[PATCH v2 0/5] Add a vhost RPMsg API

[PATCH v2 0/5] Add a vhost RPMsg API

[Guennadi Liakhovetski]

v2:
- remove "default n" from Kconfig
- drop patch #6 - it depends on a different patch, that is currently 
  an RFC
- update patch #5 with a correct vhost_dev_init() prototype

Linux supports RPMsg over VirtIO for "remote processor" /AMP use
cases. It can however also be used for virtualisation scenarios,
e.g. when using KVM to run Linux on both the host and the guests.
This patch set adds a wrapper API to facilitate writing vhost
drivers for such RPMsg-based solutions. The first use case is an
audio DSP virtualisation project, currently under development, ready
for review and submission, available at
https://github.com/thesofproject/linux/pull/1501/commits
A further patch for the ADSP vhost RPMsg driver will be sent
separately for review only since it cannot be merged without audio
patches being upstreamed first.

Thanks
Guennadi

Guennadi Liakhovetski (5):
  vhost: convert VHOST_VSOCK_SET_RUNNING to a generic ioctl
  vhost: (cosmetic) remove a superfluous variable initialisation
  rpmsg: move common structures and defines to headers
  rpmsg: update documentation
  vhost: add an rpmsg API

 Documentation/rpmsg.txt          |   2 +-
 drivers/rpmsg/virtio_rpmsg_bus.c |  78 +-------
 drivers/vhost/Kconfig            |   7 +
 drivers/vhost/Makefile           |   3 +
 drivers/vhost/rpmsg.c            | 372 +++++++++++++++++++++++++++++++++++++++
 drivers/vhost/vhost.c            |   2 +-
 drivers/vhost/vhost_rpmsg.h      |  74 ++++++++
 include/linux/virtio_rpmsg.h     |  81 +++++++++
 include/uapi/linux/rpmsg.h       |   3 +
 include/uapi/linux/vhost.h       |   4 +-
 10 files changed, 547 insertions(+), 79 deletions(-)
 create mode 100644 drivers/vhost/rpmsg.c
 create mode 100644 drivers/vhost/vhost_rpmsg.h
 create mode 100644 include/linux/virtio_rpmsg.h

-- 
1.9.3

[PATCH v2 1/5] vhost: convert VHOST_VSOCK_SET_RUNNING to a generic ioctl

[Guennadi Liakhovetski]

VHOST_VSOCK_SET_RUNNING is used by the vhost vsock driver to perform
crucial VirtQueue initialisation, like assigning .private fields and
calling vhost_vq_init_access(), and clean up. However, this ioctl is
actually extremely useful for any vhost driver, that doesn't have a
side channel to inform it of a status change, e.g. upon a guest
reboot. This patch makes that ioctl generic, while preserving its
numeric value and also keeping the original alias.

Signed-off-by: Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>
---
 include/uapi/linux/vhost.h | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h
index 9fe72e4..b54af9d 100644
--- a/include/uapi/linux/vhost.h
+++ b/include/uapi/linux/vhost.h
@@ -93,6 +93,8 @@
 #define VHOST_SET_BACKEND_FEATURES _IOW(VHOST_VIRTIO, 0x25, __u64)
 #define VHOST_GET_BACKEND_FEATURES _IOR(VHOST_VIRTIO, 0x26, __u64)
 
+#define VHOST_SET_RUNNING _IOW(VHOST_VIRTIO, 0x61, int)
+
 /* VHOST_NET specific defines */
 
 /* Attach virtio net ring to a raw socket, or tap device.
@@ -114,7 +116,7 @@
 /* VHOST_VSOCK specific defines */
 
 #define VHOST_VSOCK_SET_GUEST_CID	_IOW(VHOST_VIRTIO, 0x60, __u64)
-#define VHOST_VSOCK_SET_RUNNING		_IOW(VHOST_VIRTIO, 0x61, int)
+#define VHOST_VSOCK_SET_RUNNING		VHOST_SET_RUNNING
 
 /* VHOST_VDPA specific defines */
 
-- 
1.9.3

[PATCH v2 2/5] vhost: (cosmetic) remove a superfluous variable initialisation

[Guennadi Liakhovetski]

Even the compiler is able to figure out that in this case the
initialisation is superfluous.

