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[109.64.41.91]) by smtp.gmail.com with ESMTPSA id j190sm8467500wmb.33.2020.06.04.12.05.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 04 Jun 2020 12:05:27 -0700 (PDT) Date: Thu, 4 Jun 2020 15:05:23 -0400 From: "Michael S. Tsirkin" To: David Stevens Cc: Gerd Hoffmann , David Airlie , Daniel Vetter , Sumit Semwal , Jason Wang , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, virtualization@lists.linux-foundation.org, linux-media@vger.kernel.org, linaro-mm-sig@lists.linaro.org, virtio-dev@lists.oasis-open.org Subject: Re: [PATCH v4 1/3] virtio: add dma-buf support for exported objects Message-ID: <20200604145620-mutt-send-email-mst@kernel.org> References: <20200526105811.30784-1-stevensd@chromium.org> <20200526105811.30784-2-stevensd@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200526105811.30784-2-stevensd@chromium.org> Sender: linux-media-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org On Tue, May 26, 2020 at 07:58:09PM +0900, David Stevens wrote: > This change adds a new flavor of dma-bufs that can be used by virtio > drivers to share exported objects. A virtio dma-buf can be queried by > virtio drivers to obtain the UUID which identifies the underlying > exported object. > > Signed-off-by: David Stevens Is this just for graphics? If yes I'd rather we put it in the graphics driver. We can always move it later ... > --- > drivers/virtio/Makefile | 2 +- > drivers/virtio/virtio.c | 6 +++ > drivers/virtio/virtio_dma_buf.c | 89 +++++++++++++++++++++++++++++++++ > include/linux/virtio.h | 1 + > include/linux/virtio_dma_buf.h | 58 +++++++++++++++++++++ > 5 files changed, 155 insertions(+), 1 deletion(-) > create mode 100644 drivers/virtio/virtio_dma_buf.c > create mode 100644 include/linux/virtio_dma_buf.h > > diff --git a/drivers/virtio/Makefile b/drivers/virtio/Makefile > index 29a1386ecc03..ecdae5b596de 100644 > --- a/drivers/virtio/Makefile > +++ b/drivers/virtio/Makefile > @@ -1,5 +1,5 @@ > # SPDX-License-Identifier: GPL-2.0 > -obj-$(CONFIG_VIRTIO) += virtio.o virtio_ring.o > +obj-$(CONFIG_VIRTIO) += virtio.o virtio_ring.o virtio_dma_buf.o > obj-$(CONFIG_VIRTIO_MMIO) += virtio_mmio.o > obj-$(CONFIG_VIRTIO_PCI) += virtio_pci.o > virtio_pci-y := virtio_pci_modern.o virtio_pci_common.o > diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c > index a977e32a88f2..5d46f0ded92d 100644 > --- a/drivers/virtio/virtio.c > +++ b/drivers/virtio/virtio.c > @@ -357,6 +357,12 @@ int register_virtio_device(struct virtio_device *dev) > } > EXPORT_SYMBOL_GPL(register_virtio_device); > > +bool is_virtio_device(struct device *dev) > +{ > + return dev->bus == &virtio_bus; > +} > +EXPORT_SYMBOL_GPL(is_virtio_device); > + > void unregister_virtio_device(struct virtio_device *dev) > { > int index = dev->index; /* save for after device release */ > diff --git a/drivers/virtio/virtio_dma_buf.c b/drivers/virtio/virtio_dma_buf.c > new file mode 100644 > index 000000000000..23e3399b11ed > --- /dev/null > +++ b/drivers/virtio/virtio_dma_buf.c > @@ -0,0 +1,89 @@ > +// SPDX-License-Identifier: GPL-2.0-or-later > +/* > + * dma-bufs for virtio exported objects > + * > + * Copyright (C) 2020 Google, Inc. > + */ > + > +#include > + > +/** > + * virtio_dma_buf_export - Creates a new dma-buf for a virtio exported object > + * > + * This wraps dma_buf_export() to allow virtio drivers to create a dma-buf > + * for an virtio exported object that can be queried by other virtio drivers > + * for the object's UUID. > + */ > +struct dma_buf *virtio_dma_buf_export( > + const struct virtio_dma_buf_export_info *virtio_exp_info) > +{ > + struct dma_buf_export_info exp_info; > + > + if (!virtio_exp_info->ops > + || virtio_exp_info->ops->ops.attach != &virtio_dma_buf_attach > + || !virtio_exp_info->ops->get_uuid) { > + return ERR_PTR(-EINVAL); > + } > + > + exp_info.exp_name = virtio_exp_info->exp_name; > + exp_info.owner = virtio_exp_info->owner; > + exp_info.ops = &virtio_exp_info->ops->ops; > + exp_info.size = virtio_exp_info->size; > + exp_info.flags = virtio_exp_info->flags; > + exp_info.resv = virtio_exp_info->resv; > + exp_info.priv = virtio_exp_info->priv; > + BUILD_BUG_ON(sizeof(struct virtio_dma_buf_export_info) > + != sizeof(struct