On 5/20/2026 2:44 AM, Arnaud POULIQUEN wrote:
>
>
> On 5/19/26 19:36, Mathieu Poirier wrote:
>> On Wed, Apr 29, 2026 at 09:10:52AM -0700, Tanmay Shah wrote:
>>> 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: Tanmay Shah <[email protected]>
>>> ---
>>>
>>> Test done:
>>> - Verify this patch works with the existing firmware
>>> - Verify this patch works with the firmware that configures
>>> differt tx & rx buf size
>>>
>>> Changes in v2:
>>> - %s/sbuf_size/tx_buf_size/
>>> - %s/rbuf_size/rx_buf_size/
>>> - fix typo
>>> - do not use ALIGN on buf size, rely on allocator
>>> - make err msg more explicit, %s/vdev config:/bad vdev config/
>>> - fix license and add AMD copyrights in the header virtio_rpmsg.h
>>> - Assign bit 1 to VIRTIO_RPMSG_F_BUFSZ feature
>>> - use __virtio32 over __u32
>>> - add version field to virtio rpmsg config structure
>>> - move linux/virtio_rpmsg.h to linux/rpmsg/virtio_rpmsg.h
>>>
>>> drivers/rpmsg/virtio_rpmsg_bus.c | 70 ++++++++++++++++++++++--------
>>> include/linux/rpmsg/virtio_rpmsg.h | 27 ++++++++++++
>>> 2 files changed, 79 insertions(+), 18 deletions(-)
>>> create mode 100644 include/linux/rpmsg/virtio_rpmsg.h
>>>
>>> diff --git a/drivers/rpmsg/virtio_rpmsg_bus.c b/drivers/rpmsg/
>>> virtio_rpmsg_bus.c
>>> index e59d8cf9b975..8116d94413cc 100644
>>> --- a/drivers/rpmsg/virtio_rpmsg_bus.c
>>> +++ b/drivers/rpmsg/virtio_rpmsg_bus.c
>>> @@ -20,6 +20,7 @@
>>> #include <linux/rpmsg.h>
>>> #include <linux/rpmsg/byteorder.h>
>>> #include <linux/rpmsg/ns.h>
>>> +#include <linux/rpmsg/virtio_rpmsg.h>
>>> #include <linux/scatterlist.h>
>>> #include <linux/slab.h>
>>> #include <linux/sched.h>
>>> @@ -39,7 +40,8 @@
>>> * @tx_bufs: kernel address of tx buffers
>>> * @num_rx_buf: total number of buffers for rx
>>> * @num_tx_buf: total number of buffers for tx
>>> - * @buf_size: size of one rx or tx buffer
>>> + * @rx_buf_size: size of one rx buffer
>>> + * @tx_buf_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 and tx_bufs, to allow concurrent senders.
>>> @@ -59,7 +61,8 @@ struct virtproc_info {
>>> void *rx_bufs, *tx_bufs;
>>> unsigned int num_rx_buf;
>>> unsigned int num_tx_buf;
>>> - unsigned int buf_size;
>>> + unsigned int rx_buf_size;
>>> + unsigned int tx_buf_size;
>>> int last_sbuf;
>>> dma_addr_t bufs_dma;
>>> struct mutex tx_lock;
>>> @@ -68,9 +71,6 @@ struct virtproc_info {
>>> wait_queue_head_t sendq;
>>> };
>>> -/* 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
>>> @@ -128,7 +128,7 @@ 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.
