From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from canpmsgout11.his.huawei.com (canpmsgout11.his.huawei.com [113.46.200.226]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A9AE9367F5B; Wed, 6 May 2026 06:58:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=113.46.200.226 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778050733; cv=none; b=HjX2dY1N22/jib2V/i4wAuddnG+nLSWFm0ZaQI/E+JBPFu+kM40EuwSkkbTS+nGfkR1PnlonBefqMXzwFDZ1RueVRMqa0I3ZxipuQ5Pkk11ffV2gf5XDUi6F3NdTslO0bSRuLg12dfIKmtSrDUdhKZZadN5GEKhrufmSWKcZYog= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778050733; c=relaxed/simple; bh=sY5tng38gcB9d6yfv3moDi7zkrwX/tSnnQN2YfeTxTA=; h=Message-ID:Date:MIME-Version:Subject:To:CC:References:From: In-Reply-To:Content-Type; b=BuhEV6eG7C9Mj80QlK/CYRAC/9qmiZgwRfb1/bQ3rDChvMY6O4FVMQJDBGUQU2svq577hwFtkbfMwklMP6gcvfEVPSmhR+sDhb20mB90Cxer3oj9GWYSxb9f/n0kjA6zFlWRuU+StpbFuwug+pGsHZzTFXshNpW1riB7NPeiAqg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; dkim=pass (1024-bit key) header.d=huawei.com header.i=@huawei.com header.b=rY2rX3cL; arc=none smtp.client-ip=113.46.200.226 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=huawei.com header.i=@huawei.com header.b="rY2rX3cL" dkim-signature: v=1; a=rsa-sha256; d=huawei.com; s=dkim; c=relaxed/relaxed; q=dns/txt; h=From; bh=G+HgQJkz+cXLEu0vkzPQS/AfVAtum3DymBhzhdmqjVs=; b=rY2rX3cL84ykQx4bxmZDkhviFef06MCpPOpPN/6UkenY5nWH5h/U4p1LKj/2mpw0dC1/MB0HE hqH2vyo0WbUM5fEsGK7zR5cE6xmrv0anu8sHiIWRifN57edlqcXoCcY838w05MWV0kTMzsmw/qG u+PDj81kbdjK1hd/OUJbjwU= Received: from mail.maildlp.com (unknown [172.19.163.127]) by canpmsgout11.his.huawei.com (SkyGuard) with ESMTPS id 4g9QzT0pKszKm4C; Wed, 6 May 2026 14:52:05 +0800 (CST) Received: from kwepemk500009.china.huawei.com (unknown [7.202.194.94]) by mail.maildlp.com (Postfix) with ESMTPS id 1AEBB402AB; Wed, 6 May 2026 14:58:38 +0800 (CST) Received: from [10.67.121.161] (10.67.121.161) by kwepemk500009.china.huawei.com (7.202.194.94) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Wed, 6 May 2026 14:58:37 +0800 Message-ID: <09995589-b81d-4cb7-a313-15a943d8b28d@huawei.com> Date: Wed, 6 May 2026 14:58:36 +0800 Precedence: bulk X-Mailing-List: linux-pci@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/2] vfio: add dma-buf get_tph callback and DMA_BUF_TPH feature To: Zhiping Zhang , Alex Williamson , Jason Gunthorpe , Leon Romanovsky CC: Bjorn Helgaas , , , , , Keith Busch , Yochai Cohen , Yishai Hadas References: <20260430200704.352228-1-zhipingz@meta.com> <20260430200704.352228-2-zhipingz@meta.com> Content-Language: en-US From: fengchengwen In-Reply-To: <20260430200704.352228-2-zhipingz@meta.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-ClientProxiedBy: kwepems200002.china.huawei.com (7.221.188.68) To kwepemk500009.china.huawei.com (7.202.194.94) On 5/1/2026 4:06 AM, Zhiping Zhang wrote: > Add a dma-buf callback that returns raw TPH metadata from the exporter > so peer devices can reuse the steering tag and processing hint > associated with a VFIO-exported buffer. > > Add a new VFIO_DEVICE_FEATURE_DMA_BUF_TPH ioctl that takes the fd from > VFIO_DEVICE_FEATURE_DMA_BUF along with a steering tag and processing > hint, validates the fd is a vfio-exported dma-buf belonging to this > device, and stores the TPH values under memory_lock. This keeps the > existing VFIO_DEVICE_FEATURE_DMA_BUF uAPI completely unchanged. > > The user sequences setting TPH on the dma-buf before the importer > consumes it. > > Add an st_width