Re: [PATCH v7 3/3] vhost: add an RPMsg API

[Mathieu Poirier <mathieu.poirier@linaro.org>]

On Fri, Sep 18, 2020 at 11:02:29AM +0200, Guennadi Liakhovetski wrote:
> Hi Mathieu,
> 
> On Thu, Sep 17, 2020 at 04:01:38PM -0600, Mathieu Poirier wrote:
> > On Thu, Sep 10, 2020 at 01:13:51PM +0200, Guennadi Liakhovetski wrote:
> > > Linux supports running the RPMsg protocol over the VirtIO transport
> > > protocol, but currently there is only support for VirtIO clients and
> > > no support for VirtIO servers. This patch adds a vhost-based RPMsg
> > > server implementation, which makes it possible to use RPMsg over
> > > VirtIO between guest VMs and the host.
> > 
> > I now get the client/server concept you are describing above but that happened
> > only after a lot of mental gymnastics.  If you drop the whole client/server
> > concept and concentrate on what this patch does, things will go better.  I would
> > personally go with what you have in the Kconfig: 
> > 
> > > +	  Vhost RPMsg API allows vhost drivers to communicate with VirtIO
> > > +	  drivers on guest VMs, using the RPMsg over VirtIO protocol.
> > 
> > It is concise but describes exactly what this patch provide.
> 
> Ok, thanks, will try to improve.
> 
> > > Signed-off-by: Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>
> > > ---
> > >  drivers/vhost/Kconfig       |   7 +
> > >  drivers/vhost/Makefile      |   3 +
> > >  drivers/vhost/rpmsg.c       | 370 ++++++++++++++++++++++++++++++++++++
> > >  drivers/vhost/vhost_rpmsg.h |  74 ++++++++
> > >  4 files changed, 454 insertions(+)
> > >  create mode 100644 drivers/vhost/rpmsg.c
> > >  create mode 100644 drivers/vhost/vhost_rpmsg.h
> > > 
> > > diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig
> > > index 587fbae06182..ee1a19b7ab3d 100644
> > > --- a/drivers/vhost/Kconfig
> > > +++ b/drivers/vhost/Kconfig
> > > @@ -38,6 +38,13 @@ config VHOST_NET
> > >  	  To compile this driver as a module, choose M here: the module will
> > >  	  be called vhost_net.
> > >  
> > > +config VHOST_RPMSG
> > > +	tristate
> > > +	select VHOST
> > > +	help
> > > +	  Vhost RPMsg API allows vhost drivers to communicate with VirtIO
> > > +	  drivers on guest VMs, using the RPMsg over VirtIO protocol.
> > > +
> > 
> > I suppose you intend this to be selectable from another config option?
> 
> yes.
> 
> > >  config VHOST_SCSI
> > >  	tristate "VHOST_SCSI TCM fabric driver"
> > >  	depends on TARGET_CORE && EVENTFD
> > > diff --git a/drivers/vhost/Makefile b/drivers/vhost/Makefile
> > > index f3e1897cce85..9cf459d59f97 100644
> > > --- a/drivers/vhost/Makefile
> > > +++ b/drivers/vhost/Makefile
> > > @@ -2,6 +2,9 @@
> > >  obj-$(CONFIG_VHOST_NET) += vhost_net.o
> > >  vhost_net-y := net.o
> > >  
> > > +obj-$(CONFIG_VHOST_RPMSG) += vhost_rpmsg.o
> > > +vhost_rpmsg-y := rpmsg.o
> > > +
> > >  obj-$(CONFIG_VHOST_SCSI) += vhost_scsi.o
> > >  vhost_scsi-y := scsi.o
> > >  
> > > diff --git a/drivers/vhost/rpmsg.c b/drivers/vhost/rpmsg.c
> > > new file mode 100644
> > > index 000000000000..0ddee5b5f017
> > > --- /dev/null
> > > +++ b/drivers/vhost/rpmsg.c
> > > @@ -0,0 +1,370 @@
> > > +// SPDX-License-Identifier: GPL-2.0-only
> > > +/*
> > > + * Copyright(c) 2020 Intel Corporation. All rights reserved.
