Re: [PATCH 1/2] virtio: abstract virtqueue related methods

Michael S. Tsirkin
2023-05-12T10:47:20Z

On Fri, May 12, 2023 at 05:46:17PM +0800, zhenwei pi wrote:
> There is already a virtqueue abstract structure in virtio subsystem
> (see struct virtqueue in include/linux/virtio.h), however the vring
> based virtqueue is used only in the past years, the virtqueue related
> methods mix much with vring(just look like the codes, virtqueue_xxx
> functions are implemented in virtio_ring.c).
>
> Abstract virtqueue related methods(see struct virtqueue_ops), and
> separate virtqueue_xxx symbols from vring. This allows a non-vring
> based transport in the future. With this change, the following symbols
> are exported from virtio.ko instead of virtio_ring.ko:
> virtqueue_add_sgs
> virtqueue_add_outbuf
> virtqueue_add_inbuf
> virtqueue_add_inbuf_ctx
> virtqueue_kick_prepare
> virtqueue_notify
> virtqueue_kick
> virtqueue_enable_cb_prepare
> virtqueue_enable_cb
> virtqueue_enable_cb_delayed
> virtqueue_disable_cb
> virtqueue_poll
> virtqueue_get_buf_ctx
> virtqueue_get_buf
> virtqueue_detach_unused_buf
> virtqueue_get_vring_size
> virtqueue_resize
> virtqueue_is_broken
> virtio_break_device
> __virtio_unbreak_device
>
> Cc: Stefan Hajnoczi <stefanha@redhat.com>
> Signed-off-by: zhenwei pi <pizhenwei@bytedance.com>
> ---
> drivers/virtio/virtio.c | 362 +++++++++++++++++++++++++++++++++++
> drivers/virtio/virtio_ring.c | 282 +++++----------------------
> include/linux/virtio.h | 29 +++
> 3 files changed, 443 insertions(+), 230 deletions(-)
>
> diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
> index 3893dc29eb26..8d8715a10f26 100644
> --- a/drivers/virtio/virtio.c
> +++ b/drivers/virtio/virtio.c
> @@ -553,6 +553,368 @@ int virtio_device_restore(struct virtio_device *dev)
> EXPORT_SYMBOL_GPL(virtio_device_restore);
> #endif
>
> +/**
> + * virtqueue_add_sgs - 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)
> + * @data: the token identifying the buffer.
> + * @gfp: how to do memory allocations (if necessary).
> + *
> + * 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_sgs(struct virtqueue *vq, struct scatterlist *sgs[],
> + unsigned int out_sgs, unsigned int in_sgs,
> + void *data, gfp_t gfp)
> +{
> + unsigned int i, total_sg = 0;
> +
> + /* Count them first. */
> + for (i = 0; i < out_sgs + in_sgs; i++) {
> + struct scatterlist *sg;
> +
> + for (sg = sgs[i]; sg; sg = sg_next(sg))
> + total_sg++;
> + }
> + return vq->ops->add_sgs(vq, sgs, total_sg, out_sgs, in_sgs,
> + data, NULL, gfp);
> +}
> +EXPORT_SYMBOL_GPL(virtqueue_add_sgs);

Hmm this kind of indirection on data path is going to be costly
performance-wise especially when retpolines are in place.

Any data on this?

> +
> +/**
> + * virtqueue_add_outbuf - expose output buffers to other end
> + * @vq: the struct virtqueue we're talking about.
> + * @sg: scatterlist (must be well-formed and terminated!)
> + * @num: the number of entries in @sg readable by other side
> + * @data: the token identifying the buffer.
> + * @gfp: how to do memory allocations (if necessary).
> + *
> + * 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_outbuf(struct virtqueue *vq, struct scatterlist *sg,
> + unsigned int num, void *data, gfp_t gfp)
> +{
> + return vq->ops->add_sgs(vq, &sg, num, 1, 0, data, NULL, gfp);
> +}
> +EXPORT_SYMBOL_GPL(virtqueue_add_outbuf);
> +
> +/**
> + * virtqueue_add_inbuf - expose input buffers to other end
> + * @vq: the struct virtqueue we're talking about.
> + * @sg: scatterlist (must be well-formed and terminated!)
> + * @num: the number of entries in @sg writable by other side
> + * @data: the token identifying the buffer.
> + * @gfp: how to do memory allocations (if necessary).
> + *
> + * 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_inbuf(struct virtqueue *vq, struct scatterlist *sg,
> + unsigned int num, void *data, gfp_t gfp)
> +{
> + return vq->ops->add_sgs(vq, &sg, num, 0, 1, data, NULL, gfp);
> +}
> +EXPORT_SYMBOL_GPL(virtqueue_add_inbuf);
> +
> +/**
> + * virtqueue_add_inbuf_ctx - expose input buffers to other end
> + * @vq: the struct virtqueue we're talking about.