Signed-off-by: Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>
---
 drivers/vhost/vhost.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 2f4383bb..2b9ad8a 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -895,7 +895,7 @@ static inline void __user *__vhost_get_user(struct vhost_virtqueue *vq,
 
 #define vhost_put_user(vq, x, ptr)		\
 ({ \
-	int ret = -EFAULT; \
+	int ret; \
 	if (!vq->iotlb) { \
 		ret = __put_user(x, ptr); \
 	} else { \
-- 
1.9.3

[PATCH v2 3/5] rpmsg: move common structures and defines to headers

[Guennadi Liakhovetski]

virtio_rpmsg_bus.c keeps RPMsg protocol structure declarations and
common defines like the ones, needed for name-space announcements,
internal. Move them to common headers instead.

Signed-off-by: Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>
---
 drivers/rpmsg/virtio_rpmsg_bus.c | 78 +-------------------------------------
 include/linux/virtio_rpmsg.h     | 81 ++++++++++++++++++++++++++++++++++++++++
 include/uapi/linux/rpmsg.h       |  3 ++
 3 files changed, 86 insertions(+), 76 deletions(-)
 create mode 100644 include/linux/virtio_rpmsg.h

diff --git a/drivers/rpmsg/virtio_rpmsg_bus.c b/drivers/rpmsg/virtio_rpmsg_bus.c
index 07d4f33..f3bd050 100644
--- a/drivers/rpmsg/virtio_rpmsg_bus.c
+++ b/drivers/rpmsg/virtio_rpmsg_bus.c
@@ -25,7 +25,9 @@
 #include <linux/virtio.h>
 #include <linux/virtio_ids.h>
 #include <linux/virtio_config.h>
+#include <linux/virtio_rpmsg.h>
 #include <linux/wait.h>
+#include <uapi/linux/rpmsg.h>
 
 #include "rpmsg_internal.h"
 
@@ -69,58 +71,6 @@ struct virtproc_info {
 	struct rpmsg_endpoint *ns_ept;
 };
 
-/* The feature bitmap for virtio rpmsg */
-#define VIRTIO_RPMSG_F_NS	0 /* RP supports name service notifications */
-
-/**
- * struct rpmsg_hdr - common header for all rpmsg messages
- * @src: source address
- * @dst: destination address
- * @reserved: reserved for future use
- * @len: length of payload (in bytes)
- * @flags: message flags
- * @data: @len bytes of message payload data
- *
- * Every message sent(/received) on the rpmsg bus begins with this header.
- */
-struct rpmsg_hdr {
-	u32 src;
-	u32 dst;
-	u32 reserved;
-	u16 len;
-	u16 flags;
-	u8 data[];
-} __packed;
-
-/**
- * struct rpmsg_ns_msg - dynamic name service announcement message
- * @name: name of remote service that is published
- * @addr: address of remote service that is published
- * @flags: indicates whether service is created or destroyed
- *
- * This message is sent across to publish a new service, or announce
- * about its removal. When we receive these messages, an appropriate
- * rpmsg channel (i.e device) is created/destroyed. In turn, the ->probe()
- * or ->remove() handler of the appropriate rpmsg driver will be invoked
- * (if/as-soon-as one is registered).
- */
-struct rpmsg_ns_msg {
-	char name[RPMSG_NAME_SIZE];
-	u32 addr;
-	u32 flags;
-} __packed;
-
-/**
- * enum rpmsg_ns_flags - dynamic name service announcement flags
- *
- * @RPMSG_NS_CREATE: a new remote service was just created
- * @RPMSG_NS_DESTROY: a known remote service was just destroyed
- */
-enum rpmsg_ns_flags {
-	RPMSG_NS_CREATE		= 0,
-	RPMSG_NS_DESTROY	= 1,
-};
-
 /**
  * @vrp: the remote processor this channel belongs to
  */
@@ -134,36 +84,12 @@ struct virtio_rpmsg_channel {
 	container_of(_rpdev, struct virtio_rpmsg_channel, rpdev)
 
