[PATCH v2 5/5] vhost: add an RPMsg API

Guennadi Liakhovetski
2020-05-25T14:44:58Z

Linux supports running the RPMsg protocol over the VirtIO transport
protocol, but currently there is only support for VirtIO clients and
no support for a VirtIO server. This patch adds a vhost-based RPMsg
server implementation.

Signed-off-by: Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>
---
drivers/vhost/Kconfig | 7 +
drivers/vhost/Makefile | 3 +
drivers/vhost/rpmsg.c | 372 ++++++++++++++++++++++++++++++++++++++++++++
drivers/vhost/vhost_rpmsg.h | 74 +++++++++
4 files changed, 456 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 2c75d16..c2113db 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
+ depends on VHOST
+ ---help---
+ Vhost RPMsg API allows vhost drivers to communicate with VirtIO
+ drivers, using the RPMsg over VirtIO protocol.
+
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 f3e1897..9cf459d 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 00000000..609b9cf
--- /dev/null
+++ b/drivers/vhost/rpmsg.c
@@ -0,0 +1,372 @@
+/* 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
+ */
+
+#include <linux/compat.h>
+#include <linux/file.h>
+#include <linux/miscdevice.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/vhost.h>
+#include <linux/virtio_rpmsg.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
+ */
+static int vhost_rpmsg_get_single(struct vhost_virtqueue *vq)
+{
+ 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] && (out || in != 1)) {
+ vq_err(vq,
+ "%s(): invalid %d input and %d output in response queue\n",
+ __func__, in, out);
+ goto return_buf;
+ }
+
+ if (vq == &vr->vq[VIRTIO_RPMSG_REQUEST] && (in || out != 1)) {
+ vq_err(vq,
+ "%s(): invalid %d input and %d output in request queue\n",
+ __func__, in, out);
+ goto return_buf;
+ }
+
+ return head;
+
+return_buf:
+ /*
+ * FIXME: might need to return the buffer using vhost_add_used()
+ * or vhost_discard_vq_desc(). vhost_discard_vq_desc() is
+ * described as "being useful for error handling," but it makes
+ * the thus discarded buffers "unseen," so next time we look we
+ * retrieve them again?
+ */
+ 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;
+ 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_single(vq);
+ if (iter->head == vq->num)
+ iter->head = -EAGAIN;
+
+ if (iter->head < 0)
+ goto unlock;
+
+ tmp = vq->iov[0].iov_len;
+ if (tmp < sizeof(iter->rhdr)) {
+ vq_err(vq, "%s(): size %zu too small\n", __func__, tmp);
+ iter->head = -ENOBUFS;
+ goto return_buf;
+ }
+
+ switch (qid) {
+ case VIRTIO_RPMSG_REQUEST:
+ if (len < 0) {
+ len = tmp - sizeof(iter->rhdr);
+ } else if (tmp < sizeof(iter->rhdr) + len) {
+ iter->head = -ENOBUFS;
+ goto return_buf;
+ }
+
+ /* len is now the size of the payload */
+ iov_iter_init(&iter->iov_iter, WRITE,
+ vq->iov, 1, sizeof(iter->rhdr) + len);
+
+ /* 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));
+ iter->head = -EIO;
+ goto return_buf;
+ }
+
+ iter->ept = vhost_rpmsg_ept_find(vr, iter->rhdr.dst);
+ if (!iter->ept) {
+ vq_err(vq, "%s(): no endpoint with address %d\n",
+ __func__, iter->rhdr.dst);
+ iter->head = -ENOENT;
+ goto return_buf;
+ }
+
+ /* Let the endpoint read the payload */
+ if (iter->ept->read) {
+ ssize_t ret = iter->ept->read(vr, iter);
+ if (ret < 0) {
+ iter->head = ret;
+ goto return_buf;
+ }
+
+ iter->rhdr.len = ret;
+ } else {
+ iter->rhdr.len = 0;
+ }
+
+ /* Prepare for the response phase */
+ iter->rhdr.dst = iter->rhdr.src;
+ iter->rhdr.src = iter->ept->addr;
+
+ break;
+ case VIRTIO_RPMSG_RESPONSE:
+ if (!iter->ept && iter->rhdr.dst != 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, iter->rhdr.src);
+ if (!iter->ept) {
+ iter->head = -ENOENT;
+ goto return_buf;
+ }
+ }
+
+ if (len < 0) {
+ len = tmp - sizeof(iter->rhdr);
+ } else if (tmp < sizeof(iter->rhdr) + len) {
+ iter->head = -ENOBUFS;
+ goto return_buf;
+ } else {
+ iter->rhdr.len = len;
+ }
+
+ /* len is now the size of the payload */
+ iov_iter_init(&iter->iov_iter, READ,
+ vq->iov, 1, sizeof(iter->rhdr) + len);
+
+ /* Write the RPMSG header with endpoint addresses */
+ tmp = copy_to_iter(&iter->rhdr, sizeof(iter->rhdr),
+ &iter->iov_iter);
+ if (tmp != sizeof(iter->rhdr)) {
+ iter->head = -EIO;
+ goto return_buf;
+ }
+
+ /* Let the endpoint write the payload */
+ if (iter->ept && iter->ept->write) {
+ ssize_t ret = iter->ept->write(vr, iter);
+ if (ret < 0) {
+ iter->head = ret;
+ goto return_buf;
+ }
+ }
+
+ break;
+ }
+
+ return 0;
+
+return_buf:
+ /*
+ * FIXME: vhost_discard_vq_desc() or vhost_add_used(), see comment in
+ * vhost_rpmsg_get_single()
+ */
+unlock:
+ vhost_enable_notify(&vr->dev, vq);
+ mutex_unlock(&vq->mutex);
+
+ return iter->head;
+}
+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,
+ 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;
+ }
+
+ 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->ept = ept;
+ vr->n_epts = n_epts;
+
+ vhost_dev_init(&vr->dev, vr->vq_p, VIRTIO_RPMSG_NUM_OF_VQS,
+ UIO_MAXIOV, 0, 0, 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_rpmsg_iter iter = {
+ .rhdr = {
+ .src = 0,
+ .dst = RPMSG_NS_ADDR,
+ .flags = RPMSG_NS_CREATE, /* rpmsg_recv_single() */
+ },
+ };
+ struct rpmsg_ns_msg ns = {
+ .addr = src,
+ .flags = RPMSG_NS_CREATE, /* for rpmsg_ns_cb() */
+ };
+ 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 00000000..5248ac9
--- /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/uio.h>
+#include <linux/virtio_rpmsg.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 */
+ /* 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(_src, _dst) { \
+ .rhdr = { \
+ .src = _src, \
+ .dst = _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
--
1.9.3