> + * @sg: scatterlist (must be well-formed and terminated!)
> + * @num: the number of entries in @sg writable by other side
> + * @data: the token identifying the buffer.
> + * @ctx: extra context for the token
> + * @gfp: how to do memory allocations (if necessary).
> + *
> + * 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_inbuf_ctx(struct virtqueue *vq, struct scatterlist *sg,
> + unsigned int num, void *data, void *ctx, gfp_t gfp)
> +{
> + return vq->ops->add_sgs(vq, &sg, num, 0, 1, data, ctx, gfp);
> +}
> +EXPORT_SYMBOL_GPL(virtqueue_add_inbuf_ctx);
> +
> +/**
> + * virtqueue_kick_prepare - first half of split virtqueue_kick call.
> + * @vq: the struct virtqueue
> + *
> + * Instead of virtqueue_kick(), you can do:
> + * if (virtqueue_kick_prepare(vq))
> + * virtqueue_notify(vq);
> + *
> + * This is sometimes useful because the virtqueue_kick_prepare() needs
> + * to be serialized, but the actual virtqueue_notify() call does not.
> + */
> +bool virtqueue_kick_prepare(struct virtqueue *vq)
> +{
> + return vq->ops->kick_prepare(vq);
> +}
> +EXPORT_SYMBOL_GPL(virtqueue_kick_prepare);
> +
> +/**
> + * virtqueue_notify - second half of split virtqueue_kick call.
> + * @vq: the struct virtqueue
> + *
> + * This does not need to be serialized.
> + *
> + * Returns false if host notify failed or queue is broken, otherwise true.
> + */
> +bool virtqueue_notify(struct virtqueue *vq)
> +{
> + return vq->ops->notify(vq);
> +}
> +EXPORT_SYMBOL_GPL(virtqueue_notify);
> +
> +/**
> + * 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).
> + *
> + * Returns false if kick failed, otherwise true.
> + */
> +bool virtqueue_kick(struct virtqueue *vq)
> +{
> + if (virtqueue_kick_prepare(vq))
> + return virtqueue_notify(vq);
> + return true;
> +}
> +EXPORT_SYMBOL_GPL(virtqueue_kick);
> +
> +/**
> + * virtqueue_enable_cb_prepare - restart callbacks after disable_cb
> + * @vq: the struct virtqueue we're talking about.
> + *
> + * This re-enables callbacks; it returns current queue state
> + * in an opaque unsigned value. This value should be later tested by
> + * virtqueue_poll, to detect a possible race between the driver checking for
> + * more work, and enabling callbacks.
> + *
> + * Caller must ensure we don't call this with other virtqueue
> + * operations at the same time (except where noted).
> + */
> +unsigned int virtqueue_enable_cb_prepare(struct virtqueue *vq)
> +{
> + return vq->ops->enable_cb_prepare(vq);
> +}
> +EXPORT_SYMBOL_GPL(virtqueue_enable_cb_prepare);
> +
> +/**
> + * virtqueue_enable_cb - restart callbacks after disable_cb.
> + * @vq: the struct virtqueue we're talking about.
> + *
> + * This re-enables callbacks; it returns "false" if there are pending
> + * buffers in the queue, to detect a possible race between the driver
> + * checking for more work, and enabling callbacks.
> + *
> + * Caller must ensure we don't call this with other virtqueue
> + * operations at the same time (except where noted).
> + */
> +bool virtqueue_enable_cb(struct virtqueue *vq)
> +{
> + unsigned int val = vq->ops->enable_cb_prepare(vq);
> +
> + return !vq->ops->poll(vq, val);
> +}
> +EXPORT_SYMBOL_GPL(virtqueue_enable_cb);
> +
> +/**
> + * virtqueue_enable_cb_delayed - restart callbacks after disable_cb.
> + * @vq: the struct virtqueue we're talking about.
> + *
> + * This re-enables callbacks but hints to the other side to delay
> + * interrupts until most of the available buffers have been processed;
> + * it returns "false" if there are many pending buffers in the queue,
> + * to detect a possible race between the driver checking for more work,
> + * and enabling callbacks.
> + *
> + * Caller must ensure we don't call this with other virtqueue
> + * operations at the same time (except where noted).
> + */
> +bool virtqueue_enable_cb_delayed(struct virtqueue *vq)
> +{
> + return vq->ops->enable_cb_delayed(vq);
> +}
> +EXPORT_SYMBOL_GPL(virtqueue_enable_cb_delayed);
> +
> +/**
> + * virtqueue_disable_cb - disable callbacks
> + * @vq: the struct virtqueue we're talking about.
> + *
> + * Note that this is not necessarily synchronous, hence unreliable and only
> + * useful as an optimization.
> + *
> + * Unlike other operations, this need not be serialized.
