[PATCH v2 1/2] virtio: abstract virtqueue related methods

zhenwei pi
2023-05-17T02:56:45Z

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. See changes in virtio.h.

All the vring based virtqueue methods could be abstratct in theory,
MST suggested that add/get bufs and kick functions are quite perfmance
sensitive, so export these functions from virtio_ring.ko, drivers
still call them in a fast path.

Cc: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: zhenwei pi <pizhenwei@bytedance.com>
---
drivers/virtio/virtio_ring.c | 285 +++++-----------------
include/linux/virtio.h | 441 +++++++++++++++++++++++++++++++----
include/linux/virtio_ring.h | 26 +++
3 files changed, 483 insertions(+), 269 deletions(-)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index c5310eaf8b46..82c26f50d941 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -226,6 +226,7 @@ static struct virtqueue *__vring_new_virtqueue(unsigned int index,
struct device *dma_dev);
static struct vring_desc_extra *vring_alloc_desc_extra(unsigned int num);
static void vring_free(struct virtqueue *_vq);
+static void vring_virtqueue_set_ops(struct virtqueue *vq);

/*
* Helpers.
@@ -2036,6 +2037,7 @@ static struct virtqueue *vring_create_virtqueue_packed(
if (!vq)
goto err_vq;

+ vring_virtqueue_set_ops(&vq->vq);
vq->vq.callback = callback;
vq->vq.vdev = vdev;
vq->vq.name = name;
@@ -2117,14 +2119,14 @@ static int virtqueue_resize_packed(struct virtqueue *_vq, u32 num)
* Generic functions and exported symbols.
*/

-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)
+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);

@@ -2133,112 +2135,10 @@ static inline int virtqueue_add(struct virtqueue *_vq,
virtqueue_add_split(_vq, sgs, total_sg,
out_sgs, in_sgs, data, ctx, gfp);
}
+EXPORT_SYMBOL_GPL(vring_virtqueue_add_sgs);

/**
- * 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 +2148,24 @@ 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)
+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);
+EXPORT_SYMBOL_GPL(vring_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)
+bool vring_virtqueue_notify(struct virtqueue *_vq)
{
struct vring_virtqueue *vq = to_vvq(_vq);

@@ -2279,30 +2179,10 @@ bool virtqueue_notify(struct virtqueue *_vq)
}
return true;
}
-EXPORT_SYMBOL_GPL(virtqueue_notify);
+EXPORT_SYMBOL_GPL(vring_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
@@ -2318,23 +2198,17 @@ 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,
- void **ctx)
+void *vring_virtqueue_get_buf_ctx(struct virtqueue *_vq, unsigned int *len, void **ctx)
{
struct vring_virtqueue *vq = to_vvq(_vq);

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);
+EXPORT_SYMBOL_GPL(vring_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 +2216,7 @@ EXPORT_SYMBOL_GPL(virtqueue_get_buf);
*
* Unlike other operations, this need not be serialized.
*/
-void virtqueue_disable_cb(struct virtqueue *_vq)
+void vring_virtqueue_disable_cb(struct virtqueue *_vq)
{
struct vring_virtqueue *vq = to_vvq(_vq);

@@ -2351,10 +2225,10 @@ void virtqueue_disable_cb(struct virtqueue *_vq)
else
virtqueue_disable_cb_split(_vq);
}
-EXPORT_SYMBOL_GPL(virtqueue_disable_cb);
+EXPORT_SYMBOL_GPL(vring_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 +2239,7 @@ 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)
+unsigned int vring_virtqueue_enable_cb_prepare(struct virtqueue *_vq)
{
struct vring_virtqueue *vq = to_vvq(_vq);

@@ -2375,18 +2249,18 @@ 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);
+EXPORT_SYMBOL_GPL(vring_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).
+ * @last_used_idx: virtqueue state (from call to vring_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 last_used_idx)
+bool vring_virtqueue_poll(struct virtqueue *_vq, unsigned int last_used_idx)
{
struct vring_virtqueue *vq = to_vvq(_vq);

@@ -2397,29 +2271,10 @@ 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);
+EXPORT_SYMBOL_GPL(vring_virtqueue_poll);

/**
- * 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 +2286,7 @@ 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)
+bool vring_virtqueue_enable_cb_delayed(struct virtqueue *_vq)
{
struct vring_virtqueue *vq = to_vvq(_vq);

@@ -2441,7 +2296,7 @@ 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);
+EXPORT_SYMBOL_GPL(vring_virtqueue_enable_cb_delayed);