> > > + *
> > > + * Author: Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>
> > > + *
> > > + * Vhost RPMsg VirtIO interface provides a set of functions to be used on the
> > > + * host side as a counterpart to the guest side RPMsg VirtIO API, provided by
> > > + * drivers/rpmsg/virtio_rpmsg_bus.c. This API can be used by any vhost driver to
> > > + * handle RPMsg specific virtqueue processing.
> > > + * Vhost drivers, using this API will use their own VirtIO device IDs, that
> > > + * should then also be added to the ID table in virtio_rpmsg_bus.c
> > > + */
> > > +
> > > +#include <linux/compat.h>
> > > +#include <linux/file.h>
> > > +#include <linux/miscdevice.h>
> > 
> > As far as I can tell the above two are not needed.
> 
> Look like left-over, will remove.
> 
> > > +#include <linux/module.h>
> > > +#include <linux/mutex.h>
> > > +#include <linux/rpmsg/virtio.h>
> > > +#include <linux/vhost.h>
> > > +#include <uapi/linux/rpmsg.h>
> > > +
> > > +#include "vhost.h"
> > > +#include "vhost_rpmsg.h"
> > > +
> > > +/*
> > > + * All virtio-rpmsg virtual queue kicks always come with just one buffer -
> > > + * either input or output, but we can also handle split messages
> > > + */
> > > +static int vhost_rpmsg_get_msg(struct vhost_virtqueue *vq, unsigned int *cnt)
> > > +{
> > > +	struct vhost_rpmsg *vr = container_of(vq->dev, struct vhost_rpmsg, dev);
> > > +	unsigned int out, in;
> > > +	int head = vhost_get_vq_desc(vq, vq->iov, ARRAY_SIZE(vq->iov), &out, &in,
> > > +				     NULL, NULL);
> > > +	if (head < 0) {
> > > +		vq_err(vq, "%s(): error %d getting buffer\n",
> > > +		       __func__, head);
> > > +		return head;
> > > +	}
> > > +
> > > +	/* Nothing new? */
> > > +	if (head == vq->num)
> > > +		return head;
> > > +
> > > +	if (vq == &vr->vq[VIRTIO_RPMSG_RESPONSE]) {
> > > +		if (out) {
> > > +			vq_err(vq, "%s(): invalid %d output in response queue\n",
> > > +			       __func__, out);
> > > +			goto return_buf;
> > > +		}
> > > +
> > > +		*cnt = in;
> > > +	}
> > > +
> > > +	if (vq == &vr->vq[VIRTIO_RPMSG_REQUEST]) {
> > > +		if (in) {
> > > +			vq_err(vq, "%s(): invalid %d input in request queue\n",
> > > +		       __func__, in);
> > > +			goto return_buf;
> > > +		}
> > > +
> > > +		*cnt = out;
> > > +	}
> > > +
> > > +	return head;
> > > +
> > > +return_buf:
> > > +	vhost_add_used(vq, head, 0);
> > > +
> > > +	return -EINVAL;
> > > +}
> > > +
> > > +static const struct vhost_rpmsg_ept *vhost_rpmsg_ept_find(struct vhost_rpmsg *vr, int addr)
> > > +{
> > > +	unsigned int i;
> > > +
> > > +	for (i = 0; i < vr->n_epts; i++)
> > > +		if (vr->ept[i].addr == addr)
> > > +			return vr->ept + i;
> > > +
> > > +	return NULL;
> > > +}
> > > +
> > > +/*
> > > + * if len < 0, then for reading a request, the complete virtual queue buffer
> > > + * size is prepared, for sending a response, the length in the iterator is used
> > > + */
> > > +int vhost_rpmsg_start_lock(struct vhost_rpmsg *vr, struct vhost_rpmsg_iter *iter,
> > > +			   unsigned int qid, ssize_t len)
> > > +	__acquires(vq->mutex)
> > > +{
> > > +	struct vhost_virtqueue *vq = vr->vq + qid;
> > > +	unsigned int cnt;
> > > +	ssize_t ret;
> > > +	size_t tmp;
> > > +
