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Tsirkin" To: Tanmay Shah Cc: Zhongqiu Han , andersson@kernel.org, mathieu.poirier@linaro.org, jasowang@redhat.com, xuanzhuo@linux.alibaba.com, eperezma@redhat.com, linux-kernel@vger.kernel.org, linux-remoteproc@vger.kernel.org, virtualization@lists.linux.dev, xiaoxiang@xiaomi.com, Xiang Xiao , arnaud.pouliquen@foss.st.com Subject: Re: [RFC PATCH 2/2] rpmsg: virtio_rpmsg_bus: get buffer size from config space Message-ID: <20251203142540-mutt-send-email-mst@kernel.org> References: <20251114184640.3020427-1-tanmay.shah@amd.com> <20251114184640.3020427-3-tanmay.shah@amd.com> <11280877-95f0-4361-9112-23bb17372e91@oss.qualcomm.com> Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: iqyHVY_GYxmWJf0MPTGBhk0WUUh6JZP3Z8J1Zo22Hms_1764790561 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit On Wed, Dec 03, 2025 at 12:12:46PM -0600, Tanmay Shah wrote: > Hello, > > Thanks for your reviews. Please find the response below. > > On 11/22/25 6:05 AM, Zhongqiu Han wrote: > > On 11/15/2025 2:46 AM, Tanmay Shah wrote: > > > From: Xiang Xiao > > > > > > 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 > > > Signed-off-by: Tanmay Shah > > > --- > > >   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 > > >   #include > > >   #include > > > +#include > > >   #include > > >   #include > > > @@ -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)) { > > > > > > Hello Tanmay, > > > > May I know if the omission of = here is to accommodate the ping/pong/ack > > scenarios? mtu will 0 > > > > > > Yes. At minimum RPMsg header is needed to ping the correct endpoint. We > don't need to have any payload attached to the packet. MTU will be sizeof > rpmsg_hdr I think. > > > > +            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 */ > > > > > > Echo Arnaud's comments. If it is intended for UAPI, please keep it in > > include/uapi/linux > > > > > > It's not intended for UAPI. I need to fix the license. I will check other > virtio headers in the same directory and fix the license accordingly. > > > > +/* > > > + * Copyright (C) Pinecone Inc. 2019 > > > + * Copyright (C) Xiang Xiao > > > + */ > > > + > > > +#ifndef _LINUX_VIRTIO_RPMSG_H > > > +#define _LINUX_VIRTIO_RPMSG_H > > > + > > > +#include > > > + > > > +/* 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 */ > > > > May I know why skip bit 1? > > > > > > Thanks, that's a good question. I keept id 2 unmodified from the original > series. I don't know why ID 2 was chosen in the original series. I will have > to discuss this with the linux remoteproc/rpmsg maintainers and choose the > correct ID. > > I don't see any problem choosing ID 1, but for some reason if ID 1 was > assigned and deprecated (I don't think that is the case) then only we should > use ID 2. > > > Arnaud, Mathieu, Bjorn any input here? > > > > + > > > +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 */ > > > > Should we use __virtio32 instead of __u32 to avoid endianness issues? > > > > > > Sure, if that is the standard in other virtio headers I will modify it. > > Thanks, > Tanmay rpmsg is still not standardized, sadly. It's really time it was. Modern virtio devices use __le32. Accordingly, accessed with virtio_cread_le __virtioXX and virtio_cread are for legacy compatible parts of config space. Does rpmsg want to be modern or keep using legacy? I donnu. Ideally it should finally be documented and at that point we definitely will want to switch to __le32. For now, run sparse to make sure you don't introduce new endian-ness issues. > > > +    /* Put the customize config here */ > > > +} __attribute__((packed)); > > > + > > > +#endif /* _LINUX_VIRTIO_RPMSG_H */ > > > >