/**
* virtqueue_detach_unused_buf - detach first unused buffer
@@ -2451,14 +2306,13 @@ EXPORT_SYMBOL_GPL(virtqueue_enable_cb_delayed);
* 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)
{
@@ -2525,6 +2379,7 @@ static struct virtqueue *__vring_new_virtqueue(unsigned int index,
if (!vq)
return NULL;

+ vring_virtqueue_set_ops(&vq->vq);
vq->packed_ring = false;
vq->vq.callback = callback;
vq->vq.vdev = vdev;
@@ -2639,8 +2494,8 @@ 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;
@@ -2682,7 +2537,6 @@ 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,
@@ -2815,14 +2669,13 @@ EXPORT_SYMBOL_GPL(vring_transport_features);
* 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.
@@ -2831,7 +2684,7 @@ void __virtqueue_break(struct virtqueue *_vq)
{
struct vring_virtqueue *vq = to_vvq(_vq);

- /* Pairs with READ_ONCE() in virtqueue_is_broken(). */
+ /* Pairs with READ_ONCE() in vring_virtqueue_is_broken(). */
WRITE_ONCE(vq->broken, true);
}
EXPORT_SYMBOL_GPL(__virtqueue_break);
@@ -2843,59 +2696,18 @@ void __virtqueue_unbreak(struct virtqueue *_vq)
{
struct vring_virtqueue *vq = to_vvq(_vq);

- /* Pairs with READ_ONCE() in virtqueue_is_broken(). */
+ /* Pairs with READ_ONCE() in vring_virtqueue_is_broken(). */
WRITE_ONCE(vq->broken, false);
}
EXPORT_SYMBOL_GPL(__virtqueue_unbreak);

-bool virtqueue_is_broken(const struct virtqueue *_vq)
+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);
+EXPORT_SYMBOL_GPL(vring_virtqueue_is_broken);

dma_addr_t virtqueue_get_desc_addr(const struct virtqueue *_vq)
{
@@ -2946,3 +2758,16 @@ const struct vring *virtqueue_get_vring(const struct virtqueue *vq)
EXPORT_SYMBOL_GPL(virtqueue_get_vring);

MODULE_LICENSE("GPL");
+
+static void vring_virtqueue_set_ops(struct virtqueue *vq)
+{
+ /* In theory, add/get bufs and kick functions also could be overwritten,
+ * these functions are quite perfmance sensitive, so call them directly.
+ */
+ vq->abstract = false;
+ vq->detach_unused_buf = vring_virtqueue_detach_unused_buf;
+ vq->get_vring_size = vring_virtqueue_get_vring_size;
+ vq->resize = vring_virtqueue_resize;
+ vq->__break = __virtqueue_break;
+ vq->__unbreak = __virtqueue_unbreak;
+}
diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index b93238db94e3..203f0397dc58 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -9,6 +9,7 @@
#include <linux/device.h>
#include <linux/mod_devicetable.h>
#include <linux/gfp.h>
+#include <linux/virtio_ring.h>

/**
* struct virtqueue - a queue to register buffers for sending or receiving.
@@ -35,67 +36,399 @@ struct virtqueue {
unsigned int num_free;
unsigned int num_max;
bool reset;
+ bool abstract;
void *priv;
+
+ /* abstract operations */
+ 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);
};

-int virtqueue_add_outbuf(struct virtqueue *vq,
- struct scatterlist sg[], unsigned int num,
- void *data,
- gfp_t gfp);
+/**
+ * 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).
+ */
+static inline 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++;
+ }
+
+ if (likely(!vq->abstract))
+ return vring_virtqueue_add_sgs(vq, sgs, total_sg, out_sgs, in_sgs, data, NULL, gfp);
+
+ return vq->add_sgs(vq, sgs, total_sg, out_sgs, in_sgs, data, NULL, gfp);
+}
+
+/**
+ * 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).
+ */
+static inline int virtqueue_add_outbuf(struct virtqueue *vq,
+ struct scatterlist *sg,
+ unsigned int num,
+ void *data,
+ gfp_t gfp)
+{
+ if (likely(!vq->abstract))
+ return vring_virtqueue_add_sgs(vq, &sg, num, 1, 0, data, NULL, gfp);
+
+ return vq->add_sgs(vq, &sg, num, 1, 0, data, NULL, gfp);
+}

-int virtqueue_add_inbuf(struct virtqueue *vq,
- struct scatterlist sg[], unsigned int num,
- void *data,
- gfp_t gfp);
+/**
+ * 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).
+ */
+static inline int virtqueue_add_inbuf(struct virtqueue *vq,
+ struct scatterlist *sg,
+ unsigned int num,
+ void *data,
+ gfp_t gfp)
+{
+ if (likely(!vq->abstract))
+ return vring_virtqueue_add_sgs(vq, &sg, num, 0, 1, data, NULL, gfp);