> + */
> +void virtqueue_disable_cb(struct virtqueue *vq)
> +{
> + vq->ops->disable_cb(vq);
> +}
> +EXPORT_SYMBOL_GPL(virtqueue_disable_cb);
> +
> +/**
> + * virtqueue_poll - query pending used buffers
> + * @vq: the struct virtqueue we're talking about.
> + * @last_used_idx: virtqueue state (from call to virtqueue_enable_cb_prepare).
> + *
> + * Returns "true" if there are pending used buffers in the queue.
> + *
> + * This does not need to be serialized.
> + */
> +bool virtqueue_poll(struct virtqueue *vq, unsigned int idx)
> +{
> + return vq->ops->poll(vq, idx);
> +}
> +EXPORT_SYMBOL_GPL(virtqueue_poll);
> +
> +/**
> + * virtqueue_get_buf_ctx - get the next used buffer
> + * @vq: the struct virtqueue we're talking about.
> + * @len: the length written into the buffer
> + * @ctx: extra context for the token
> + *
> + * 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 "data" token
> + * handed to virtqueue_add_*().
> + */
> +void *virtqueue_get_buf_ctx(struct virtqueue *vq, unsigned int *len,
> + void **ctx)
> +{
> + return vq->ops->get_buf_ctx(vq, len, ctx);
> +}
> +EXPORT_SYMBOL_GPL(virtqueue_get_buf_ctx);
> +
> +void *virtqueue_get_buf(struct virtqueue *vq, unsigned int *len)
> +{
> + return vq->ops->get_buf_ctx(vq, len, NULL);
> +}
> +EXPORT_SYMBOL_GPL(virtqueue_get_buf);
> +
> +/**
> + * virtqueue_detach_unused_buf - detach first unused buffer
> + * @vq: the struct virtqueue we're talking about.
> + *
> + * Returns NULL or the "data" token handed to virtqueue_add_*().
> + * This is not valid on an active queue; it is useful for device
> + * shutdown or the reset queue.
> + */
> +void *virtqueue_detach_unused_buf(struct virtqueue *vq)
> +{
> + return vq->ops->detach_unused_buf(vq);
> +}
> +EXPORT_SYMBOL_GPL(virtqueue_detach_unused_buf);
> +
> +/**
> + * virtqueue_get_vring_size - return the size of the virtqueue's vring
> + * @vq: the struct virtqueue containing the vring of interest.
> + *
> + * Returns the size of the vring. This is mainly used for boasting to
> + * userspace. Unlike other operations, this need not be serialized.
> + */
> +unsigned int virtqueue_get_vring_size(const struct virtqueue *vq)
> +{
> + return vq->ops->get_vring_size(vq);
> +}
> +EXPORT_SYMBOL_GPL(virtqueue_get_vring_size);
> +
> +/**
> + * virtqueue_resize - resize the vring of vq
> + * @vq: the struct virtqueue we're talking about.
> + * @num: new ring num
> + * @recycle: callback for recycle the useless buffer
> + *
> + * When it is really necessary to create a new vring, it will set the current vq
> + * into the reset state. Then call the passed callback to recycle the buffer
> + * that is no longer used. Only after the new vring is successfully created, the
> + * old vring will be released.
> + *
> + * 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.
> + * 0: success.
> + * -ENOMEM: Failed to allocate a new ring, fall back to the original ring size.
> + * vq can still work normally
> + * -EBUSY: Failed to sync with device, vq may not work properly
> + * -ENOENT: Transport or device not supported
> + * -E2BIG/-EINVAL: num error
> + * -EPERM: Operation not permitted
> + *
> + */
> +int virtqueue_resize(struct virtqueue *vq, u32 num,
> + void (*recycle)(struct virtqueue *vq, void *buf))
> +{
> + if (vq->ops->resize)
> + return vq->ops->resize(vq, num, recycle);
> +
> + return -ENOENT;
> +}
> +EXPORT_SYMBOL_GPL(virtqueue_resize);
> +
> +bool virtqueue_is_broken(const struct virtqueue *vq)
> +{
> + return vq->ops->is_broken(vq);
> +}
> +EXPORT_SYMBOL_GPL(virtqueue_is_broken);
> +
> +/*
> + * This should prevent the device from being used, allowing drivers to
> + * recover. You may need to grab appropriate locks to flush.
> + */
> +void virtio_break_device(struct virtio_device *dev)
> +{
> + struct virtqueue *vq;
> +
> + spin_lock(&dev->vqs_list_lock);
> + list_for_each_entry(vq, &dev->vqs, list) {
> + vq->ops->__break(vq);
> + }
> + spin_unlock(&dev->vqs_list_lock);
> +}
> +EXPORT_SYMBOL_GPL(virtio_break_device);
> +
> +/*
> + * This should allow the device to be used by the driver. You may
> + * need to grab appropriate locks to flush the write to
> + * vq->broken. This should only be used in some specific case e.g
> + * (probing and restoring). This function should only be called by the
> + * core, not directly by the driver.