 /*
- * We're allocating buffers of 512 bytes each for communications. The
- * number of buffers will be computed from the number of buffers supported
- * by the vring, upto a maximum of 512 buffers (256 in each direction).
- *
- * Each buffer will have 16 bytes for the msg header and 496 bytes for
- * the payload.
- *
- * This will utilize a maximum total space of 256KB for the buffers.
- *
- * We might also want to add support for user-provided buffers in time.
- * This will allow bigger buffer size flexibility, and can also be used
- * to achieve zero-copy messaging.
- *
- * Note that these numbers are purely a decision of this driver - we
- * can change this without changing anything in the firmware of the remote
- * processor.
- */
-#define MAX_RPMSG_NUM_BUFS	(512)
-#define MAX_RPMSG_BUF_SIZE	(512)
-
-/*
  * Local addresses are dynamically allocated on-demand.
  * We do not dynamically assign addresses from the low 1024 range,
  * in order to reserve that address range for predefined services.
  */
 #define RPMSG_RESERVED_ADDRESSES	(1024)
 
-/* Address 53 is reserved for advertising remote services */
-#define RPMSG_NS_ADDR			(53)
-
 static void virtio_rpmsg_destroy_ept(struct rpmsg_endpoint *ept);
 static int virtio_rpmsg_send(struct rpmsg_endpoint *ept, void *data, int len);
 static int virtio_rpmsg_sendto(struct rpmsg_endpoint *ept, void *data, int len,
diff --git a/include/linux/virtio_rpmsg.h b/include/linux/virtio_rpmsg.h
new file mode 100644
index 00000000..bf2fd69
--- /dev/null
+++ b/include/linux/virtio_rpmsg.h
@@ -0,0 +1,81 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#ifndef _LINUX_VIRTIO_RPMSG_H
+#define _LINUX_VIRTIO_RPMSG_H
+
+#include <linux/mod_devicetable.h>
+
+/* Address 53 is reserved for advertising remote services */
+#define RPMSG_NS_ADDR			(53)
+
+/*
+ * We're allocating buffers of 512 bytes each for communications. The
+ * number of buffers will be computed from the number of buffers supported
+ * by the vring, upto a maximum of 512 buffers (256 in each direction).
+ *
+ * Each buffer will have 16 bytes for the msg header and 496 bytes for
+ * the payload.
+ *
+ * This will utilize a maximum total space of 256KB for the buffers.
+ *
+ * We might also want to add support for user-provided buffers in time.
+ * This will allow bigger buffer size flexibility, and can also be used
+ * to achieve zero-copy messaging.
+ *
+ * Note that these numbers are purely a decision of this driver - we
+ * can change this without changing anything in the firmware of the remote
+ * processor.
+ */
+#define MAX_RPMSG_NUM_BUFS	512
+#define MAX_RPMSG_BUF_SIZE	512
+
+/**
+ * struct rpmsg_hdr - common header for all rpmsg messages
+ * @src: source address
+ * @dst: destination address
+ * @reserved: reserved for future use
+ * @len: length of payload (in bytes)
+ * @flags: message flags
+ * @data: @len bytes of message payload data
+ *
+ * Every message sent(/received) on the rpmsg bus begins with this header.
+ */
+struct rpmsg_hdr {
+	u32 src;
+	u32 dst;
+	u32 reserved;
+	u16 len;
+	u16 flags;
+	u8 data[];
+} __packed;
+
+/**
+ * struct rpmsg_ns_msg - dynamic name service announcement message
+ * @name: name of remote service that is published
+ * @addr: address of remote service that is published
+ * @flags: indicates whether service is created or destroyed
+ *
+ * This message is sent across to publish a new service, or announce
+ * about its removal. When we receive these messages, an appropriate
+ * rpmsg channel (i.e device) is created/destroyed. In turn, the ->probe()
+ * or ->remove() handler of the appropriate rpmsg driver will be invoked
+ * (if/as-soon-as one is registered).
+ */
+struct rpmsg_ns_msg {
+	char name[RPMSG_NAME_SIZE];
+	u32 addr;
+	u32 flags;
+} __packed;
+
+/**
+ * enum rpmsg_ns_flags - dynamic name service announcement flags
+ *
+ * @RPMSG_NS_CREATE: a new remote service was just created
+ * @RPMSG_NS_DESTROY: a known remote service was just destroyed
+ */
+enum rpmsg_ns_flags {
+	RPMSG_NS_CREATE		= 0,
+	RPMSG_NS_DESTROY	= 1,
+};
+
+#endif
diff --git a/include/uapi/linux/rpmsg.h b/include/uapi/linux/rpmsg.h
index e14c6da..d669c04 100644
--- a/include/uapi/linux/rpmsg.h
+++ b/include/uapi/linux/rpmsg.h
@@ -24,4 +24,7 @@ struct rpmsg_endpoint_info {
 #define RPMSG_CREATE_EPT_IOCTL	_IOW(0xb5, 0x1, struct rpmsg_endpoint_info)
 #define RPMSG_DESTROY_EPT_IOCTL	_IO(0xb5, 0x2)
 
