u-boot/include/virtio_ring.h
Tuomas Tynkkynen c011641ec4 virtio: Add codes for virtual queue/ring management
This adds support for managing virtual queue/ring, the channel
for high performance I/O between host and guest.

Signed-off-by: Tuomas Tynkkynen <tuomas.tynkkynen@iki.fi>
Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
2018-11-14 09:16:27 -08:00

320 lines
9.4 KiB
C

/* SPDX-License-Identifier: BSD-3-Clause */
/*
* Copyright (C) 2018, Tuomas Tynkkynen <tuomas.tynkkynen@iki.fi>
* Copyright (C) 2018, Bin Meng <bmeng.cn@gmail.com>
*
* From Linux kernel include/uapi/linux/virtio_ring.h
*/
#ifndef _LINUX_VIRTIO_RING_H
#define _LINUX_VIRTIO_RING_H
#include <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
/*
* 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
/* 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
/* 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[];
};
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;
};
struct vring_used {
__virtio16 flags;
__virtio16 idx;
struct vring_used_elem ring[];
};
struct vring {
unsigned int num;
struct vring_desc *desc;
struct vring_avail *avail;
struct vring_used *used;
};
/**
* virtqueue - a queue to register buffers for sending or receiving.
*
* @list: the chain of virtqueues for this device
* @vdev: the virtio device this queue was created for
* @index: the zero-based ordinal number for this queue
* @num_free: number of elements we expect to be able to fit
* @vring: actual memory layout for this queue
* @event: host publishes avail event idx
* @free_head: head of free buffer list
* @num_added: number we've added since last sync
* @last_used_idx: last used index we've seen
* @avail_flags_shadow: last written value to avail->flags
* @avail_idx_shadow: last written value to avail->idx in guest byte order
*/
struct virtqueue {
struct list_head list;
struct udevice *vdev;
unsigned int index;
unsigned int num_free;
struct vring vring;
bool event;
unsigned int free_head;
unsigned int num_added;
u16 last_used_idx;
u16 avail_flags_shadow;
u16 avail_idx_shadow;
};
/*
* 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
/*
* 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 = p + num * sizeof(struct vring_desc);
vr->used = (void *)(((uintptr_t)&vr->avail->ring[num] +
sizeof(__virtio16) + align - 1) & ~(align - 1));
}
static inline unsigned int 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;
}
/*
* 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 virtio_sg;
/**
* virtqueue_add - expose buffers to other end
*
* @vq: the struct virtqueue we're talking about
* @sgs: array of terminated scatterlists
* @out_sgs: the number of scatterlists readable by other side
* @in_sgs: the number of scatterlists which are writable
* (after readable ones)
*
* Caller must ensure we don't call this with other virtqueue operations
* at the same time (except where noted).
*
* Returns zero or a negative error (ie. ENOSPC, ENOMEM, EIO).
*/
int virtqueue_add(struct virtqueue *vq, struct virtio_sg *sgs[],
unsigned int out_sgs, unsigned int in_sgs);
/**
* virtqueue_kick - update after add_buf
*
* @vq: the struct virtqueue
*
* After one or more virtqueue_add() calls, invoke this to kick
* the other side.
*
* Caller must ensure we don't call this with other virtqueue
* operations at the same time (except where noted).
*/
void virtqueue_kick(struct virtqueue *vq);
/**
* virtqueue_get_buf - get the next used buffer
*
* @vq: the struct virtqueue we're talking about
* @len: the length written into the buffer
*
* If the device wrote data into the buffer, @len will be set to the
* amount written. This means you don't need to clear the buffer
* beforehand to ensure there's no data leakage in the case of short
* writes.
*
* Caller must ensure we don't call this with other virtqueue
* operations at the same time (except where noted).
*
* Returns NULL if there are no used buffers, or the memory buffer
* handed to virtqueue_add_*().
*/
void *virtqueue_get_buf(struct virtqueue *vq, unsigned int *len);
/**
* vring_create_virtqueue - create a virtqueue for a virtio device
*
* @index: the index of the queue
* @num: number of elements of the queue
* @vring_align:the alignment requirement of the descriptor ring
* @udev: the virtio transport udevice
* @return: the virtqueue pointer or NULL if failed
*
* This creates a virtqueue and allocates the descriptor ring for a virtio
* device. The caller should query virtqueue_get_ring_size() to learn the
* actual size of the ring.
*
* This API is supposed to be called by the virtio transport driver in the
* virtio find_vqs() uclass method.
*/
struct virtqueue *vring_create_virtqueue(unsigned int index, unsigned int num,
unsigned int vring_align,
struct udevice *udev);
/**
* vring_del_virtqueue - destroy a virtqueue
*
* @vq: the struct virtqueue we're talking about
*
* This destroys a virtqueue. If created with vring_create_virtqueue(),
* this also frees the descriptor ring.
*
* This API is supposed to be called by the virtio transport driver in the
* virtio del_vqs() uclass method.
*/
void vring_del_virtqueue(struct virtqueue *vq);
/**
* virtqueue_get_vring_size - get the size of the virtqueue's vring
*
* @vq: the struct virtqueue containing the vring of interest
* @return: the size of the vring in a virtqueue.
*/
unsigned int virtqueue_get_vring_size(struct virtqueue *vq);
/**
* virtqueue_get_desc_addr - get the vring descriptor table address
*
* @vq: the struct virtqueue containing the vring of interest
* @return: the descriptor table address of the vring in a virtqueue.
*/
ulong virtqueue_get_desc_addr(struct virtqueue *vq);
/**
* virtqueue_get_avail_addr - get the vring available ring address
*
* @vq: the struct virtqueue containing the vring of interest
* @return: the available ring address of the vring in a virtqueue.
*/
ulong virtqueue_get_avail_addr(struct virtqueue *vq);
/**
* virtqueue_get_used_addr - get the vring used ring address
*
* @vq: the struct virtqueue containing the vring of interest
* @return: the used ring address of the vring in a virtqueue.
*/
ulong virtqueue_get_used_addr(struct virtqueue *vq);
/**
* virtqueue_poll - query pending used buffers
*
* @vq: the struct virtqueue we're talking about
* @last_used_idx: virtqueue last used index
*
* Returns "true" if there are pending used buffers in the queue.
*/
bool virtqueue_poll(struct virtqueue *vq, u16 last_used_idx);
/**
* virtqueue_dump - dump the virtqueue for debugging
*
* @vq: the struct virtqueue we're talking about
*
* Caller must ensure we don't call this with other virtqueue operations
* at the same time (except where noted).
*/
void virtqueue_dump(struct virtqueue *vq);
/*
* Barriers in virtio are tricky. Since we are not in a hyperviosr/guest
* scenario, having these as nops is enough to work as expected.
*/
static inline void virtio_mb(void)
{
}
static inline void virtio_rmb(void)
{
}
static inline void virtio_wmb(void)
{
}
static inline void virtio_store_mb(__virtio16 *p, __virtio16 v)
{
WRITE_ONCE(*p, v);
}
#endif /* _LINUX_VIRTIO_RING_H */