-int virtqueue_add_inbuf_ctx(struct virtqueue *vq,
- struct scatterlist sg[], unsigned int num,
- void *data,
- void *ctx,
- gfp_t gfp);
+ return vq->add_sgs(vq, &sg, num, 0, 1, data, NULL, gfp);
+}

-int virtqueue_add_sgs(struct virtqueue *vq,
- struct scatterlist *sgs[],
- unsigned int out_sgs,
- unsigned int in_sgs,
- void *data,
- gfp_t gfp);
+/**
+ * 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).
+ */
+static inline int virtqueue_add_inbuf_ctx(struct virtqueue *vq,
+ struct scatterlist *sg,
+ unsigned int num,
+ void *data,
+ void *ctx,
+ gfp_t gfp)
+{
+ if (likely(!vq->abstract))
+ return vring_virtqueue_add_sgs(vq, &sg, num, 0, 1, data, ctx, gfp);

-bool virtqueue_kick(struct virtqueue *vq);
+ return vq->add_sgs(vq, &sg, num, 0, 1, data, ctx, gfp);
+}

-bool virtqueue_kick_prepare(struct virtqueue *vq);
+/**
+ * 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.
+ */
+static inline bool virtqueue_kick_prepare(struct virtqueue *vq)
+{
+ if (likely(!vq->abstract))
+ return vring_virtqueue_kick_prepare(vq);

-bool virtqueue_notify(struct virtqueue *vq);
+ return vq->kick_prepare(vq);
+}

-void *virtqueue_get_buf(struct virtqueue *vq, unsigned int *len);
+/**
+ * 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.
+ */
+static inline bool virtqueue_notify(struct virtqueue *vq)
+{
+ if (likely(!vq->abstract))
+ return vring_virtqueue_notify(vq);

-void *virtqueue_get_buf_ctx(struct virtqueue *vq, unsigned int *len,
- void **ctx);
+ return vq->notify(vq);
+}

-void virtqueue_disable_cb(struct virtqueue *vq);
+/**
+ * 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.
+ */
+static inline bool virtqueue_kick(struct virtqueue *vq)
+{
+ if (virtqueue_kick_prepare(vq))
+ return virtqueue_notify(vq);

-bool virtqueue_enable_cb(struct virtqueue *vq);
+ return true;
+}

-unsigned virtqueue_enable_cb_prepare(struct virtqueue *vq);
+/**
+ * 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).
+ */
+static inline unsigned int virtqueue_enable_cb_prepare(struct virtqueue *vq)
+{
+ if (likely(!vq->abstract))
+ return vring_virtqueue_enable_cb_prepare(vq);

-bool virtqueue_poll(struct virtqueue *vq, unsigned);
+ return vq->enable_cb_prepare(vq);
+}

-bool virtqueue_enable_cb_delayed(struct virtqueue *vq);
+/**
+ * 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.
+ */
+static inline bool virtqueue_poll(struct virtqueue *vq, unsigned int idx)
+{
+ if (likely(!vq->abstract))
+ return vring_virtqueue_poll(vq, idx);

-void *virtqueue_detach_unused_buf(struct virtqueue *vq);
+ return vq->poll(vq, idx);
+}

-unsigned int virtqueue_get_vring_size(const struct virtqueue *vq);
+/**
+ * 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).
+ */
+static inline bool virtqueue_enable_cb(struct virtqueue *vq)
+{
+ unsigned int opaque = virtqueue_enable_cb_prepare(vq);