dma_buf_export_info)); This is the only part that gives me pause. Why do we need this hack? What's wrong with just using dma_buf_export_info directly, and if you want the virtio ops, just using container_off? > + > + return dma_buf_export(&exp_info); > +} > +EXPORT_SYMBOL(virtio_dma_buf_export); > + > +/** > + * virtio_dma_buf_attach - mandatory attach callback for virtio dma-bufs > + */ > +int virtio_dma_buf_attach(struct dma_buf *dma_buf, > + struct dma_buf_attachment *attach) > +{ > + int ret; > + const struct virtio_dma_buf_ops *ops = container_of( > + dma_buf->ops, const struct virtio_dma_buf_ops, ops); > + > + if (ops->device_attach) { > + ret = ops->device_attach(dma_buf, attach); > + if (ret) > + return ret; > + } > + return 0; > +} > +EXPORT_SYMBOL(virtio_dma_buf_attach); > + > +/** > + * is_virtio_dma_buf - returns true if the given dma-buf is a virtio dma-buf > + * @dma_buf: buffer to query > + */ > +bool is_virtio_dma_buf(struct dma_buf *dma_buf) > +{ > + return dma_buf->ops->attach == &virtio_dma_buf_attach; > +} > +EXPORT_SYMBOL(is_virtio_dma_buf); > + > +/** > + * virtio_dma_buf_get_uuid - gets the uuid of the virtio dma-buf's exported object > + * @dma_buf: [in] buffer to query > + * @uuid: [out] the uuid > + * > + * Returns: 0 on success, negative on failure. > + */ > +int virtio_dma_buf_get_uuid(struct dma_buf *dma_buf, > + uuid_t *uuid) > +{ > + const struct virtio_dma_buf_ops *ops = container_of( > + dma_buf->ops, const struct virtio_dma_buf_ops, ops); > + > + if (!is_virtio_dma_buf(dma_buf)) > + return -EINVAL; > + > + return ops->get_uuid(dma_buf, uuid); > +} > +EXPORT_SYMBOL(virtio_dma_buf_get_uuid); > diff --git a/include/linux/virtio.h b/include/linux/virtio.h > index 15f906e4a748..9397e25616c4 100644 > --- a/include/linux/virtio.h > +++ b/include/linux/virtio.h > @@ -128,6 +128,7 @@ static inline struct virtio_device *dev_to_virtio(struct device *_dev) > void virtio_add_status(struct virtio_device *dev, unsigned int status); > int register_virtio_device(struct virtio_device *dev); > void unregister_virtio_device(struct virtio_device *dev); > +bool is_virtio_device(struct device *dev); > > void virtio_break_device(struct virtio_device *dev); > > diff --git a/include/linux/virtio_dma_buf.h b/include/linux/virtio_dma_buf.h > new file mode 100644 > index 000000000000..29fee167afbd > --- /dev/null > +++ b/include/linux/virtio_dma_buf.h > @@ -0,0 +1,58 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > +/* > + * dma-bufs for virtio exported objects > + * > + * Copyright (C) 2020 Google, Inc. > + */ > + > +#ifndef _LINUX_VIRTIO_DMA_BUF_H > +#define _LINUX_VIRTIO_DMA_BUF_H > + > +#include > +#include > +#include > + > +/** > + * struct virtio_dma_buf_ops - operations possible on exported object dma-buf > + * @ops: the base dma_buf_ops. ops.attach MUST be virtio_dma_buf_attach. > + * @device_attach: [optional] callback invoked by virtio_dma_buf_attach during > + * all attach operations. > + * @get_uid: [required] callback to get the uuid of the exported object. > + */ > +struct virtio_dma_buf_ops { > + struct dma_buf_ops ops; > + int (*device_attach)(struct dma_buf *dma_buf, > + struct dma_buf_attachment *attach); > + int (*get_uuid)(struct dma_buf *dma_buf, uuid_t *uuid); > +}; > + > +/** > + * struct virtio_dma_buf_export_info - see struct dma_buf_export_info > + */ > +struct virtio_dma_buf_export_info { > + const char *exp_name; > + struct module *owner; > + const struct virtio_dma_buf_ops *ops; > + size_t size; > + int flags; > + struct dma_resv *resv; > + void *priv; > +}; > + > +/** > + * DEFINE_VIRTIO_DMA_BUF_EXPORT_INFO - helper macro for exporters > + */ > +#define DEFINE_VIRTIO_DMA_BUF_EXPORT_INFO(name) \ > + struct virtio_dma_buf_export_info name = { \ > + .exp_name = KBUILD_MODNAME, \ > + .owner = THIS_MODULE } > + > +int virtio_dma_buf_attach(struct dma_buf *dma_buf, > + struct dma_buf_attachment *attach); > + > +struct dma_buf *virtio_dma_buf_export( > + const struct virtio_dma_buf_export_info *virtio_exp_info); > +bool is_virtio_dma_buf(struct dma_buf *dma_buf); > +int virtio_dma_buf_get_uuid(struct dma_buf *dma_buf, uuid_t *uuid); > + > +#endif /* _LINUX_VIRTIO_DMA_BUF_H */ > -- > 2.27.0.rc0.183.gde8f92d652-goog