+/* The feature bitmap for virtio rpmsg */
+#define VIRTIO_RPMSG_F_NS	0 /* RP supports name service notifications */
+
 #endif
-- 
1.9.3

[PATCH v2 4/5] rpmsg: update documentation

[Guennadi Liakhovetski]

rpmsg_create_ept() takes struct rpmsg_channel_info chinfo as its last
argument, not a u32 value.

Signed-off-by: Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>
---
 Documentation/rpmsg.txt | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Documentation/rpmsg.txt b/Documentation/rpmsg.txt
index 24b7a9e..4f9bc4f 100644
--- a/Documentation/rpmsg.txt
+++ b/Documentation/rpmsg.txt
@@ -194,7 +194,7 @@ Returns 0 on success and an appropriate error value on failure.
 
   struct rpmsg_endpoint *rpmsg_create_ept(struct rpmsg_channel *rpdev,
 		void (*cb)(struct rpmsg_channel *, void *, int, void *, u32),
-		void *priv, u32 addr);
+		void *priv, struct rpmsg_channel_info chinfo);
 
 every rpmsg address in the system is bound to an rx callback (so when
 inbound messages arrive, they are dispatched by the rpmsg bus using the
-- 
1.9.3

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

[Guennadi Liakhovetski]

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

Re: [PATCH v2 3/5] rpmsg: move common structures and defines to headers

[Mathieu Poirier]