-bool virtqueue_is_broken(const struct virtqueue *vq);
+ return !virtqueue_poll(vq, opaque);
+}
+
+/**
+ * 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).
+ */
+static inline bool virtqueue_enable_cb_delayed(struct virtqueue *vq)
+{
+ if (likely(!vq->abstract))
+ return vring_virtqueue_enable_cb_delayed(vq);
+
+ return vq->enable_cb_delayed(vq);
+}
+
+/**
+ * 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.
+ */
+static inline void virtqueue_disable_cb(struct virtqueue *vq)
+{
+ if (likely(!vq->abstract)) {
+ vring_virtqueue_disable_cb(vq);
+ return;
+ }
+
+ vq->disable_cb(vq);
+}
+
+/**
+ * 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_*().
+ */
+static inline void *virtqueue_get_buf_ctx(struct virtqueue *vq,
+ unsigned int *len,
+ void **ctx)
+{
+ if (likely(!vq->abstract))
+ return vring_virtqueue_get_buf_ctx(vq, len, ctx);
+
+ return vq->get_buf_ctx(vq, len, ctx);
+}
+
+static inline void *virtqueue_get_buf(struct virtqueue *vq, unsigned int *len)
+{
+ if (likely(!vq->abstract))
+ return vring_virtqueue_get_buf_ctx(vq, len, NULL);
+
+ return vq->get_buf_ctx(vq, len, NULL);
+}
+
+/**
+ * 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.
+ */
+static inline void *virtqueue_detach_unused_buf(struct virtqueue *vq)
+{
+ return vq->detach_unused_buf(vq);
+}
+
+/**
+ * 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.
+ */
+static inline unsigned int virtqueue_get_vring_size(const struct virtqueue *vq)
+{
+ return vq->get_vring_size(vq);
+}
+
+/**
+ * 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
+ *
+ */
+static inline int virtqueue_resize(struct virtqueue *vq, u32 num,
+ void (*recycle)(struct virtqueue *vq, void *buf))
+{
+ if (vq->resize)
+ return vq->resize(vq, num, recycle);
+
+ return -ENOENT;
+}
+
+static inline bool virtqueue_is_broken(const struct virtqueue *vq)
+{
+ if (likely(!vq->abstract))
+ return vring_virtqueue_is_broken(vq);
+
+ return vq->is_broken(vq);
+}

const struct vring *virtqueue_get_vring(const struct virtqueue *vq);
dma_addr_t virtqueue_get_desc_addr(const struct virtqueue *vq);
dma_addr_t virtqueue_get_avail_addr(const struct virtqueue *vq);
dma_addr_t virtqueue_get_used_addr(const struct virtqueue *vq);

-int virtqueue_resize(struct virtqueue *vq, u32 num,
- void (*recycle)(struct virtqueue *vq, void *buf));
-
/**
* struct virtio_device - representation of a device using virtio
* @index: unique position on the virtio bus
@@ -134,9 +467,6 @@ int register_virtio_device(struct virtio_device *dev);
void unregister_virtio_device(struct virtio_device *dev);
bool is_virtio_device(struct device *dev);

-void virtio_break_device(struct virtio_device *dev);
-void __virtio_unbreak_device(struct virtio_device *dev);
-
void __virtqueue_break(struct virtqueue *_vq);
void __virtqueue_unbreak(struct virtqueue *_vq);

@@ -149,6 +479,39 @@ void virtio_reset_device(struct virtio_device *dev);

size_t virtio_max_dma_size(const struct virtio_device *vdev);

+/*
+ * This should prevent the device from being used, allowing drivers to
+ * recover. You may need to grab appropriate locks to flush.
+ */
+static inline 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->__break(vq);
+ }
+ spin_unlock(&dev->vqs_list_lock);
+}
+
+/*
+ * 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.
+ */
+static inline 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->__unbreak(vq);
+ }
+ spin_unlock(&dev->vqs_list_lock);
+}
+
#define virtio_device_for_each_vq(vdev, vq) \
list_for_each_entry(vq, &vdev->vqs, list)

diff --git a/include/linux/virtio_ring.h b/include/linux/virtio_ring.h
index 9b33df741b63..3cfbc98ab3c6 100644
--- a/include/linux/virtio_ring.h
+++ b/include/linux/virtio_ring.h
@@ -4,6 +4,7 @@

#include <asm/barrier.h>
#include <linux/irqreturn.h>
+#include <linux/scatterlist.h>
#include <uapi/linux/virtio_ring.h>

/*
@@ -108,6 +109,31 @@ struct virtqueue *vring_new_virtqueue(unsigned int index,
void (*callback)(struct virtqueue *vq),
const char *name);

+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);
+
+bool vring_virtqueue_kick_prepare(struct virtqueue *vq);
+
+bool vring_virtqueue_notify(struct virtqueue *vq);
+
+void *vring_virtqueue_get_buf_ctx(struct virtqueue *vq, unsigned int *len, void **ctx);
+
+void vring_virtqueue_disable_cb(struct virtqueue *vq);
+
+unsigned vring_virtqueue_enable_cb_prepare(struct virtqueue *vq);
+
+bool vring_virtqueue_poll(struct virtqueue *vq, unsigned);
+
+bool vring_virtqueue_enable_cb_delayed(struct virtqueue *vq);
+
+bool vring_virtqueue_is_broken(const struct virtqueue *vq);
+
/*
* Destroys a virtqueue. If created with vring_create_virtqueue, this
* also frees the ring.
--
2.20.1