Re: [PATCH] drm/ttm: provide default page protection for UML

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Am 02.09.21 um 09:43 schrieb Johannes Berg:
On Thu, 2021-09-02 at 07:19 +0100, Anton Ivanov wrote:
I have a question though - why all of DRM is not !UML in config. Not
like we can use them.
I have no idea about that.
Hopefully one of the (other) UML maintainers can answer you.
Touche.

We will discuss that and possibly push a patch to !UML that part of the
tree. IMHO it is not applicable.
As I just said on the other patch, all of this is fallout from my commit
68f5d3f3b654 ("um: add PCI over virtio emulation driver") which is the
first time that you could have PCI on UML.

Without having checked, in this particular case it's probably something
like

	depends on PCI && X86_64

as we've seen in other drivers (idxd, ioat).

The biggest problem is probably that UML internally uses X86_64
(arch/x86/um/Kconfig), which is ... unexpected ... since CONFIG_X86_64
is typically considered the ARCH, and now the ARCH is actually um.

Yeah, as TTM maintainer I was about to NAK that approach here.

Basically you are claiming to be X86_64, but then you don't use the X86_64 architecture and are surprised that it things break somewhere else.

This is not something you can blame on subsystems or even drivers, but rather just a broken architectural design and so needs to be fixed there.

Regards,
Christian.


I think we can just fix that and get rid of this entire class of
problems? Something like

https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fp.sipsolutions.net%2Ffbac19d86637e286.txt&data=04%7C01%7Cchristian.koenig%40amd.com%7Cd773b1e8b66643874d1308d96de56a86%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637661654674393046%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=xBT%2Fj%2FbEgltQfvE%2B7%2FGRV7IctGn3sDvy8ycmBvTTSXU%3D&reserved=0

johannes






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