Hi Guennadi,

On Mon, May 25, 2020 at 04:44:56PM +0200, Guennadi Liakhovetski wrote:
> virtio_rpmsg_bus.c keeps RPMsg protocol structure declarations and
> common defines like the ones, needed for name-space announcements,
> internal. Move them to common headers instead.
> 
> Signed-off-by: Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>
> ---
>  drivers/rpmsg/virtio_rpmsg_bus.c | 78 +-------------------------------------
>  include/linux/virtio_rpmsg.h     | 81 ++++++++++++++++++++++++++++++++++++++++
>  include/uapi/linux/rpmsg.h       |  3 ++
>  3 files changed, 86 insertions(+), 76 deletions(-)
>  create mode 100644 include/linux/virtio_rpmsg.h
> 
> diff --git a/drivers/rpmsg/virtio_rpmsg_bus.c b/drivers/rpmsg/virtio_rpmsg_bus.c
> index 07d4f33..f3bd050 100644
> --- a/drivers/rpmsg/virtio_rpmsg_bus.c
> +++ b/drivers/rpmsg/virtio_rpmsg_bus.c
> @@ -25,7 +25,9 @@
>  #include <linux/virtio.h>
>  #include <linux/virtio_ids.h>
>  #include <linux/virtio_config.h>
> +#include <linux/virtio_rpmsg.h>
>  #include <linux/wait.h>
> +#include <uapi/linux/rpmsg.h>
>  
>  #include "rpmsg_internal.h"
>  
> @@ -69,58 +71,6 @@ struct virtproc_info {
>  	struct rpmsg_endpoint *ns_ept;
>  };
>  
> -/* The feature bitmap for virtio rpmsg */
> -#define VIRTIO_RPMSG_F_NS	0 /* RP supports name service notifications */
> -
> -/**
> - * struct rpmsg_hdr - common header for all rpmsg messages
> - * @src: source address
> - * @dst: destination address
> - * @reserved: reserved for future use
> - * @len: length of payload (in bytes)
> - * @flags: message flags
> - * @data: @len bytes of message payload data
> - *
> - * Every message sent(/received) on the rpmsg bus begins with this header.
> - */
> -struct rpmsg_hdr {
> -	u32 src;
> -	u32 dst;
> -	u32 reserved;
> -	u16 len;
> -	u16 flags;
> -	u8 data[];
> -} __packed;
> -
> -/**
> - * struct rpmsg_ns_msg - dynamic name service announcement message
> - * @name: name of remote service that is published
> - * @addr: address of remote service that is published
> - * @flags: indicates whether service is created or destroyed
> - *
> - * This message is sent across to publish a new service, or announce
> - * about its removal. When we receive these messages, an appropriate
> - * rpmsg channel (i.e device) is created/destroyed. In turn, the ->probe()
> - * or ->remove() handler of the appropriate rpmsg driver will be invoked
> - * (if/as-soon-as one is registered).
> - */
> -struct rpmsg_ns_msg {
> -	char name[RPMSG_NAME_SIZE];
> -	u32 addr;
> -	u32 flags;
> -} __packed;
> -
> -/**
> - * enum rpmsg_ns_flags - dynamic name service announcement flags
> - *
> - * @RPMSG_NS_CREATE: a new remote service was just created
> - * @RPMSG_NS_DESTROY: a known remote service was just destroyed
> - */
> -enum rpmsg_ns_flags {
> -	RPMSG_NS_CREATE		= 0,
> -	RPMSG_NS_DESTROY	= 1,
> -};
> -
>  /**
>   * @vrp: the remote processor this channel belongs to
>   */
> @@ -134,36 +84,12 @@ struct virtio_rpmsg_channel {
>  	container_of(_rpdev, struct virtio_rpmsg_channel, rpdev)
>  
>  /*
> - * We're allocating buffers of 512 bytes each for communications. The
> - * number of buffers will be computed from the number of buffers supported
> - * by the vring, upto a maximum of 512 buffers (256 in each direction).
> - *
> - * Each buffer will have 16 bytes for the msg header and 496 bytes for
> - * the payload.
> - *
> - * This will utilize a maximum total space of 256KB for the buffers.
> - *
> - * We might also want to add support for user-provided buffers in time.
> - * This will allow bigger buffer size flexibility, and can also be used
> - * to achieve zero-copy messaging.
> - *