>>> @@ -444,7 +444,7 @@ static void *get_a_tx_buf(struct virtproc_info *vrp)
>>> /* either pick the next unused tx buffer */
>>> if (vrp->last_sbuf < vrp->num_tx_buf)
>>> - ret = vrp->tx_bufs + vrp->buf_size * vrp->last_sbuf++;
>>> + ret = vrp->tx_bufs + vrp->tx_buf_size * vrp->last_sbuf++;
>>> /* or recycle a used one */
>>> else
>>> ret = virtqueue_get_buf(vrp->svq, &len);
>>> @@ -514,7 +514,7 @@ 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->tx_buf_size - sizeof(struct rpmsg_hdr)) {
>>> dev_err(dev, "message is too big (%d)\n", len);
>>> return -EMSGSIZE;
>>> }
>>> @@ -647,7 +647,7 @@ 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->tx_buf_size - sizeof(struct rpmsg_hdr);
>>> }
>>> static int rpmsg_recv_single(struct virtproc_info *vrp, struct
>>> device *dev,
>>> @@ -673,7 +673,7 @@ 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->rx_buf_size ||
>>> msg_len > (len - sizeof(struct rpmsg_hdr))) {
>>> dev_warn(dev, "inbound msg too big: (%d, %d)\n", len,
>>> msg_len);
>>> return -EINVAL;
>>> @@ -706,7 +706,7 @@ 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->rx_buf_size);
>>> /* add the buffer back to the remote processor's virtqueue */
>>> err = virtqueue_add_inbuf(vrp->rvq, &sg, 1, msg, GFP_KERNEL);
>>> @@ -824,6 +824,7 @@ static int rpmsg_probe(struct virtio_device *vdev)
>>> int err = 0, i;
>>> size_t total_buf_space;
>>> bool notify;
>>> + u16 version;
>>> vrp = kzalloc_obj(*vrp);
>>> if (!vrp)
>>> @@ -855,9 +856,41 @@ static int rpmsg_probe(struct virtio_device *vdev)
>>> else
>>> vrp->num_tx_buf = 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 */
>>> + version = 0;
>>> + virtio_cread(vdev, struct virtio_rpmsg_config,
>>> + version, &version);
>>> + virtio_cread(vdev, struct virtio_rpmsg_config,
>>> + txbuf_size, &vrp->rx_buf_size);
>>> + virtio_cread(vdev, struct virtio_rpmsg_config,
>>> + rxbuf_size, &vrp->tx_buf_size);
>>> +
>>
>> A check is also needed to make sure the version received from the
>> resource table
>> is '0'.
I think we should start with versaion = 1. So, can I check the version
number for 1 ?
>>
>>> + /* The buffers must hold at least the rpmsg header */
>>> + if (vrp->rx_buf_size < sizeof(struct rpmsg_hdr) ||
>>> + vrp->tx_buf_size < sizeof(struct rpmsg_hdr)) {
>>> + dev_err(&vdev->dev,
>>> + "bad vdev config: rx buf sz = %d, tx buf sz = %d\n",
>>> + vrp->rx_buf_size, vrp->tx_buf_size);
>>> + err = -EINVAL;
>>> + goto vqs_del;
>>> + }
>>> +
>>> + dev_dbg(&vdev->dev,
>>> + "vdev config: version=%d, rx buf sz = 0x%x, tx buf sz =
>>> 0x%x\n",
>>> + version, vrp->rx_buf_size, vrp->tx_buf_size);
>>> + } else {
>>> + vrp->rx_buf_size = DEFAULT_RPMSG_BUF_SIZE;
>>> + vrp->tx_buf_size = DEFAULT_RPMSG_BUF_SIZE;
>>> + }
>>> - total_buf_space = (vrp->num_rx_buf + vrp->num_tx_buf) * vrp-
>>> >buf_size;
>>> + total_buf_space = (vrp->num_rx_buf * vrp->rx_buf_size) +
>>> + (vrp->num_tx_buf * vrp->tx_buf_size);
>>> /* allocate coherent memory for the buffers */
>>> bufs_va = dma_alloc_coherent(vdev->dev.parent,
>>> @@ -875,14 +908,14 @@ static int rpmsg_probe(struct virtio_device *vdev)
>>> vrp->rx_bufs = bufs_va;
>>> /* and second part is dedicated for TX */
>>> - vrp->tx_bufs = bufs_va + vrp->num_rx_buf * vrp->buf_size;
>>> + vrp->tx_bufs = bufs_va + (vrp->num_rx_buf * vrp->rx_buf_size);
>>> /* set up the receive buffers */
>>> for (i = 0; i < vrp->num_rx_buf; i++) {
