 @@ static inline void vring_init(struct vring *vr, unsigned int num, void *p, { vr->num = num; vr->desc = p; - vr->avail = p + num*sizeof(struct vring_desc); + 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)); } @@ -157,6 +213,8 @@ static inline unsigned vring_size(unsigned int num, unsigned long align) + 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, @@ -171,4 +229,22 @@ static inline int vring_need_event(__u16 event_idx, __u16 new_idx, __u16 old) 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 */ |