> + */
> +void __virtio_unbreak_device(struct virtio_device *dev)
> +{
> + struct virtqueue *vq;
> +
> + spin_lock(&dev->vqs_list_lock);
> + list_for_each_entry(vq, &dev->vqs, list) {
> + vq->ops->__unbreak(vq);
> + }
> + spin_unlock(&dev->vqs_list_lock);
> +}
> +EXPORT_SYMBOL_GPL(__virtio_unbreak_device);
> +
> static int virtio_init(void)
> {
> if (bus_register(&virtio_bus) != 0)
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index c5310eaf8b46..7b86417255db 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -227,6 +227,8 @@ static struct virtqueue *__vring_new_virtqueue(unsigned int index,
> static struct vring_desc_extra *vring_alloc_desc_extra(unsigned int num);
> static void vring_free(struct virtqueue *_vq);
>
> +static struct virtqueue_ops vring_ops;
> +
> /*
> * Helpers.
> */
> @@ -2041,6 +2043,7 @@ static struct virtqueue *vring_create_virtqueue_packed(
> vq->vq.name = name;
> vq->vq.index = index;
> vq->vq.reset = false;
> + vq->vq.ops = &vring_ops;
> vq->we_own_ring = true;
> vq->notify = notify;
> vq->weak_barriers = weak_barriers;
> @@ -2114,17 +2117,17 @@ static int virtqueue_resize_packed(struct virtqueue *_vq, u32 num)
>
>
> /*
> - * Generic functions and exported symbols.
> + * Vring specific operation functions
> */
>
> -static inline int virtqueue_add(struct virtqueue *_vq,
> - struct scatterlist *sgs[],
> - unsigned int total_sg,
> - unsigned int out_sgs,
> - unsigned int in_sgs,
> - void *data,
> - void *ctx,
> - gfp_t gfp)
> +static inline int vring_virtqueue_add_sgs(struct virtqueue *_vq,
> + struct scatterlist *sgs[],
> + unsigned int total_sg,
> + unsigned int out_sgs,
> + unsigned int in_sgs,
> + void *data,
> + void *ctx,
> + gfp_t gfp)
> {
> struct vring_virtqueue *vq = to_vvq(_vq);
>
> @@ -2135,110 +2138,7 @@ static inline int virtqueue_add(struct virtqueue *_vq,
> }
>
> /**
> - * virtqueue_add_sgs - 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)
> - * @data: the token identifying the buffer.
> - * @gfp: how to do memory allocations (if necessary).
> - *
> - * 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_sgs(struct virtqueue *_vq,
> - struct scatterlist *sgs[],
> - unsigned int out_sgs,
> - unsigned int in_sgs,
> - void *data,
> - gfp_t gfp)
> -{
> - unsigned int i, total_sg = 0;
> -
> - /* Count them first. */
> - for (i = 0; i < out_sgs + in_sgs; i++) {
> - struct scatterlist *sg;
> -
> - for (sg = sgs[i]; sg; sg = sg_next(sg))
> - total_sg++;
> - }
> - return virtqueue_add(_vq, sgs, total_sg, out_sgs, in_sgs,
> - data, NULL, gfp);
> -}
> -EXPORT_SYMBOL_GPL(virtqueue_add_sgs);
> -
> -/**
> - * virtqueue_add_outbuf - expose output buffers to other end
> - * @vq: the struct virtqueue we're talking about.
> - * @sg: scatterlist (must be well-formed and terminated!)
> - * @num: the number of entries in @sg readable by other side
> - * @data: the token identifying the buffer.
> - * @gfp: how to do memory allocations (if necessary).
> - *
> - * 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_outbuf(struct virtqueue *vq,
> - struct scatterlist *sg, unsigned int num,
> - void *data,
> - gfp_t gfp)
> -{
> - return virtqueue_add(vq, &sg, num, 1, 0, data, NULL, gfp);
> -}
> -EXPORT_SYMBOL_GPL(virtqueue_add_outbuf);
> -
> -/**
> - * virtqueue_add_inbuf - expose input buffers to other end
> - * @vq: the struct virtqueue we're talking about.
> - * @sg: scatterlist (must be well-formed and terminated!)
> - * @num: the number of entries in @sg writable by other side
> - * @data: the token identifying the buffer.
> - * @gfp: how to do memory allocations (if necessary).
> - *
> - * 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_inbuf(struct virtqueue *vq,
> - struct scatterlist *sg, unsigned int num,
> - void *data,
> - gfp_t gfp)
> -{
> - return virtqueue_add(vq, &sg, num, 0, 1, data, NULL, gfp);
> -}
> -EXPORT_SYMBOL_GPL(virtqueue_add_inbuf);
> -
> -/**
> - * virtqueue_add_inbuf_ctx - expose input buffers to other end
> - * @vq: the struct virtqueue we're talking about.
