Accessing the Metal graphics API with OSX as VM client

Accessing the Metal graphics API with OSX as VM client

[Trystan Larey-Williams]

Hi all,

I'm trying to get a sense of where QEMU headed in terms of supporting 
Apple's Metal API. Apple will likely be removing OpenGL support entirely 
from OSX, perhaps as early as the next major release of OSX in Sep/Oct. 
Information on support for graphics acceleration on an OSX client using 
Metal instead of OpenGL seems non-existent. From the QEMU documentation 
I gather there are a few ways to 'pass through' a device natively to the 
VM. Would this be the only way to currently access Metal on OSX? Has 
anyone actually tried this?

Thanks,
Trystan

Re: Accessing the Metal graphics API with OSX as VM client

[Peter Maydell]

On Tue, 16 Jun 2020 at 21:26, Trystan Larey-Williams
<trystan@trystan.org> wrote:
> I'm trying to get a sense of where QEMU headed in terms of supporting
> Apple's Metal API. Apple will likely be removing OpenGL support entirely
> from OSX, perhaps as early as the next major release of OSX in Sep/Oct.

QEMU on OSX hosts has somewhere between few and no active developers
(almost everybody in the upstream community is on a Linux host) so
the default answer is that we're not headed anywhere. I think that
this is not going to be a loss of functionality because right now we
don't support GL acceleration on OSX hosts either (because there's
no virglrenderer there).

Gerd might know what would be the best approach to virtio-gpu on
an OSX host if there were developers interested in working on it.

> Information on support for graphics acceleration on an OSX client using

[side note: not sure what you mean by "client": host, or guest ?]

> Metal instead of OpenGL seems non-existent. From the QEMU documentation
> I gather there are a few ways to 'pass through' a device natively to the
> VM. Would this be the only way to currently access Metal on OSX? Has
> anyone actually tried this?

Does PCI passthrough work on OSX hosts? My default assumption would be
"no, it doesn't" -- the way we do passthrough on Linux hosts
depends on Linux-specific APIs (VFIO). If you meant "device
passthrough from a Linux host to an OSX guest" there's no reason
in theory why that shouldn't work, if OSX has drivers for whatever
the passed-through hardware is. Equally, if there were a
hypothetical OSX Metal driver for virtio-gpu you could use that.

thanks
-- PMM

Re: Accessing the Metal graphics API with OSX as VM client

[Gerd Hoffmann]

  Hi,

> the default answer is that we're not headed anywhere. I think that
> this is not going to be a loss of functionality because right now we
> don't support GL acceleration on OSX hosts either (because there's
> no virglrenderer there).

vulkan support for virglrenderer is being worked on.  Its far from being
finished though, and I have no clue whenever that actually buys you
something on macos.  Also the implementation will likely depend on some
linux kernel features (specifically dma-bufs for buffer sharing &
mapping), so even if vulkan is available on macos making virglrenderer
work on macos will require non-trivial porting work.

take care,
  Gerd

Re: Accessing the Metal graphics API with OSX as VM client

[Trystan Larey-Williams]

Thanks for the responses on this! That gives me some context to work 
with. I'll likely give 'pass through' a shot (Linux host, OSX guest). I 
folks are curious, I can report the results back.

Cheers,
Trystan

On 6/16/2020 2:08 PM, Peter Maydell wrote:
> On Tue, 16 Jun 2020 at 21:26, Trystan Larey-Williams
> <trystan@trystan.org> wrote:
>> I'm trying to get a sense of where QEMU headed in terms of supporting
>> Apple's Metal API. Apple will likely be removing OpenGL support entirely
>> from OSX, perhaps as early as the next major release of OSX in Sep/Oct.
> QEMU on OSX hosts has somewhere between few and no active developers
> (almost everybody in the upstream community is on a Linux host) so
> the default answer is that we're not headed anywhere. I think that
> this is not going to be a loss of functionality because right now we
> don't support GL acceleration on OSX hosts either (because there's
> no virglrenderer there).
>
> Gerd might know what would be the best approach to virtio-gpu on
> an OSX host if there were developers interested in working on it.
>
>> Information on support for graphics acceleration on an OSX client using
> [side note: not sure what you mean by "client": host, or guest ?]
>
>> Metal instead of OpenGL seems non-existent. From the QEMU documentation
>> I gather there are a few ways to 'pass through' a device natively to the
>> VM. Would this be the only way to currently access Metal on OSX? Has
>> anyone actually tried this?
> Does PCI passthrough work on OSX hosts? My default assumption would be
> "no, it doesn't" -- the way we do passthrough on Linux hosts
> depends on Linux-specific APIs (VFIO). If you meant "device
> passthrough from a Linux host to an OSX guest" there's no reason
> in theory why that shouldn't work, if OSX has drivers for whatever
> the passed-through hardware is. Equally, if there were a
> hypothetical OSX Metal driver for virtio-gpu you could use that.
>
> thanks
> -- PMM