[virtio-dev] Re: [PATCH v4 1/3] virtio: add dma-buf support for exported objects
Hi David,
On Fri, Jun 19, 2020 at 10:57:37AM +0900, David Stevens wrote:
> On Thu, Jun 18, 2020 at 9:29 PM Guennadi Liakhovetski
> wrote:
> >
> > Hi Michael,
> >
> > On Thu, Jun 04, 2020 at 03:05:23PM -0400, Michael S. Tsirkin 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
> > >
> > > Is this just for graphics? If yes I'd rather we put it in the graphics
> > > driver. We can always move it later ...
> >
> > Wouldn't this be the API that audio virtualisation will have to use to share
> > buffers between the host and any guests?
>
> The new flavor of dma-buf isn't directly related to sharing buffers
> between the host and the guest. The purpose of this API is to help
> share buffers between multiple virtio devices - e.g. share buffers
> created by a virito-gpu device with a virito-video device. In
> particular, the new flavor of dma-buf provides a mechanism to attach
> identifying metadata to a dma-buf object that is shared between
> different virtio drivers in a single guest. This identifying metadata
> can then be passed to the importing device and used to fetch some
> resource from the exporting device. But the new flavor of dma-buf is
> an abstraction within the guest kernel, independent of the host-guest
> boundary, and it's definitely not necessary if we're only talking
> about a single virtio subsystem.
Thanks for the explanation!
Regards
Guennadi
> > > > ---
> > > > 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 == _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 ..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 !=
> > > > _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 = _exp_info->ops->ops;
> > > > + exp_info.size = virtio_exp_info->size;
> > > > + exp_info.flags = virtio_exp_info->flags;
> > > > +
[virtio-dev] Re: [PATCH v4 1/3] virtio: add dma-buf support for exported objects
On Thu, Jun 18, 2020 at 9:29 PM Guennadi Liakhovetski
wrote:
>
> Hi Michael,
>
> On Thu, Jun 04, 2020 at 03:05:23PM -0400, Michael S. Tsirkin 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
> >
> > Is this just for graphics? If yes I'd rather we put it in the graphics
> > driver. We can always move it later ...
>
> Wouldn't this be the API that audio virtualisation will have to use to share
> buffers between the host and any guests?
The new flavor of dma-buf isn't directly related to sharing buffers
between the host and the guest. The purpose of this API is to help
share buffers between multiple virtio devices - e.g. share buffers
created by a virito-gpu device with a virito-video device. In
particular, the new flavor of dma-buf provides a mechanism to attach
identifying metadata to a dma-buf object that is shared between
different virtio drivers in a single guest. This identifying metadata
can then be passed to the importing device and used to fetch some
resource from the exporting device. But the new flavor of dma-buf is
an abstraction within the guest kernel, independent of the host-guest
boundary, and it's definitely not necessary if we're only talking
about a single virtio subsystem.
-David
> Thanks
> Guennadi
>
> > > ---
> > > 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 == _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 ..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 != _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 = _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
[virtio-dev] Re: [PATCH v4 1/3] virtio: add dma-buf support for exported objects
Hi Michael,
On Thu, Jun 04, 2020 at 03:05:23PM -0400, Michael S. Tsirkin 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
>
> Is this just for graphics? If yes I'd rather we put it in the graphics
> driver. We can always move it later ...
Wouldn't this be the API that audio virtualisation will have to use to share
buffers between the host and any guests?
Thanks
Guennadi
> > ---
> > 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 == _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 ..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 != _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 = _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(_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-dev] Re: [PATCH v4 1/3] virtio: add dma-buf support for exported objects
On Mon, Jun 8, 2020 at 6:05 PM Michael S. Tsirkin wrote:
>
> On Mon, Jun 08, 2020 at 05:32:26PM +0900, David Stevens wrote:
> > On Mon, Jun 8, 2020 at 3:00 PM Michael S. Tsirkin wrote:
> > >
> > > On Mon, Jun 08, 2020 at 10:33:09AM +0900, David Stevens wrote:
> > > > On Sun, Jun 7, 2020 at 5:04 AM Michael S. Tsirkin
> > > > wrote:
> > > > >
> > > > > 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
> > > > > > 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
> > > > > > >
> > > > > > > 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 == _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 ..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-dev] Re: [PATCH v4 1/3] virtio: add dma-buf support for exported objects
On Mon, Jun 08, 2020 at 05:32:26PM +0900, David Stevens wrote:
> On Mon, Jun 8, 2020 at 3:00 PM Michael S. Tsirkin wrote:
> >
> > On Mon, Jun 08, 2020 at 10:33:09AM +0900, David Stevens wrote:
> > > On Sun, Jun 7, 2020 at 5:04 AM Michael S. Tsirkin wrote:
> > > >
> > > > 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
> > > > > 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
> > > > > >
> > > > > > 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 == _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 ..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 !=
> > > > > > > _dma_buf_attach
> > > > > > > + || !virtio_exp_info->ops->get_uuid) {
> > > > > > > + return ERR_PTR(-EINVAL);
> > > > > > > + }
> > > > > > > +
> > > > > > > + exp_info.exp_name = virtio_exp_info->exp_name;
> > > > > > > +
[virtio-dev] Re: [PATCH v4 1/3] virtio: add dma-buf support for exported objects
On Mon, Jun 08, 2020 at 10:33:09AM +0900, David Stevens wrote:
> On Sun, Jun 7, 2020 at 5:04 AM Michael S. Tsirkin wrote:
> >
> > 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 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
> > > >
> > > > 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 == _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 ..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 !=
> > > > > _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 = _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
[virtio-dev] Re: [PATCH v4 1/3] virtio: add dma-buf support for exported objects
On Sun, Jun 7, 2020 at 5:04 AM Michael S. Tsirkin wrote:
>
> 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 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
> > >
> > > 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 == _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 ..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 !=
> > > > _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 = _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
[virtio-dev] Re: [PATCH v4 1/3] virtio: add dma-buf support for exported objects
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 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
> >
> > 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 == _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 ..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 !=
> > > _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 = _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.
--
MST
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[virtio-dev] Re: [PATCH v4 1/3] virtio: add dma-buf support for exported objects
On Fri, Jun 5, 2020 at 4:05 AM Michael S. Tsirkin 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
>
> 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 == _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 ..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 != _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 = _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
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