On Fri, Jun 05, 2020 at 10:28:42AM +0900, David Stevens wrote:
On Fri, Jun 5, 2020 at 4:05 AM Michael S. Tsirkin mst@redhat.com wrote:
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 stevensd@chromium.org
Is this just for graphics? If yes I'd rather we put it in the graphics driver. We can always move it later ...
As stated in the cover letter, this will be used by virtio-video.
The proposed virtio-video patches: https://markmail.org/thread/p5d3k566srtdtute The patch which imports these dma-bufs (slightly out of data, uses v3 of this patch set): https://markmail.org/thread/j4xlqaaim266qpks
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 <linux/virtio_dma_buf.h>
+/**
- 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?
This approach provides a more explicit type signature and a little more type safety, I think. If others don't think it's a worthwhile tradeoff, I can remove it.
-David
The cost is that if dma_buf_export_info changes even slightly, we get weird crashes.