>>> struct scatterlist sg;
>>> - void *cpu_addr = vrp->rx_bufs + i * vrp->buf_size;
>>> + void *cpu_addr = vrp->rx_bufs + i * vrp->rx_buf_size;
>>> - rpmsg_sg_init(&sg, cpu_addr, vrp->buf_size);
>>> + rpmsg_sg_init(&sg, cpu_addr, vrp->rx_buf_size);
>>> err = virtqueue_add_inbuf(vrp->rvq, &sg, 1, cpu_addr,
>>> GFP_KERNEL);
>>> @@ -965,8 +998,8 @@ 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_rx_buf + vrp->num_tx_buf;
>>> - size_t total_buf_space = num_bufs * vrp->buf_size;
>>> + size_t total_buf_space = (vrp->num_rx_buf * vrp->rx_buf_size) +
>>> + (vrp->num_tx_buf * vrp->tx_buf_size);
>>> int ret;
>>> virtio_reset_device(vdev);
>>> @@ -992,6 +1025,7 @@ 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/rpmsg/virtio_rpmsg.h b/include/linux/
>>> rpmsg/virtio_rpmsg.h
>>> new file mode 100644
>>> index 000000000000..285918be68b9
>>> --- /dev/null
>>> +++ b/include/linux/rpmsg/virtio_rpmsg.h
>>> @@ -0,0 +1,27 @@
>>> +/* SPDX-License-Identifier: GPL-2.0 */
>>> +/*
>>> + * Copyright (C) Pinecone Inc. 2019
>>> + * Copyright (C) Xiang Xiao <[email protected]>
>>> + * Copyright (C) Advanced Micro Devices, Inc.
>>> + */
>>> +
>>> +#ifndef _LINUX_VIRTIO_RPMSG_H
>>> +#define _LINUX_VIRTIO_RPMSG_H
>>> +
>>> +#include <linux/types.h>
>>> +#include <linux/virtio_types.h>
>>> +
>>> +/* The feature bitmap for virtio rpmsg */
>>> +#define VIRTIO_RPMSG_F_NS 0 /* RP supports name service
>>> notifications */
>>> +#define VIRTIO_RPMSG_F_BUFSZ 1 /* RP get buffer size from config
>>> space */
>>> +
>>> +struct virtio_rpmsg_config {
>>> + __virtio16 version;
>>> + /* The tx/rx individual buffer size(if VIRTIO_RPMSG_F_BUFSZ) */
>>> + __virtio32 txbuf_size;
>>> + __virtio32 rxbuf_size;
>>> + __virtio32 reserved[14]; /* Reserve for the future use */
>>
>> 66 byte for the configuratio space? I'm puzzled about the
>> reserved[14], how did
>> you come up with that number?
I kept the reserved bytes from the original series as it is. The
original series did not contain version field. With version I don't
think we need reserved field at all. At best, if we want to append
padding bytes, then I think __virtio16 reserved; makes sense. That will
make the structure aligned to 4 byte.
>
> Is it useful to define the reserved field?
I think reserved field is only useful to keep the structure size aligned
to 4 bytes.
> The version should allow us to determine the content.
Correct, but I think the structure can be aligned if used correct
reserved bytes.
> An other solution is to introduce a'size' field to determine the size of
> the structure:
I think, the resource table already contains config_len field which is
size of the structure:
https://github.com/torvalds/linux/blob/27fa82620cbaa89a7fc11ac3057701d598813e87/include/linux/remoteproc.h#L275
> struct virtio_rpmsg_config {
> __virtio16 version;
> __virtio16 size; /* size of the configuration space */
> /* The tx/rx individual buffer size(if VIRTIO_RPMSG_F_BUFSZ) */
> __virtio32 txbuf_size;
> __virtio32 rxbuf_size;
> __u8 private[0]; /* customized config */
Do we need customized config? I think I should remove this comment from
the original patch as well.
Thanks,
Tanmay
> };
>
>>
>> The rest looks good to me.
>>
>
> Looks good to me too.
>
> Thanks,
> Arnaud
>
>>> + /* Put the customize config here */
>>> +} __packed;
>>> +
>>> +#endif /* _LINUX_VIRTIO_RPMSG_H */
>>> --
>>> 2.34.1
>>>
>