> > > +	if (qid >= VIRTIO_RPMSG_NUM_OF_VQS)
> > > +		return -EINVAL;
> > > +
> > > +	iter->vq = vq;
> > > +
> > > +	mutex_lock(&vq->mutex);
> > > +	vhost_disable_notify(&vr->dev, vq);
> > > +
> > > +	iter->head = vhost_rpmsg_get_msg(vq, &cnt);
> > > +	if (iter->head == vq->num)
> > > +		iter->head = -EAGAIN;
> > > +
> > > +	if (iter->head < 0) {
> > > +		ret = iter->head;
> > > +		goto unlock;
> > > +	}
> > > +
> > > +	tmp = iov_length(vq->iov, cnt);
> > > +	if (tmp < sizeof(iter->rhdr)) {
> > > +		vq_err(vq, "%s(): size %zu too small\n", __func__, tmp);
> > > +		ret = -ENOBUFS;
> > > +		goto return_buf;
> > > +	}
> > > +
> > > +	switch (qid) {
> > > +	case VIRTIO_RPMSG_REQUEST:
> > > +		if (len >= 0) {
> > > +			if (tmp < sizeof(iter->rhdr) + len) {
> > > +				ret = -ENOBUFS;
> > > +				goto return_buf;
> > > +			}
> > > +
> > > +			tmp = len + sizeof(iter->rhdr);
> > > +		}
> > > +
> > > +		/* len is now the size of the payload */
> > > +		iov_iter_init(&iter->iov_iter, WRITE, vq->iov, cnt, tmp);
> > > +
> > > +		/* Read the RPMSG header with endpoint addresses */
> > > +		tmp = copy_from_iter(&iter->rhdr, sizeof(iter->rhdr), &iter->iov_iter);
> > > +		if (tmp != sizeof(iter->rhdr)) {
> > > +			vq_err(vq, "%s(): got %zu instead of %zu\n", __func__,
> > > +			       tmp, sizeof(iter->rhdr));
> > > +			ret = -EIO;
> > > +			goto return_buf;
> > > +		}
> > > +
> > > +		iter->ept = vhost_rpmsg_ept_find(vr, vhost32_to_cpu(vq, iter->rhdr.dst));
> > > +		if (!iter->ept) {
> > > +			vq_err(vq, "%s(): no endpoint with address %d\n",
> > > +			       __func__, vhost32_to_cpu(vq, iter->rhdr.dst));
> > > +			ret = -ENOENT;
> > > +			goto return_buf;
> > > +		}
> > > +
> > > +		/* Let the endpoint read the payload */
> > > +		if (iter->ept->read) {
> > > +			ret = iter->ept->read(vr, iter);
> > > +			if (ret < 0)
> > > +				goto return_buf;
> > > +
> > > +			iter->rhdr.len = cpu_to_vhost16(vq, ret);
> > > +		} else {
> > > +			iter->rhdr.len = 0;
> > > +		}
> > > +
> > > +		/* Prepare for the response phase */
> > > +		iter->rhdr.dst = iter->rhdr.src;
> > > +		iter->rhdr.src = cpu_to_vhost32(vq, iter->ept->addr);
> > 
> > I'm a little puzzled here - what will the response look like?  And why is it
> > prepared here?  From what I can see doing so introduces coupling with function
> > handle_rpmsg_req_single().  I think confirmation of reception should be handled
> > by endpoints rather than in the core. 
> 
> RPMsg always contain a header, so we keep the header in the iterator. If the 
> caller wants to reply to the request, the easiest way to do that is to reuse the 
> iterator. In that case obviously you have to swap source and destination 
> addresses. This can be done either in the request handler of the API, or by the 
> caller, or in the API response handler. It would be silly to have the user do 
> that, that would be repeated code. But I agree, it's a bit unclean to modify the 
> header before returning it to the user, without knowing, whether the user will 
> use it, in which case it might be surprised to see most fields from the request 
> unchanged and only addresses swapped. I'll move this to response with a check 
> for a reused iterator.
