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client-ip=165.204.84.17; helo=satlexmb07.amd.com; pr=C Received: from satlexmb07.amd.com (165.204.84.17) by DS3PEPF000099D3.mail.protection.outlook.com (10.167.17.4) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9388.8 via Frontend Transport; Wed, 3 Dec 2025 18:00:43 +0000 Received: from satlexmb07.amd.com (10.181.42.216) by satlexmb07.amd.com (10.181.42.216) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.17; Wed, 3 Dec 2025 12:00:42 -0600 Received: from [172.31.132.204] (10.180.168.240) by satlexmb07.amd.com (10.181.42.216) with Microsoft SMTP Server id 15.2.2562.17 via Frontend Transport; Wed, 3 Dec 2025 10:00:42 -0800 Message-ID: <65e5ba1e-c846-469a-a6e0-b63441da8cfa@amd.com> Date: Wed, 3 Dec 2025 12:00:41 -0600 Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Reply-To: Subject: Re: [RFC PATCH 2/2] rpmsg: virtio_rpmsg_bus: get buffer size from config space To: Arnaud POULIQUEN , , , , , , CC: , , , , Xiang Xiao References: <20251114184640.3020427-1-tanmay.shah@amd.com> <20251114184640.3020427-3-tanmay.shah@amd.com> <0a2b9fe6-d8b2-42d6-b6b3-9a94a82c6738@foss.st.com> Content-Language: en-US From: Tanmay Shah In-Reply-To: <0a2b9fe6-d8b2-42d6-b6b3-9a94a82c6738@foss.st.com> Content-Type: text/plain; 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X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 03 Dec 2025 18:00:43.5235 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 0b1e35ad-a653-47a1-3856-08de3295e0c9 X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[satlexmb07.amd.com] X-MS-Exchange-CrossTenant-AuthSource: DS3PEPF000099D3.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH0PR12MB7862 On 11/21/25 3:44 AM, Arnaud POULIQUEN wrote: > > > On 11/14/25 19:46, 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 */ > > typo:  /* The buffers must hold at least the rpmsg header */ Ack. >> +        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", > > message could be more explicit: s/"vdev config:/"bad vdev config:/ > Ack. >> +                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); > > Needed? The allocator does not manage the page alignment? > Ack. Not needed. Now as you pointed, I think it's better to leave the alignment to the allocator. This will be fixed. >>       /* 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 */ > > This licensing seems reserved for the UAPIs > Ack. I will check other headers in the same directory and update 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 */ >> + >> +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)); > > I am still convinced that adding a version field would help with future > improvements, even though a feature bit field can be used to handle new > configurations. Indeed, how can we address the need for more space > beyond the 14 reserved words? > Thanks, > Arnaud > Ack. Okay, it's not a deal breaker for me. I will add the version field linux side. I will add new structure in open-amp side as well accordingly. >> + >> +#endif /* _LINUX_VIRTIO_RPMSG_H */ >