parameter to get_tph() so the exporter can reject > steering tags that exceed the consumer's supported width (8 vs 16 bit). > When no TPH metadata was supplied, get_tph() returns -EOPNOTSUPP. > > Signed-off-by: Zhiping Zhang > > diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c > --- a/drivers/vfio/pci/vfio_pci_core.c > +++ b/drivers/vfio/pci/vfio_pci_core.c > @@ -1534,6 +1534,9 @@ int vfio_pci_core_ioctl_feature(struct vfio_device *device, u32 flags, > return vfio_pci_core_feature_token(vdev, flags, arg, argsz); > case VFIO_DEVICE_FEATURE_DMA_BUF: > return vfio_pci_core_feature_dma_buf(vdev, flags, arg, argsz); > + case VFIO_DEVICE_FEATURE_DMA_BUF_TPH: > + return vfio_pci_core_feature_dma_buf_tph(vdev, flags, arg, > + argsz); > default: > return -ENOTTY; > } > diff --git a/drivers/vfio/pci/vfio_pci_dmabuf.c b/drivers/vfio/pci/vfio_pci_dmabuf.c > --- a/drivers/vfio/pci/vfio_pci_dmabuf.c > +++ b/drivers/vfio/pci/vfio_pci_dmabuf.c > @@ -19,6 +19,9 @@ struct vfio_pci_dma_buf { > u32 nr_ranges; > struct kref kref; > struct completion comp; > + u16 steering_tag; > + u8 ph; > + u8 tph_present : 1; > u8 revoked : 1; > }; > > @@ -69,6 +72,22 @@ vfio_pci_dma_buf_map(struct dma_buf_attachment *attachment, > return ret; > } > > +static int vfio_pci_dma_buf_get_tph(struct dma_buf *dmabuf, u16 *steering_tag, > + u8 *ph, u8 st_width) > +{ > + struct vfio_pci_dma_buf *priv = dmabuf->priv; > + > + if (!priv->tph_present) > + return -EOPNOTSUPP; > + > + if (st_width < 16 && priv->steering_tag > ((1U << st_width) - 1)) > + return -EINVAL; The checker will failed in following cases: 1. If the exporter passed 8bit st, and importer support 16bit st, then it will pass the checker. 2. The exporter enabled 16bit st and its st is < 256 (note: the pcie protocol doesn't restrict 16bit-st must >=256), and importer only support 8bit st, then it will also pass the checker Suggest userspace passing both st(8bit) and extend-st(16bit), and importer chose the right one. > + > + *steering_tag = priv->steering_tag; > + *ph = priv->ph; > + return 0; > +} > + > static void vfio_pci_dma_buf_unmap(struct dma_buf_attachment *attachment, > struct sg_table *sgt, > enum dma_data_direction dir) > @@ -101,6 +120,7 @@ static void vfio_pci_dma_buf_release(struct dma_buf *dmabuf) > > static const struct dma_buf_ops vfio_pci_dmabuf_ops = { > .attach = vfio_pci_dma_buf_attach, > + .get_tph = vfio_pci_dma_buf_get_tph, > .map_dma_buf = vfio_pci_dma_buf_map, > .unmap_dma_buf = vfio_pci_dma_buf_unmap, > .release = vfio_pci_dma_buf_release, > @@ -331,6 +351,55 @@ int vfio_pci_core_feature_dma_buf(struct vfio_pci_core_device *vdev, u32 flags, > return ret; > } > > +int vfio_pci_core_feature_dma_buf_tph(struct vfio_pci_core_device *vdev, > + u32 flags, > + struct vfio_device_feature_dma_buf_tph __user *arg, > + size_t argsz) > +{ > + struct vfio_device_feature_dma_buf_tph set_tph; > + struct vfio_pci_dma_buf *priv; > + struct dma_buf *dmabuf; > + int ret; > + > + ret = vfio_check_feature(flags, argsz, VFIO_DEVICE_FEATURE_SET, > + sizeof(set_tph)); > + if (ret != 1) > + return ret; > + > + if (copy_from_user(&set_tph, arg, sizeof(set_tph))) > + return -EFAULT; > + > + if (set_tph.reserved) > + return -EINVAL; > + > + dmabuf = dma_buf_get(set_tph.dmabuf_fd); > + if (IS_ERR(dmabuf)) > + return PTR_ERR(dmabuf); > + > + if (dmabuf->ops != &vfio_pci_dmabuf_ops) { > + ret = -EINVAL; > + goto out_put; > + } > + > + priv = dmabuf->priv; > + down_write(&vdev->memory_lock); > + if (priv->vdev != vdev) { > + ret = -EINVAL; > + goto out_unlock; > + } > + > + priv->steering_tag = set_tph.steering_tag; > + priv->ph = set_tph.ph; > + priv->tph_present = 1; > + ret = 0; > + > +out_unlock: > + up_write(&vdev->memory_lock); > +out_put: > + dma_buf_put(dmabuf); > + return ret; > +} > + > void vfio_pci_dma_buf_move(struct vfio_pci_core_device *vdev, bool revoked) > { > struct vfio_pci_dma_buf *priv; > diff --git a/drivers/vfio/pci/vfio_pci_priv.h b/drivers/vfio/pci/vfio_pci_priv.h > --- a/drivers/vfio/pci/vfio_pci_priv.h > +++ b/drivers/vfio/pci/vfio_pci_priv.h > @@ -118,6 +118,10 @@ static inline bool vfio_pci_is_vga(struct pci_dev *pdev) > int vfio_pci_core_feature_dma_buf(struct vfio_pci_core_device *vdev, u32 flags, > struct vfio_device_feature_dma_buf __user *arg, > size_t argsz); > +int vfio_pci_core_feature_dma_buf_tph(struct vfio_pci_core_device *vdev, > + u32 flags, > + struct vfio_device_feature_dma_buf_tph __user *arg, > + size_t argsz); > void vfio_pci_dma_buf_cleanup(struct vfio_pci_core_device *vdev); > void vfio_pci_dma_buf_move(struct vfio_pci_core_device *vdev, bool revoked); > #else > @@ -128,6 +132,13 @@ vfio_pci_core_feature_dma_buf(struct vfio_pci_core_device *vdev, u32 flags, > { > return -ENOTTY; > } > +static inline int > +vfio_pci_core_feature_dma_buf_tph(struct vfio_pci_core_device *vdev, u32 flags, > + struct vfio_device_feature_dma_buf_tph __user *arg, > + size_t argsz) > +{ > + return -ENOTTY; > +} > static inline void vfio_pci_dma_buf_cleanup(struct vfio_pci_core_device *vdev) > { > } > diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h > --- a/include/linux/dma-buf.h > +++ b/include/linux/dma-buf.h > @@ -113,6 +113,23 @@ struct dma_buf_ops { > */ > void (*unpin)(struct dma_buf_attachment *attach); > > + /** > + * @get_tph: > + * @dmabuf: DMA buffer for which to retrieve TPH metadata > + * @steering_tag: Returns the raw TPH steering tag > + * @ph: Returns the TPH processing hint > + * @st_width: Consumer's supported steering tag width in bits (8 or 16) > + * > + * Return the TPH (TLP Processing Hints) metadata associated with this > + * DMA buffer. Exporters that do not provide TPH metadata should return > + * -EOPNOTSUPP. If the steering tag exceeds @st_width bits, return > + * -EINVAL. > + * > + * This callback is optional. > + */ > + int (*get_tph)(struct dma_buf *dmabuf, u16 *steering_tag, u8 *ph, > + u8 st_width); > + > /** > * @map_dma_buf: > * > diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h > --- a/include/uapi/linux/vfio.h > +++ b/include/uapi/linux/vfio.h > @@ -1534,6 +1534,28 @@ struct vfio_device_feature_dma_buf { > */ > #define VFIO_DEVICE_FEATURE_MIG_PRECOPY_INFOv2 12 > > +/** > + * Upon VFIO_DEVICE_FEATURE_SET associate TPH (TLP Processing Hints) metadata > + * with a vfio-exported dma-buf. The dma-buf must have been created by > + * VFIO_DEVICE_FEATURE_DMA_BUF on this device. > + * > + * dmabuf_fd is the file descriptor returned by VFIO_DEVICE_FEATURE_DMA_BUF. > + * steering_tag and ph are the raw TPH values that importing drivers should use > + * when accessing the buffer. > + * > + * The user must set TPH on the dma-buf before the importer consumes it. > + * > + * Return: 0 on success, -errno on failure. > + */ > +#define VFIO_DEVICE_FEATURE_DMA_BUF_TPH 13 > + > +struct vfio_device_feature_dma_buf_tph { > + __s32 dmabuf_fd; > + __u16 steering_tag; > + __u8 ph; > + __u8 reserved; > +}; > + > /* -------- API for Type1 VFIO IOMMU -------- */ > > /** > >