> 
> > > +
> > > +		break;
> > > +	case VIRTIO_RPMSG_RESPONSE:
> > > +		if (!iter->ept && iter->rhdr.dst != cpu_to_vhost32(vq, RPMSG_NS_ADDR)) {
> > > +			/*
> > > +			 * Usually the iterator is configured when processing a
> > > +			 * message on the request queue, but it's also possible
> > > +			 * to send a message on the response queue without a
> > > +			 * preceding request, in that case the iterator must
> > > +			 * contain source and destination addresses.
> > > +			 */
> > > +			iter->ept = vhost_rpmsg_ept_find(vr, vhost32_to_cpu(vq, iter->rhdr.src));
> > > +			if (!iter->ept) {
> > > +				ret = -ENOENT;
> > > +				goto return_buf;
> > > +			}
> > > +		}
> > > +
> > > +		if (len >= 0) {
> > > +			if (tmp < sizeof(iter->rhdr) + len) {
> > > +				ret = -ENOBUFS;
> > > +				goto return_buf;
> > > +			}
> > > +
> > > +			iter->rhdr.len = cpu_to_vhost16(vq, len);
> > > +			tmp = len + sizeof(iter->rhdr);
> > > +		}
> > > +
> > > +		/* len is now the size of the payload */
> > > +		iov_iter_init(&iter->iov_iter, READ, vq->iov, cnt, tmp);
> > > +
> > > +		/* Write the RPMSG header with endpoint addresses */
> > > +		tmp = copy_to_iter(&iter->rhdr, sizeof(iter->rhdr), &iter->iov_iter);
> > > +		if (tmp != sizeof(iter->rhdr)) {
> > > +			ret = -EIO;
> > > +			goto return_buf;
> > > +		}
> > > +
> > > +		/* Let the endpoint write the payload */
> > 
> > I would specifically mention that namespace payloads are taken care of by
> > vhost_rpmsg_ns_announce().  That makes it easier for people to connect the dots. 
> 
> Ok
> 
> > > +		if (iter->ept && iter->ept->write) {
> > > +			ret = iter->ept->write(vr, iter);
> > > +			if (ret < 0)
> > > +				goto return_buf;
> > > +		}
> > > +
> > > +		break;
> > > +	}
> > > +
> > > +	return 0;
> > > +
> > > +return_buf:
> > > +	vhost_add_used(vq, iter->head, 0);
> > > +unlock:
> > > +	vhost_enable_notify(&vr->dev, vq);
> > > +	mutex_unlock(&vq->mutex);
> > > +
> > > +	return ret;
> > > +}
> > > +EXPORT_SYMBOL_GPL(vhost_rpmsg_start_lock);
> > > +
> > > +size_t vhost_rpmsg_copy(struct vhost_rpmsg *vr, struct vhost_rpmsg_iter *iter,
> > > +			void *data, size_t size)
> > > +{
> > > +	/*
> > > +	 * We could check for excess data, but copy_{to,from}_iter() don't do
> > > +	 * that either
> > > +	 */
> > > +	if (iter->vq == vr->vq + VIRTIO_RPMSG_RESPONSE)
> > > +		return copy_to_iter(data, size, &iter->iov_iter);
> > > +
> > > +	return copy_from_iter(data, size, &iter->iov_iter);
> > > +}
> > > +EXPORT_SYMBOL_GPL(vhost_rpmsg_copy);
> > > +
> > > +int vhost_rpmsg_finish_unlock(struct vhost_rpmsg *vr,
> > > +			      struct vhost_rpmsg_iter *iter)
> > > +	__releases(vq->mutex)
> > > +{
> > > +	if (iter->head >= 0)
> > > +		vhost_add_used_and_signal(iter->vq->dev, iter->vq, iter->head,
> > > +					  vhost16_to_cpu(iter->vq, iter->rhdr.len) +
> > > +					  sizeof(iter->rhdr));
