Re: [PATCH 3/3] rpmsg: virtio_rpmsg_bus: get buffer size from config space

[Arnaud Pouliquen <arnaud.pouliquen@st.com>]

Hello Xiang,

On 5/9/19 3:00 PM, xiang xiao wrote:
> On Thu, May 9, 2019 at 8:36 PM Arnaud Pouliquen <arnaud.pouliquen@st.com> wrote:
>>
>> Hello Xiang,
>>
>> Similar mechanism has been proposed by Loic 2 years ago (link to the
>> series here https://lkml.org/lkml/2017/3/28/349).
>>
>> Did you see them? Regarding history, patches seem just on hold...
>>
> 
> Just saw this patchset, so it's common problem hit by many vendor,
> rpmsg framework need to address it.:)
> 
>> Main differences (except interesting RX/TX size split) seems that you
>> - don't use the virtio_config_ops->get
> 
> virtio_cread call virtio_config_ops->get internally, the ideal is same
> for both patch, just the implementation detail is different.
> 
>> - define a new feature VIRTIO_RPMSG_F_NS.
> 
> I add this flag to keep the compatibility with old remote peer, and
> also follow the common virito driver practice.
I discussed with Loic, he is ok to go further with your patch and
abandon his one. Please find some remarks below in-line
> 
>>
>> Regards
>> Arnaud
>>
>>
>> On 1/31/19 4:41 PM, Xiang Xiao 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: Xiang Xiao <xiaoxiang@xiaomi.com>
>>> ---
>>>  drivers/rpmsg/virtio_rpmsg_bus.c  | 50 +++++++++++++++++++++++++--------------
>>>  include/uapi/linux/virtio_rpmsg.h | 24 +++++++++++++++++++
>>>  2 files changed, 56 insertions(+), 18 deletions(-)
>>>  create mode 100644 include/uapi/linux/virtio_rpmsg.h
>>>
>>> diff --git a/drivers/rpmsg/virtio_rpmsg_bus.c b/drivers/rpmsg/virtio_rpmsg_bus.c
>>> index 59c4554..049dd97 100644
>>> --- a/drivers/rpmsg/virtio_rpmsg_bus.c
>>> +++ b/drivers/rpmsg/virtio_rpmsg_bus.c
>>> @@ -16,6 +16,7 @@
>>>  #include <linux/virtio.h>
>>>  #include <linux/virtio_ids.h>
>>>  #include <linux/virtio_config.h>
>>> +#include <linux/virtio_rpmsg.h>
>>>  #include <linux/scatterlist.h>
>>>  #include <linux/dma-mapping.h>
>>>  #include <linux/slab.h>
>>> @@ -38,7 +39,8 @@
>>>   * @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
>>>   * @rbufs_dma:       dma base addr of rx buffers
>>>   * @sbufs_dma:       dma base addr of tx buffers
>>> @@ -61,7 +63,8 @@ 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 rbufs_dma;
>>>       dma_addr_t sbufs_dma;
>>> @@ -73,9 +76,6 @@ 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
>>> @@ -452,7 +452,7 @@ 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);
>>> @@ -578,7 +578,7 @@ 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;
>>>       }
>>> @@ -718,7 +718,7 @@ 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;
>>> @@ -751,7 +751,7 @@ static int rpmsg_recv_single(struct virtproc_info *vrp, struct device *dev,
>>>               dev_warn(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);
>>> @@ -907,11 +907,24 @@ static int rpmsg_probe(struct virtio_device *vdev)
>>>       else
>>>               vrp->num_sbufs = MAX_RPMSG_NUM_BUFS;
>>>
>>> -     vrp->buf_size = MAX_RPMSG_BUF_SIZE;
>>> +     /* try to get buffer size from config space */
>>> +     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);
>>> +     }
>>> +
>>> +     /* use the default if resource table doesn't provide one */
>>> +     if (!vrp->rbuf_size)
>>> +             vrp->rbuf_size = MAX_RPMSG_BUF_SIZE;
In this case constant should be renamed DEFAULT_RPMSG_BUF_SIZE as it is
no more a max value
>>> +     if (!vrp->sbuf_size)
>>> +             vrp->sbuf_size = MAX_RPMSG_BUF_SIZE;
Here, if the config space exists you need to update it in consequence to
ensure coherency with the remote processor config.

