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Message-ID: <20251114184640.3020427-3-tanmay.shah@amd.com>
Date: Fri, 14 Nov 2025 10:46:40 -0800
From: Tanmay Shah <tanmay.shah@....com>
To: <andersson@...nel.org>, <mathieu.poirier@...aro.org>, <mst@...hat.com>,
<jasowang@...hat.com>, <xuanzhuo@...ux.alibaba.com>, <eperezma@...hat.com>
CC: <linux-kernel@...r.kernel.org>, <linux-remoteproc@...r.kernel.org>,
<virtualization@...ts.linux.dev>, <xiaoxiang@...omi.com>, Xiang Xiao
<xiaoxiang781216@...il.com>, Tanmay Shah <tanmay.shah@....com>
Subject: [RFC PATCH 2/2] rpmsg: virtio_rpmsg_bus: get buffer size from config space
From: Xiang Xiao <xiaoxiang781216@...il.com>
512 bytes isn't always suitable for all case, let firmware
maker decide the best value from resource table.
enable by VIRTIO_RPMSG_F_BUFSZ feature bit.
Signed-off-by: Xiang Xiao <xiaoxiang@...omi.com>
Signed-off-by: Tanmay Shah <tanmay.shah@....com>
---
drivers/rpmsg/virtio_rpmsg_bus.c | 68 +++++++++++++++++++++++---------
include/linux/virtio_rpmsg.h | 24 +++++++++++
2 files changed, 74 insertions(+), 18 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 cc26dfcc3e29..03dd5535880a 100644
--- a/drivers/rpmsg/virtio_rpmsg_bus.c
+++ b/drivers/rpmsg/virtio_rpmsg_bus.c
@@ -25,6 +25,7 @@
#include <linux/sched.h>
#include <linux/virtio.h>
#include <linux/virtio_ids.h>
+#include <linux/virtio_rpmsg.h>
#include <linux/virtio_config.h>
#include <linux/wait.h>
@@ -39,7 +40,8 @@
* @sbufs: kernel address of tx buffers
* @num_rbufs: total number of buffers for rx
* @num_sbufs: total number of buffers for tx
- * @buf_size: size of one rx or tx buffer
+ * @rbuf_size: size of one rx buffer
+ * @sbuf_size: size of one tx buffer
* @last_sbuf: index of last tx buffer used
* @bufs_dma: dma base addr of the buffers
* @tx_lock: protects svq, sbufs and sleepers, to allow concurrent senders.
@@ -60,7 +62,8 @@ struct virtproc_info {
void *rbufs, *sbufs;
unsigned int num_rbufs;
unsigned int num_sbufs;
- unsigned int buf_size;
+ unsigned int rbuf_size;
+ unsigned int sbuf_size;
int last_sbuf;
dma_addr_t bufs_dma;
struct mutex tx_lock;
@@ -70,9 +73,6 @@ struct virtproc_info {
atomic_t sleepers;
};
-/* 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
@@ -130,7 +130,7 @@ struct virtio_rpmsg_channel {
* processor.
*/
#define MAX_RPMSG_NUM_BUFS (256)
-#define MAX_RPMSG_BUF_SIZE (512)
+#define DEFAULT_RPMSG_BUF_SIZE (512)
/*
* Local addresses are dynamically allocated on-demand.
@@ -443,7 +443,7 @@ static void *get_a_tx_buf(struct virtproc_info *vrp)
/* either pick the next unused tx buffer */
if (vrp->last_sbuf < vrp->num_sbufs)
- ret = vrp->sbufs + vrp->buf_size * vrp->last_sbuf++;
+ ret = vrp->sbufs + vrp->sbuf_size * vrp->last_sbuf++;
/* or recycle a used one */
else
ret = virtqueue_get_buf(vrp->svq, &len);
@@ -569,7 +569,7 @@ static int rpmsg_send_offchannel_raw(struct rpmsg_device *rpdev,
* messaging), or to improve the buffer allocator, to support
* variable-length buffer sizes.