> - * @sg: scatterlist (must be well-formed and terminated!)
> - * @num: the number of entries in @sg writable by other side
> - * @data: the token identifying the buffer.
> - * @ctx: extra context for the token
> - * @gfp: how to do memory allocations (if necessary).
> - *
> - * 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_inbuf_ctx(struct virtqueue *vq,
> - struct scatterlist *sg, unsigned int num,
> - void *data,
> - void *ctx,
> - gfp_t gfp)
> -{
> - return virtqueue_add(vq, &sg, num, 0, 1, data, ctx, gfp);
> -}
> -EXPORT_SYMBOL_GPL(virtqueue_add_inbuf_ctx);
> -
> -/**
> - * virtqueue_kick_prepare - first half of split virtqueue_kick call.
> + * vring_virtqueue_kick_prepare - first half of split virtqueue_kick call.
> * @_vq: the struct virtqueue
> *
> * Instead of virtqueue_kick(), you can do:
> @@ -2248,24 +2148,23 @@ EXPORT_SYMBOL_GPL(virtqueue_add_inbuf_ctx);
> * This is sometimes useful because the virtqueue_kick_prepare() needs
> * to be serialized, but the actual virtqueue_notify() call does not.
> */
> -bool virtqueue_kick_prepare(struct virtqueue *_vq)
> +static bool vring_virtqueue_kick_prepare(struct virtqueue *_vq)
> {
> struct vring_virtqueue *vq = to_vvq(_vq);
>
> return vq->packed_ring ? virtqueue_kick_prepare_packed(_vq) :
> virtqueue_kick_prepare_split(_vq);
> }
> -EXPORT_SYMBOL_GPL(virtqueue_kick_prepare);
>
> /**
> - * virtqueue_notify - second half of split virtqueue_kick call.
> + * vring_virtqueue_notify - second half of split virtqueue_kick call.
> * @_vq: the struct virtqueue
> *
> * This does not need to be serialized.
> *
> * Returns false if host notify failed or queue is broken, otherwise true.
> */
> -bool virtqueue_notify(struct virtqueue *_vq)
> +static bool vring_virtqueue_notify(struct virtqueue *_vq)
> {
> struct vring_virtqueue *vq = to_vvq(_vq);
>
> @@ -2279,30 +2178,9 @@ bool virtqueue_notify(struct virtqueue *_vq)
> }
> return true;
> }
> -EXPORT_SYMBOL_GPL(virtqueue_notify);
>
> /**
> - * 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).
> - *
> - * Returns false if kick failed, otherwise true.
> - */
> -bool virtqueue_kick(struct virtqueue *vq)
> -{
> - if (virtqueue_kick_prepare(vq))
> - return virtqueue_notify(vq);
> - return true;
> -}
> -EXPORT_SYMBOL_GPL(virtqueue_kick);
> -
> -/**
> - * virtqueue_get_buf_ctx - get the next used buffer
> + * vring_virtqueue_get_buf_ctx - get the next used buffer
> * @_vq: the struct virtqueue we're talking about.
> * @len: the length written into the buffer
> * @ctx: extra context for the token
> @@ -2318,7 +2196,7 @@ EXPORT_SYMBOL_GPL(virtqueue_kick);
> * Returns NULL if there are no used buffers, or the "data" token
> * handed to virtqueue_add_*().
> */
> -void *virtqueue_get_buf_ctx(struct virtqueue *_vq, unsigned int *len,
> +static void *vring_virtqueue_get_buf_ctx(struct virtqueue *_vq, unsigned int *len,
> void **ctx)
> {
> struct vring_virtqueue *vq = to_vvq(_vq);
> @@ -2326,15 +2204,9 @@ void *virtqueue_get_buf_ctx(struct virtqueue *_vq, unsigned int *len,
> return vq->packed_ring ? virtqueue_get_buf_ctx_packed(_vq, len, ctx) :
> virtqueue_get_buf_ctx_split(_vq, len, ctx);
> }
> -EXPORT_SYMBOL_GPL(virtqueue_get_buf_ctx);
>
> -void *virtqueue_get_buf(struct virtqueue *_vq, unsigned int *len)
> -{
> - return virtqueue_get_buf_ctx(_vq, len, NULL);
> -}
> -EXPORT_SYMBOL_GPL(virtqueue_get_buf);
> /**
> - * virtqueue_disable_cb - disable callbacks
> + * vring_virtqueue_disable_cb - disable callbacks
> * @_vq: the struct virtqueue we're talking about.