>>>
>>>       /* allocate coherent memory for the buffers */
>>>       vrp->rbufs = dma_alloc_coherent(vdev->dev.parent->parent,
>>> -                                     vrp->num_rbufs * vrp->buf_size,
>>> +                                     vrp->num_rbufs * vrp->rbuf_size,
>>>                                       &vrp->rbufs_dma, GFP_KERNEL);
>>>       if (!vrp->rbufs) {
>>>               err = -ENOMEM;
>>> @@ -922,7 +935,7 @@ static int rpmsg_probe(struct virtio_device *vdev)
>>>               vrp->rbufs, &vrp->rbufs_dma);
>>>
>>>       vrp->sbufs = dma_alloc_coherent(vdev->dev.parent->parent,
>>> -                                     vrp->num_sbufs * vrp->buf_size,
>>> +                                     vrp->num_sbufs * vrp->sbuf_size,
>>>                                       &vrp->sbufs_dma, GFP_KERNEL);
>>>       if (!vrp->sbufs) {
>>>               err = -ENOMEM;
>>> @@ -935,9 +948,9 @@ static int rpmsg_probe(struct virtio_device *vdev)
>>>       /* 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);
>>> @@ -984,11 +997,11 @@ static int rpmsg_probe(struct virtio_device *vdev)
>>>
>>>  free_sbufs:
>>>       dma_free_coherent(vdev->dev.parent->parent,
>>> -                       vrp->num_sbufs * vrp->buf_size,
>>> +                       vrp->num_sbufs * vrp->sbuf_size,
>>>                         vrp->sbufs, vrp->sbufs_dma);
>>>  free_rbufs:
>>>       dma_free_coherent(vdev->dev.parent->parent,
>>> -                       vrp->num_rbufs * vrp->buf_size,
>>> +                       vrp->num_rbufs * vrp->rbuf_size,
>>>                         vrp->rbufs, vrp->rbufs_dma);
>>>  vqs_del:
>>>       vdev->config->del_vqs(vrp->vdev);
>>> @@ -1023,10 +1036,10 @@ static void rpmsg_remove(struct virtio_device *vdev)
>>>       vdev->config->del_vqs(vrp->vdev);
>>>
>>>       dma_free_coherent(vdev->dev.parent->parent,
>>> -                       vrp->num_sbufs * vrp->buf_size,
>>> +                       vrp->num_sbufs * vrp->sbuf_size,
>>>                         vrp->sbufs, vrp->sbufs_dma);
>>>       dma_free_coherent(vdev->dev.parent->parent,
>>> -                       vrp->num_rbufs * vrp->buf_size,
>>> +                       vrp->num_rbufs * vrp->rbuf_size,
>>>                         vrp->rbufs, vrp->rbufs_dma);
>>>
>>>       kfree(vrp);
>>> @@ -1039,6 +1052,7 @@ 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/uapi/linux/virtio_rpmsg.h b/include/uapi/linux/virtio_rpmsg.h
>>> new file mode 100644
>>> index 0000000..24fa0dd
>>> --- /dev/null
>>> +++ b/include/uapi/linux/virtio_rpmsg.h
Strange to define a user space API for kernel usage need. Could you
elaborate?

>>> @@ -0,0 +1,24 @@
>>> +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
>>> +/*
>>> + * Copyright (C) Pinecone Inc. 2019
>>> + * Copyright (C) Xiang Xiao <xiaoxiang@pinecone.net>
>>> + */
>>> +
>>> +#ifndef _UAPI_LINUX_VIRTIO_RPMSG_H
>>> +#define _UAPI_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 */
Would be useful to document it in rpmsg.txt
>>> +
>>> +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));
>>> +
Wouldn't it be better to add an identifier and a version fields at the
beginning of the structure? Idea would be to simplify a future extension
In this case is VIRTIO_RPMSG_F_BUFSZ still useful?

>>> +#endif /* _UAPI_LINUX_VIRTIO_RPMSG_H */
>>>
--
Thanks
Arnaud