*/
- if (len > vrp->buf_size - sizeof(struct rpmsg_hdr)) {
+ if (len > vrp->sbuf_size - sizeof(struct rpmsg_hdr)) {
dev_err(dev, "message is too big (%d)\n", len);
return -EMSGSIZE;
}
@@ -680,7 +680,7 @@ static ssize_t virtio_rpmsg_get_mtu(struct rpmsg_endpoint *ept)
struct rpmsg_device *rpdev = ept->rpdev;
struct virtio_rpmsg_channel *vch = to_virtio_rpmsg_channel(rpdev);
- return vch->vrp->buf_size - sizeof(struct rpmsg_hdr);
+ return vch->vrp->sbuf_size - sizeof(struct rpmsg_hdr);
}
static int rpmsg_recv_single(struct virtproc_info *vrp, struct device *dev,
@@ -706,7 +706,7 @@ static int rpmsg_recv_single(struct virtproc_info *vrp, struct device *dev,
* We currently use fixed-sized buffers, so trivially sanitize
* the reported payload length.
*/
- if (len > vrp->buf_size ||
+ if (len > vrp->rbuf_size ||
msg_len > (len - sizeof(struct rpmsg_hdr))) {
dev_warn(dev, "inbound msg too big: (%d, %d)\n", len, msg_len);
return -EINVAL;
@@ -739,7 +739,7 @@ static int rpmsg_recv_single(struct virtproc_info *vrp, struct device *dev,
dev_warn_ratelimited(dev, "msg received with no recipient\n");
/* publish the real size of the buffer */
- rpmsg_sg_init(&sg, msg, vrp->buf_size);
+ rpmsg_sg_init(&sg, msg, vrp->rbuf_size);
/* add the buffer back to the remote processor's virtqueue */
err = virtqueue_add_inbuf(vrp->rvq, &sg, 1, msg, GFP_KERNEL);
@@ -888,9 +888,39 @@ static int rpmsg_probe(struct virtio_device *vdev)
else
vrp->num_sbufs = MAX_RPMSG_NUM_BUFS;
- vrp->buf_size = MAX_RPMSG_BUF_SIZE;
+ /*
+ * If VIRTIO_RPMSG_F_BUFSZ feature is supported, then configure buf
+ * size from virtio device config space from the resource table.
+ * If the feature is not supported, then assign default buf size.
+ */
+ if (virtio_has_feature(vdev, VIRTIO_RPMSG_F_BUFSZ)) {
+ /* note: virtio_rpmsg_config is defined from remote view */
+ virtio_cread(vdev, struct virtio_rpmsg_config,
+ txbuf_size, &vrp->rbuf_size);
+ virtio_cread(vdev, struct virtio_rpmsg_config,
+ rxbuf_size, &vrp->sbuf_size);
+
+ /* The buffers must hold rpmsg header atleast */
+ if (vrp->rbuf_size < sizeof(struct rpmsg_hdr) ||
+ vrp->sbuf_size < sizeof(struct rpmsg_hdr)) {
+ dev_err(&vdev->dev,
+ "vdev config: rx buf sz = %d, tx buf sz = %d\n",
+ vrp->rbuf_size, vrp->sbuf_size);
+ err = -EINVAL;
+ goto vqs_del;
+ }
+
+ dev_dbg(&vdev->dev,
+ "vdev config: rx buf sz = 0x%x, tx buf sz = 0x%x\n",
+ vrp->rbuf_size, vrp->sbuf_size);
+ } else {
+ vrp->rbuf_size = DEFAULT_RPMSG_BUF_SIZE;
+ vrp->sbuf_size = DEFAULT_RPMSG_BUF_SIZE;
+ }
- total_buf_space = (vrp->num_rbufs + vrp->num_sbufs) * vrp->buf_size;
+ total_buf_space = (vrp->num_rbufs * vrp->rbuf_size) +