> > > +
> > > +	vhost_enable_notify(&vr->dev, iter->vq);
> > > +	mutex_unlock(&iter->vq->mutex);
> > > +
> > > +	return iter->head;
> > > +}
> > > +EXPORT_SYMBOL_GPL(vhost_rpmsg_finish_unlock);
> > > +
> > > +/*
> > > + * Return false to terminate the external loop only if we fail to obtain either
> > > + * a request or a response buffer
> > > + */
> > > +static bool handle_rpmsg_req_single(struct vhost_rpmsg *vr,
> > > +				    struct vhost_virtqueue *vq)
> > > +{
> > > +	struct vhost_rpmsg_iter iter;
> > > +	int ret = vhost_rpmsg_start_lock(vr, &iter, VIRTIO_RPMSG_REQUEST, -EINVAL);
> > > +	if (!ret)
> > > +		ret = vhost_rpmsg_finish_unlock(vr, &iter);
> > > +	if (ret < 0) {
> > > +		if (ret != -EAGAIN)
> > > +			vq_err(vq, "%s(): RPMSG processing failed %d\n",
> > > +			       __func__, ret);
> > > +		return false;
> > > +	}
> > > +
> > > +	if (!iter.ept->write)
> > > +		return true;
> > > +
> > > +	ret = vhost_rpmsg_start_lock(vr, &iter, VIRTIO_RPMSG_RESPONSE, -EINVAL);
> > > +	if (!ret)
> > > +		ret = vhost_rpmsg_finish_unlock(vr, &iter);
> > > +	if (ret < 0) {
> > > +		vq_err(vq, "%s(): RPMSG finalising failed %d\n", __func__, ret);
> > > +		return false;
> > > +	}
> > 
> > As I said before dealing with the "response" queue here seems to be introducing
> > coupling with vhost_rpmsg_start_lock()...  Endpoints should be doing that.
> 
> Sorry, could you elaborate a bit, what do you mean by coupling?
> 
> > > +
> > > +	return true;
> > > +}
> > > +
> > > +static void handle_rpmsg_req_kick(struct vhost_work *work)
> > > +{
> > > +	struct vhost_virtqueue *vq = container_of(work, struct vhost_virtqueue,
> > > +						  poll.work);
> > > +	struct vhost_rpmsg *vr = container_of(vq->dev, struct vhost_rpmsg, dev);
> > > +
> > > +	while (handle_rpmsg_req_single(vr, vq))
> > > +		;
> > > +}
> > > +
> > > +/*
> > > + * initialise two virtqueues with an array of endpoints,
> > > + * request and response callbacks
> > > + */
> > > +void vhost_rpmsg_init(struct vhost_rpmsg *vr, const struct vhost_rpmsg_ept *ept,
> > > +		      unsigned int n_epts)
> > > +{
> > > +	unsigned int i;
> > > +
> > > +	for (i = 0; i < ARRAY_SIZE(vr->vq); i++)
> > > +		vr->vq_p[i] = &vr->vq[i];
> > > +
> > > +	/* vq[0]: host -> guest, vq[1]: host <- guest */
> > > +	vr->vq[VIRTIO_RPMSG_REQUEST].handle_kick = handle_rpmsg_req_kick;
> > > +	vr->vq[VIRTIO_RPMSG_RESPONSE].handle_kick = NULL;
> > 
> > The comment depicts vq[0] followed by vq[1] but the code initialise vq[1] before
> > vq[0], which is wildly confusing.  At the very least this should be: 
> 
> Nobody should care which of those is 0 and which is 1 :-) But indeed you have a point, 
> that the protocol isn't strictly request-response based, the host can also send 
> messages to the guest without preceding requests. So, TX / RX should be a better fit.