> - * Note that these numbers are purely a decision of this driver - we
> - * can change this without changing anything in the firmware of the remote
> - * processor.
> - */
> -#define MAX_RPMSG_NUM_BUFS	(512)
> -#define MAX_RPMSG_BUF_SIZE	(512)
> -
> -/*
>   * Local addresses are dynamically allocated on-demand.
>   * We do not dynamically assign addresses from the low 1024 range,
>   * in order to reserve that address range for predefined services.
>   */
>  #define RPMSG_RESERVED_ADDRESSES	(1024)
>  
> -/* Address 53 is reserved for advertising remote services */
> -#define RPMSG_NS_ADDR			(53)
> -
>  static void virtio_rpmsg_destroy_ept(struct rpmsg_endpoint *ept);
>  static int virtio_rpmsg_send(struct rpmsg_endpoint *ept, void *data, int len);
>  static int virtio_rpmsg_sendto(struct rpmsg_endpoint *ept, void *data, int len,
> diff --git a/include/linux/virtio_rpmsg.h b/include/linux/virtio_rpmsg.h
> new file mode 100644
> index 00000000..bf2fd69
> --- /dev/null
> +++ b/include/linux/virtio_rpmsg.h
> @@ -0,0 +1,81 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#ifndef _LINUX_VIRTIO_RPMSG_H
> +#define _LINUX_VIRTIO_RPMSG_H
> +
> +#include <linux/mod_devicetable.h>
> +
> +/* Address 53 is reserved for advertising remote services */
> +#define RPMSG_NS_ADDR			(53)
> +
> +/*
> + * We're allocating buffers of 512 bytes each for communications. The
> + * number of buffers will be computed from the number of buffers supported
> + * by the vring, upto a maximum of 512 buffers (256 in each direction).
> + *
> + * Each buffer will have 16 bytes for the msg header and 496 bytes for
> + * the payload.
> + *
> + * This will utilize a maximum total space of 256KB for the buffers.
> + *
> + * We might also want to add support for user-provided buffers in time.
> + * This will allow bigger buffer size flexibility, and can also be used
> + * to achieve zero-copy messaging.
> + *
> + * Note that these numbers are purely a decision of this driver - we
> + * can change this without changing anything in the firmware of the remote
> + * processor.
> + */
> +#define MAX_RPMSG_NUM_BUFS	512
> +#define MAX_RPMSG_BUF_SIZE	512
> +
> +/**
> + * struct rpmsg_hdr - common header for all rpmsg messages
> + * @src: source address
> + * @dst: destination address
> + * @reserved: reserved for future use
> + * @len: length of payload (in bytes)
> + * @flags: message flags
> + * @data: @len bytes of message payload data
> + *
> + * Every message sent(/received) on the rpmsg bus begins with this header.
> + */
> +struct rpmsg_hdr {
> +	u32 src;
> +	u32 dst;
> +	u32 reserved;
> +	u16 len;
> +	u16 flags;
> +	u8 data[];
> +} __packed;
> +
> +/**
> + * struct rpmsg_ns_msg - dynamic name service announcement message
> + * @name: name of remote service that is published
> + * @addr: address of remote service that is published
> + * @flags: indicates whether service is created or destroyed
> + *
> + * This message is sent across to publish a new service, or announce
> + * about its removal. When we receive these messages, an appropriate
> + * rpmsg channel (i.e device) is created/destroyed. In turn, the ->probe()
> + * or ->remove() handler of the appropriate rpmsg driver will be invoked
> + * (if/as-soon-as one is registered).
> + */
> +struct rpmsg_ns_msg {
> +	char name[RPMSG_NAME_SIZE];
> +	u32 addr;
> +	u32 flags;
> +} __packed;
> +
> +/**
> + * enum rpmsg_ns_flags - dynamic name service announcement flags
> + *
> + * @RPMSG_NS_CREATE: a new remote service was just created
> + * @RPMSG_NS_DESTROY: a known remote service was just destroyed
> + */
> +enum rpmsg_ns_flags {
> +	RPMSG_NS_CREATE		= 0,
> +	RPMSG_NS_DESTROY	= 1,
> +};
> +