+ (vrp->num_sbufs * vrp->sbuf_size);
+ total_buf_space = ALIGN(total_buf_space, PAGE_SIZE);
/* allocate coherent memory for the buffers */
bufs_va = dma_alloc_coherent(vdev->dev.parent,
@@ -908,14 +938,14 @@ static int rpmsg_probe(struct virtio_device *vdev)
vrp->rbufs = bufs_va;
/* and second part is dedicated for TX */
- vrp->sbufs = bufs_va + vrp->num_rbufs * vrp->buf_size;
+ vrp->sbufs = bufs_va + (vrp->num_rbufs * vrp->rbuf_size);
/* set up the receive buffers */
for (i = 0; i < vrp->num_rbufs; i++) {
struct scatterlist sg;
- void *cpu_addr = vrp->rbufs + i * vrp->buf_size;
+ void *cpu_addr = vrp->rbufs + i * vrp->rbuf_size;
- rpmsg_sg_init(&sg, cpu_addr, vrp->buf_size);
+ rpmsg_sg_init(&sg, cpu_addr, vrp->rbuf_size);
err = virtqueue_add_inbuf(vrp->rvq, &sg, 1, cpu_addr,
GFP_KERNEL);
@@ -1001,8 +1031,8 @@ static int rpmsg_remove_device(struct device *dev, void *data)
static void rpmsg_remove(struct virtio_device *vdev)
{
struct virtproc_info *vrp = vdev->priv;
- unsigned int num_bufs = vrp->num_rbufs + vrp->num_sbufs;
- size_t total_buf_space = num_bufs * vrp->buf_size;
+ size_t total_buf_space = (vrp->num_rbufs * vrp->rbuf_size) +
+ (vrp->num_sbufs * vrp->sbuf_size);
int ret;
virtio_reset_device(vdev);
@@ -1015,6 +1045,7 @@ static void rpmsg_remove(struct virtio_device *vdev)
vdev->config->del_vqs(vrp->vdev);
+ total_buf_space = ALIGN(total_buf_space, PAGE_SIZE);
dma_free_coherent(vdev->dev.parent, total_buf_space,
vrp->rbufs, vrp->bufs_dma);
@@ -1028,6 +1059,7 @@ static struct virtio_device_id id_table[] = {
static unsigned int features[] = {
VIRTIO_RPMSG_F_NS,
+ VIRTIO_RPMSG_F_BUFSZ,
};
static struct virtio_driver virtio_ipc_driver = {
diff --git a/include/linux/virtio_rpmsg.h b/include/linux/virtio_rpmsg.h
new file mode 100644
index 000000000000..6406bc505383
--- /dev/null
+++ b/include/linux/virtio_rpmsg.h
@@ -0,0 +1,24 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+/*
+ * Copyright (C) Pinecone Inc. 2019
+ * Copyright (C) Xiang Xiao <xiaoxiang@...econe.net>
+ */
+
+#ifndef _LINUX_VIRTIO_RPMSG_H
+#define _LINUX_VIRTIO_RPMSG_H
+
+#include <linux/types.h>
+
+/* The feature bitmap for virtio rpmsg */
+#define VIRTIO_RPMSG_F_NS 0 /* RP supports name service notifications */
+#define VIRTIO_RPMSG_F_BUFSZ 2 /* RP get buffer size from config space */
+
+struct virtio_rpmsg_config {
+ /* The tx/rx individual buffer size(if VIRTIO_RPMSG_F_BUFSZ) */
+ __u32 txbuf_size;
+ __u32 rxbuf_size;
+ __u32 reserved[14]; /* Reserve for the future use */
+ /* Put the customize config here */
+} __attribute__((packed));
+
+#endif /* _LINUX_VIRTIO_RPMSG_H */
--
2.34.1
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