> 
> > 
> > 	vr->vq[VIRTIO_RPMSG_RESPONSE].handle_kick = NULL;
> > 	vr->vq[VIRTIO_RPMSG_REQUEST].handle_kick = handle_rpmsg_req_kick;
> > 
> > And even better:
> > 
> >         /* See configuration of *vq_cbs[] in rpmsg_probe()  */
> > 	vr->vq[VIRTIO_RPMSG_TX].handle_kick = NULL;
> > 	vr->vq[VIRTIO_RPMSG_RX].handle_kick = handle_rpmsg_req_kick;
> > 
> > > +
> > > +	vr->ept = ept;
> > > +	vr->n_epts = n_epts;
> > > +
> > > +	vhost_dev_init(&vr->dev, vr->vq_p, VIRTIO_RPMSG_NUM_OF_VQS,
> > > +		       UIO_MAXIOV, 0, 0, true, NULL);
> > > +}
> > > +EXPORT_SYMBOL_GPL(vhost_rpmsg_init);
> > > +
> > > +void vhost_rpmsg_destroy(struct vhost_rpmsg *vr)
> > > +{
> > > +	if (vhost_dev_has_owner(&vr->dev))
> > > +		vhost_poll_flush(&vr->vq[VIRTIO_RPMSG_REQUEST].poll);
> > > +
> > > +	vhost_dev_cleanup(&vr->dev);
> > > +}
> > > +EXPORT_SYMBOL_GPL(vhost_rpmsg_destroy);
> > > +
> > > +/* send namespace */
> > > +int vhost_rpmsg_ns_announce(struct vhost_rpmsg *vr, const char *name, unsigned int src)
> > > +{
> > > +	struct vhost_virtqueue *vq = &vr->vq[VIRTIO_RPMSG_RESPONSE];
> > > +	struct vhost_rpmsg_iter iter = {
> > > +		.rhdr = {
> > > +			.src = 0,
> > > +			.dst = cpu_to_vhost32(vq, RPMSG_NS_ADDR),
> > > +		},
> > > +	};
> > > +	struct rpmsg_ns_msg ns = {
> > > +		.addr = cpu_to_vhost32(vq, src),
> > > +		.flags = cpu_to_vhost32(vq, RPMSG_NS_CREATE), /* for rpmsg_ns_cb() */
> > > +	};
> > 
> > Here we have to assume the source can be found in the endpoints registered in
> > vhost_rpmsg_init().  I would put a check to make sure that is the case and
> > return an error otherwise. 
> 
> Ok, will do.
> 
> > > +	int ret = vhost_rpmsg_start_lock(vr, &iter, VIRTIO_RPMSG_RESPONSE, sizeof(ns));
> > > +
> > > +	if (ret < 0)
> > > +		return ret;
> > > +
> > > +	strlcpy(ns.name, name, sizeof(ns.name));
> > > +
> > > +	ret = vhost_rpmsg_copy(vr, &iter, &ns, sizeof(ns));
> > > +	if (ret != sizeof(ns))
> > > +		vq_err(iter.vq, "%s(): added %d instead of %zu bytes\n",
> > > +		       __func__, ret, sizeof(ns));
> > > +
> > > +	ret = vhost_rpmsg_finish_unlock(vr, &iter);
> > > +	if (ret < 0)
> > > +		vq_err(iter.vq, "%s(): namespace announcement failed: %d\n",
> > > +		       __func__, ret);
> > > +
> > > +	return ret;
> > > +}
> > > +EXPORT_SYMBOL_GPL(vhost_rpmsg_ns_announce);
> > > +
> > > +MODULE_LICENSE("GPL v2");
> > > +MODULE_AUTHOR("Intel, Inc.");
> > > +MODULE_DESCRIPTION("Vhost RPMsg API");
> > > diff --git a/drivers/vhost/vhost_rpmsg.h b/drivers/vhost/vhost_rpmsg.h
> > > new file mode 100644
> > > index 000000000000..c020ea14cd16
> > > --- /dev/null
> > > +++ b/drivers/vhost/vhost_rpmsg.h
> > > @@ -0,0 +1,74 @@
> > > +/* SPDX-License-Identifier: GPL-2.0 */
> > > +/*
> > > + * Copyright(c) 2020 Intel Corporation. All rights reserved.