> *
> * Note that this is not necessarily synchronous, hence unreliable and only
> @@ -2342,7 +2214,7 @@ EXPORT_SYMBOL_GPL(virtqueue_get_buf);
> *
> * Unlike other operations, this need not be serialized.
> */
> -void virtqueue_disable_cb(struct virtqueue *_vq)
> +static void vring_virtqueue_disable_cb(struct virtqueue *_vq)
> {
> struct vring_virtqueue *vq = to_vvq(_vq);
>
> @@ -2351,10 +2223,9 @@ void virtqueue_disable_cb(struct virtqueue *_vq)
> else
> virtqueue_disable_cb_split(_vq);
> }
> -EXPORT_SYMBOL_GPL(virtqueue_disable_cb);
>
> /**
> - * virtqueue_enable_cb_prepare - restart callbacks after disable_cb
> + * vring_virtqueue_enable_cb_prepare - restart callbacks after disable_cb
> * @_vq: the struct virtqueue we're talking about.
> *
> * This re-enables callbacks; it returns current queue state
> @@ -2365,7 +2236,7 @@ EXPORT_SYMBOL_GPL(virtqueue_disable_cb);
> * Caller must ensure we don't call this with other virtqueue
> * operations at the same time (except where noted).
> */
> -unsigned int virtqueue_enable_cb_prepare(struct virtqueue *_vq)
> +static unsigned int vring_virtqueue_enable_cb_prepare(struct virtqueue *_vq)
> {
> struct vring_virtqueue *vq = to_vvq(_vq);
>
> @@ -2375,10 +2246,9 @@ unsigned int virtqueue_enable_cb_prepare(struct virtqueue *_vq)
> return vq->packed_ring ? virtqueue_enable_cb_prepare_packed(_vq) :
> virtqueue_enable_cb_prepare_split(_vq);
> }
> -EXPORT_SYMBOL_GPL(virtqueue_enable_cb_prepare);
>
> /**
> - * virtqueue_poll - query pending used buffers
> + * vring_virtqueue_poll - query pending used buffers
> * @_vq: the struct virtqueue we're talking about.
> * @last_used_idx: virtqueue state (from call to virtqueue_enable_cb_prepare).
> *
> @@ -2386,7 +2256,7 @@ EXPORT_SYMBOL_GPL(virtqueue_enable_cb_prepare);
> *
> * This does not need to be serialized.
> */
> -bool virtqueue_poll(struct virtqueue *_vq, unsigned int last_used_idx)
> +static bool vring_virtqueue_poll(struct virtqueue *_vq, unsigned int last_used_idx)
> {
> struct vring_virtqueue *vq = to_vvq(_vq);
>
> @@ -2397,29 +2267,9 @@ bool virtqueue_poll(struct virtqueue *_vq, unsigned int last_used_idx)
> return vq->packed_ring ? virtqueue_poll_packed(_vq, last_used_idx) :
> virtqueue_poll_split(_vq, last_used_idx);
> }
> -EXPORT_SYMBOL_GPL(virtqueue_poll);
>
> /**
> - * virtqueue_enable_cb - restart callbacks after disable_cb.
> - * @_vq: the struct virtqueue we're talking about.
> - *
> - * This re-enables callbacks; it returns "false" if there are pending
> - * buffers in the queue, to detect a possible race between the driver
> - * checking for more work, and enabling callbacks.
> - *
> - * Caller must ensure we don't call this with other virtqueue
> - * operations at the same time (except where noted).
> - */
> -bool virtqueue_enable_cb(struct virtqueue *_vq)
> -{
> - unsigned int last_used_idx = virtqueue_enable_cb_prepare(_vq);
> -
> - return !virtqueue_poll(_vq, last_used_idx);
> -}
> -EXPORT_SYMBOL_GPL(virtqueue_enable_cb);
> -
> -/**
> - * virtqueue_enable_cb_delayed - restart callbacks after disable_cb.
> + * vring_virtqueue_enable_cb_delayed - restart callbacks after disable_cb.
> * @_vq: the struct virtqueue we're talking about.
> *
> * This re-enables callbacks but hints to the other side to delay
> @@ -2431,7 +2281,7 @@ EXPORT_SYMBOL_GPL(virtqueue_enable_cb);
> * Caller must ensure we don't call this with other virtqueue
> * operations at the same time (except where noted).
> */
> -bool virtqueue_enable_cb_delayed(struct virtqueue *_vq)
> +static bool vring_virtqueue_enable_cb_delayed(struct virtqueue *_vq)
> {
> struct vring_virtqueue *vq = to_vvq(_vq);
>
> @@ -2441,24 +2291,22 @@ bool virtqueue_enable_cb_delayed(struct virtqueue *_vq)
> return vq->packed_ring ? virtqueue_enable_cb_delayed_packed(_vq) :
> virtqueue_enable_cb_delayed_split(_vq);
> }
> -EXPORT_SYMBOL_GPL(virtqueue_enable_cb_delayed);
>
> /**
> - * virtqueue_detach_unused_buf - detach first unused buffer
> + * vring_virtqueue_detach_unused_buf - detach first unused buffer
> * @_vq: the struct virtqueue we're talking about.