I have started reviewing this set and comments will (likely) come over a few
days.

For this file, I would have appreciated seeing the structure and defines laid
out in the same order in this file as they were in virtio_rpmsg_bus.c.  That way
I don't have to check every item to make sure nothing has been missed.  Not a
big problem but something to consider for the next revivions.  

The good thing is that it did not break my complation so with above:

Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org>

> +#endif
> diff --git a/include/uapi/linux/rpmsg.h b/include/uapi/linux/rpmsg.h
> index e14c6da..d669c04 100644
> --- a/include/uapi/linux/rpmsg.h
> +++ b/include/uapi/linux/rpmsg.h
> @@ -24,4 +24,7 @@ struct rpmsg_endpoint_info {
>  #define RPMSG_CREATE_EPT_IOCTL	_IOW(0xb5, 0x1, struct rpmsg_endpoint_info)
>  #define RPMSG_DESTROY_EPT_IOCTL	_IO(0xb5, 0x2)
>  
> +/* The feature bitmap for virtio rpmsg */
> +#define VIRTIO_RPMSG_F_NS	0 /* RP supports name service notifications */
> +
>  #endif
> -- 
> 1.9.3
> 

Re: [PATCH v2 4/5] rpmsg: update documentation

[Mathieu Poirier]

On Mon, May 25, 2020 at 04:44:57PM +0200, Guennadi Liakhovetski wrote:
> rpmsg_create_ept() takes struct rpmsg_channel_info chinfo as its last
> argument, not a u32 value.
> 
> Signed-off-by: Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>
> ---
>  Documentation/rpmsg.txt | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/Documentation/rpmsg.txt b/Documentation/rpmsg.txt
> index 24b7a9e..4f9bc4f 100644
> --- a/Documentation/rpmsg.txt
> +++ b/Documentation/rpmsg.txt
> @@ -194,7 +194,7 @@ Returns 0 on success and an appropriate error value on failure.
>  
>    struct rpmsg_endpoint *rpmsg_create_ept(struct rpmsg_channel *rpdev,
>  		void (*cb)(struct rpmsg_channel *, void *, int, void *, u32),
> -		void *priv, u32 addr);
> +		void *priv, struct rpmsg_channel_info chinfo);

The second argument, i.e *cb is also wrong.  The first argument to the function
pointer is a struct rpmsg_device rather than a rpmsg_channel.  Please fix that
while at it by simply using "rpmsg_rx_cb_t cb", the same way it is in
linux/rpmsg.h.

Thanks,
Mathieu

>  
>  every rpmsg address in the system is bound to an rx callback (so when
>  inbound messages arrive, they are dispatched by the rpmsg bus using the
> -- 
> 1.9.3
> 

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

[Mathieu Poirier]

On Mon, May 25, 2020 at 04:44:58PM +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 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

This patch triggers several checkpatch warnings, and from what I see none of
them helping with code readability.  Please consider addressing.

More comments to follow tomorrow.

> 
> 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
> 

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

[Mathieu Poirier]

Hi Guennadi,

On Mon, May 25, 2020 at 04:44:58PM +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 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() */
> +	};

I think it would be worth mentioning that someone on the guest side needs to
call register_virtio_device() with a vdev->id->device == VIRTIO_ID_RPMSG,
something that will match that device to the virtio_ipc_driver.  Otherwise the
connection between them is very difficult to establish.

Aside from the checkpatch warning I already pointed out, I don't have much else.

Thanks,
Mathieu

> +	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
> 

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

[Guennadi Liakhovetski]

Hi Mathieu,

On Tue, May 26, 2020 at 02:50:39PM -0600, Mathieu Poirier wrote:
> Hi Guennadi,
> 
> On Mon, May 25, 2020 at 04:44:58PM +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 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

[snip]

> > +/* 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() */
> > +	};
> 
> I think it would be worth mentioning that someone on the guest side needs to
> call register_virtio_device() with a vdev->id->device == VIRTIO_ID_RPMSG,
> something that will match that device to the virtio_ipc_driver.  Otherwise the
> connection between them is very difficult to establish.

In fact you don't want to use just one ID, as you add more drivers, using RPMsg 
over VirtIO, you'll add more IDs to the ID table in virtio_rpmsg_bus.c. I am 
adding a comment at the top of this file to explain that.

Thanks
Guennadi

> Aside from the checkpatch warning I already pointed out, I don't have much else.
> 
> Thanks,
> Mathieu
> 
> > +	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
> >