> > > + *
> > > + * Author: Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>
> > > + */
> > > +
> > > +#ifndef VHOST_RPMSG_H
> > > +#define VHOST_RPMSG_H
> > > +
> > > +#include <linux/rpmsg/virtio.h>
> > > +#include <linux/uio.h>
> > > +
> > > +#include "vhost.h"
> > > +
> > > +/* RPMsg uses two VirtQueues: one for each direction */
> > > +enum {
> > > +	VIRTIO_RPMSG_RESPONSE,	/* RPMsg response (host->guest) buffers */
> > > +	VIRTIO_RPMSG_REQUEST,	/* RPMsg request (guest->host) buffers */
> > 
> > As I said above things would be much clearer if this was VIRTIO_RPMSG_TX and
> > VIRTIO_RPMSG_RX.
> 
> Ack.
> 
> > I won't be commenting on the mechanic needed to access and send information on
> > the virtqueues as it is completely foreign to me.  Other than the above I think
> > this is going somewhere. 
> 
> I'll wait for your clarifications about "coupling" and send a v8.
>

Please hold off on sending another revision.  We need to find a solution to keep
rpmsg_hdr and rpmsg_ns_msg generic (see my reply to Arnaud).

Mathieu
 
> Thanks for the comments so far
> Guennadi
> 
> > Thanks,
> > Mathieu
> > 
> > > +	/* Keep last */
> > > +	VIRTIO_RPMSG_NUM_OF_VQS,
> > > +};
> > > +
> > > +struct vhost_rpmsg_ept;
> > > +
> > > +struct vhost_rpmsg_iter {
> > > +	struct iov_iter iov_iter;
> > > +	struct rpmsg_hdr rhdr;
> > > +	struct vhost_virtqueue *vq;
> > > +	const struct vhost_rpmsg_ept *ept;
> > > +	int head;
> > > +	void *priv;
> > > +};
> > > +
> > > +struct vhost_rpmsg {
> > > +	struct vhost_dev dev;
> > > +	struct vhost_virtqueue vq[VIRTIO_RPMSG_NUM_OF_VQS];
> > > +	struct vhost_virtqueue *vq_p[VIRTIO_RPMSG_NUM_OF_VQS];
> > > +	const struct vhost_rpmsg_ept *ept;
> > > +	unsigned int n_epts;
> > > +};
> > > +
> > > +struct vhost_rpmsg_ept {
> > > +	ssize_t (*read)(struct vhost_rpmsg *, struct vhost_rpmsg_iter *);
> > > +	ssize_t (*write)(struct vhost_rpmsg *, struct vhost_rpmsg_iter *);
> > > +	int addr;
> > > +};
> > > +
> > > +static inline size_t vhost_rpmsg_iter_len(const struct vhost_rpmsg_iter *iter)
> > > +{
> > > +	return iter->rhdr.len;
> > > +}
> > > +
> > > +#define VHOST_RPMSG_ITER(_vq, _src, _dst) {			\
> > > +	.rhdr = {						\
> > > +			.src = cpu_to_vhost32(_vq, _src),	\
> > > +			.dst = cpu_to_vhost32(_vq, _dst),	\
> > > +		},						\
> > > +	}
> > > +
> > > +void vhost_rpmsg_init(struct vhost_rpmsg *vr, const struct vhost_rpmsg_ept *ept,
> > > +		      unsigned int n_epts);
> > > +void vhost_rpmsg_destroy(struct vhost_rpmsg *vr);
> > > +int vhost_rpmsg_ns_announce(struct vhost_rpmsg *vr, const char *name,
> > > +			    unsigned int src);
> > > +int vhost_rpmsg_start_lock(struct vhost_rpmsg *vr,
> > > +			   struct vhost_rpmsg_iter *iter,
> > > +			   unsigned int qid, ssize_t len);
> > > +size_t vhost_rpmsg_copy(struct vhost_rpmsg *vr, struct vhost_rpmsg_iter *iter,
> > > +			void *data, size_t size);
> > > +int vhost_rpmsg_finish_unlock(struct vhost_rpmsg *vr,
> > > +			      struct vhost_rpmsg_iter *iter);
> > > +
> > > +#endif
> > > -- 
> > > 2.28.0
> > >