> *
> * Returns NULL or the "data" token handed to virtqueue_add_*().
> * This is not valid on an active queue; it is useful for device
> * shutdown or the reset queue.
> */
> -void *virtqueue_detach_unused_buf(struct virtqueue *_vq)
> +static void *vring_virtqueue_detach_unused_buf(struct virtqueue *_vq)
> {
> struct vring_virtqueue *vq = to_vvq(_vq);
>
> return vq->packed_ring ? virtqueue_detach_unused_buf_packed(_vq) :
> virtqueue_detach_unused_buf_split(_vq);
> }
> -EXPORT_SYMBOL_GPL(virtqueue_detach_unused_buf);
>
> static inline bool more_used(const struct vring_virtqueue *vq)
> {
> @@ -2531,6 +2379,7 @@ static struct virtqueue *__vring_new_virtqueue(unsigned int index,
> vq->vq.name = name;
> vq->vq.index = index;
> vq->vq.reset = false;
> + vq->vq.ops = &vring_ops;
> vq->we_own_ring = false;
> vq->notify = notify;
> vq->weak_barriers = weak_barriers;
> @@ -2616,7 +2465,7 @@ struct virtqueue *vring_create_virtqueue_dma(
> EXPORT_SYMBOL_GPL(vring_create_virtqueue_dma);
>
> /**
> - * virtqueue_resize - resize the vring of vq
> + * vring_virtqueue_resize - resize the vring of vq
> * @_vq: the struct virtqueue we're talking about.
> * @num: new ring num
> * @recycle: callback for recycle the useless buffer
> @@ -2639,8 +2488,8 @@ EXPORT_SYMBOL_GPL(vring_create_virtqueue_dma);
> * -EPERM: Operation not permitted
> *
> */
> -int virtqueue_resize(struct virtqueue *_vq, u32 num,
> - void (*recycle)(struct virtqueue *vq, void *buf))
> +static int vring_virtqueue_resize(struct virtqueue *_vq, u32 num,
> + void (*recycle)(struct virtqueue *vq, void *buf))
> {
> struct vring_virtqueue *vq = to_vvq(_vq);
> struct virtio_device *vdev = vq->vq.vdev;
> @@ -2669,7 +2518,7 @@ int virtqueue_resize(struct virtqueue *_vq, u32 num,
> if (err)
> return err;
>
> - while ((buf = virtqueue_detach_unused_buf(_vq)) != NULL)
> + while ((buf = vring_virtqueue_detach_unused_buf(_vq)) != NULL)
> recycle(_vq, buf);
>
> if (vq->packed_ring)
> @@ -2682,7 +2531,6 @@ int virtqueue_resize(struct virtqueue *_vq, u32 num,
>
> return err;
> }
> -EXPORT_SYMBOL_GPL(virtqueue_resize);
>
> /* Only available for split ring */
> struct virtqueue *vring_new_virtqueue(unsigned int index,
> @@ -2809,20 +2657,19 @@ void vring_transport_features(struct virtio_device *vdev)
> EXPORT_SYMBOL_GPL(vring_transport_features);
>
> /**
> - * virtqueue_get_vring_size - return the size of the virtqueue's vring
> + * vring_virtqueue_get_vring_size - return the size of the virtqueue's vring
> * @_vq: the struct virtqueue containing the vring of interest.
> *
> * Returns the size of the vring. This is mainly used for boasting to
> * userspace. Unlike other operations, this need not be serialized.
> */
> -unsigned int virtqueue_get_vring_size(const struct virtqueue *_vq)
> +static unsigned int vring_virtqueue_get_vring_size(const struct virtqueue *_vq)
> {
>
> const struct vring_virtqueue *vq = to_vvq(_vq);
>
> return vq->packed_ring ? vq->packed.vring.num : vq->split.vring.num;
> }
> -EXPORT_SYMBOL_GPL(virtqueue_get_vring_size);
>
> /*
> * This function should only be called by the core, not directly by the driver.
> @@ -2848,54 +2695,29 @@ void __virtqueue_unbreak(struct virtqueue *_vq)
> }
> EXPORT_SYMBOL_GPL(__virtqueue_unbreak);
>
> -bool virtqueue_is_broken(const struct virtqueue *_vq)
> +static bool vring_virtqueue_is_broken(const struct virtqueue *_vq)
> {
> const struct vring_virtqueue *vq = to_vvq(_vq);
>
> return READ_ONCE(vq->broken);
> }
> -EXPORT_SYMBOL_GPL(virtqueue_is_broken);
> -
> -/*
> - * This should prevent the device from being used, allowing drivers to
> - * recover. You may need to grab appropriate locks to flush.
