Re: [PATCH v3 2/3] drivers: platform: goldfish: goldfish_address_space: add a driver

[Greg KH <gregkh@linuxfoundation.org>]

On Tue, Jan 08, 2019 at 06:11:11PM -0800, rkir@google.com wrote:
> From: Roman Kiryanov <rkir@google.com>
> 
> A driver for the Goldfish Android emulator that occupies
> address space to use it with the memory sharing device
> on the QEMU side. The memory sharding device allocates
> subranges and populate them with actual RAM.
> This allows sharing host's memory with the guest.
> 
> Signed-off-by: Roman Kiryanov <rkir@google.com>
> ---
> Changes in v3:
>  - No changes.
> 
> Changes in v2:
>  - Removed WARN_ON.
>  - Moved to drivers/platform/goldfish (from drivers/misc).
> 
>  drivers/platform/goldfish/Kconfig             |   9 +
>  drivers/platform/goldfish/Makefile            |   1 +
>  .../goldfish/goldfish_address_space.c         | 666 ++++++++++++++++++
>  .../linux/goldfish/goldfish_address_space.h   |  27 +
>  4 files changed, 703 insertions(+)
>  create mode 100644 drivers/platform/goldfish/goldfish_address_space.c
>  create mode 100644 include/uapi/linux/goldfish/goldfish_address_space.h
> 
> diff --git a/drivers/platform/goldfish/Kconfig b/drivers/platform/goldfish/Kconfig
> index 74fdfa68d1f2..60ecec4a3c59 100644
> --- a/drivers/platform/goldfish/Kconfig
> +++ b/drivers/platform/goldfish/Kconfig
> @@ -16,4 +16,13 @@ config GOLDFISH_PIPE
>  	  This is a virtual device to drive the QEMU pipe interface used by
>  	  the Goldfish Android Virtual Device.
>  
> +config GOLDFISH_ADDRESS_SPACE
> +	tristate "A Goldfish driver that talks to the memory sharing device in QEMU"
> +	depends on PCI
> +	depends on GOLDFISH
> +	help
> +	  A Goldfish driver that allocates address space ranges in the guest to
> +	  populate them later in the host. This allows sharing host's memory
> +	  with the guest.

How does QEMU do this today?  There isn't a virtio or some other virtual
memory device that allows memory regions to be shared?  I can't believe
that there isn't one yet.  If not, then this should be some kind of
"generic" QEMU memory device, not a "goldfish" specific one, right?

Please work with the QEMU developers on this, I need their ack before I
can take something like this.

thanks,

greg k-h