> - */
> -void virtio_break_device(struct virtio_device *dev)
> -{
> - struct virtqueue *_vq;
> -
> - spin_lock(&dev->vqs_list_lock);
> - list_for_each_entry(_vq, &dev->vqs, list) {
> - struct vring_virtqueue *vq = to_vvq(_vq);
> -
> - /* Pairs with READ_ONCE() in virtqueue_is_broken(). */
> - WRITE_ONCE(vq->broken, true);
> - }
> - spin_unlock(&dev->vqs_list_lock);
> -}
> -EXPORT_SYMBOL_GPL(virtio_break_device);
> -
> -/*
> - * This should allow the device to be used by the driver. You may
> - * need to grab appropriate locks to flush the write to
> - * vq->broken. This should only be used in some specific case e.g
> - * (probing and restoring). This function should only be called by the
> - * core, not directly by the driver.
> - */
> -void __virtio_unbreak_device(struct virtio_device *dev)
> -{
> - struct virtqueue *_vq;
> -
> - spin_lock(&dev->vqs_list_lock);
> - list_for_each_entry(_vq, &dev->vqs, list) {
> - struct vring_virtqueue *vq = to_vvq(_vq);
>
> - /* Pairs with READ_ONCE() in virtqueue_is_broken(). */
> - WRITE_ONCE(vq->broken, false);
> - }
> - spin_unlock(&dev->vqs_list_lock);
> -}
> -EXPORT_SYMBOL_GPL(__virtio_unbreak_device);
> +static struct virtqueue_ops vring_ops = {
> + .add_sgs = vring_virtqueue_add_sgs,
> + .kick_prepare = vring_virtqueue_kick_prepare,
> + .notify = vring_virtqueue_notify,
> + .enable_cb_prepare = vring_virtqueue_enable_cb_prepare,
> + .enable_cb_delayed = vring_virtqueue_enable_cb_delayed,
> + .disable_cb = vring_virtqueue_disable_cb,
> + .poll = vring_virtqueue_poll,
> + .get_buf_ctx = vring_virtqueue_get_buf_ctx,
> + .detach_unused_buf = vring_virtqueue_detach_unused_buf,
> + .get_vring_size = vring_virtqueue_get_vring_size,
> + .resize = vring_virtqueue_resize,
> + .__break = __virtqueue_break,
> + .__unbreak = __virtqueue_unbreak,
> + .is_broken = vring_virtqueue_is_broken,
> +};
>
> dma_addr_t virtqueue_get_desc_addr(const struct virtqueue *_vq)
> {
> diff --git a/include/linux/virtio.h b/include/linux/virtio.h
> index b93238db94e3..845858b8761e 100644
> --- a/include/linux/virtio.h
> +++ b/include/linux/virtio.h
> @@ -10,6 +10,34 @@
> #include <linux/mod_devicetable.h>
> #include <linux/gfp.h>
>
> +struct virtqueue;
> +
> +/**
> + * struct virtqueue_ops - abstract operations for a virtqueue.
> + *
> + * Descriptions of each field see the comments in virtio.c
> + */
> +struct virtqueue_ops {
> + int (*add_sgs)(struct virtqueue *vq, struct scatterlist *sgs[],
> + unsigned int total_sg,
> + unsigned int out_sgs, unsigned int in_sgs,
> + void *data, void *ctx, gfp_t gfp);
> + bool (*kick_prepare)(struct virtqueue *vq);
> + bool (*notify)(struct virtqueue *vq);
> + unsigned int (*enable_cb_prepare)(struct virtqueue *vq);
> + bool (*enable_cb_delayed)(struct virtqueue *vq);
> + void (*disable_cb)(struct virtqueue *vq);
> + bool (*poll)(struct virtqueue *vq, unsigned int idx);
> + void *(*get_buf_ctx)(struct virtqueue *vq, unsigned int *len, void **ctx);
> + void *(*detach_unused_buf)(struct virtqueue *vq);
> + unsigned int (*get_vring_size)(const struct virtqueue *vq);
> + int (*resize)(struct virtqueue *vq, u32 num,
> + void (*recycle)(struct virtqueue *vq, void *buf));
> + void (*__break)(struct virtqueue *vq);
> + void (*__unbreak)(struct virtqueue *vq);
> + bool (*is_broken)(const struct virtqueue *vq);
> +};
> +
> /**
> * struct virtqueue - a queue to register buffers for sending or receiving.
> * @list: the chain of virtqueues for this device
> @@ -36,6 +64,7 @@ struct virtqueue {
> unsigned int num_max;
> bool reset;
> void *priv;
> + struct virtqueue_ops *ops;
> };
>
> int virtqueue_add_outbuf(struct virtqueue *vq,
> --
> 2.20.1