[PATCH] drm/amdgpu: select ARCH_HAS_HMM and ZONE_DEVICE option

[Jerome Glisse]

On Wed, Feb 20, 2019 at 10:39:49PM +0000, Kuehling, Felix wrote:
> On 2019-02-20 5:12 p.m., Jerome Glisse wrote:
> > On Wed, Feb 20, 2019 at 07:18:17PM +0000, Kuehling, Felix wrote:
> >> [+Jerome]
> >>
> >> Why to we need ZONE_DEVICE. I didn't think this was needed for mirroring
> >> CPU page tables to device page tables.
> >>
> >> ARCH_HAS_HMM depends on (X86_64 || PPC64). Do we have some alternative
> >> for ARM support?
> >>
> >> Also, the name ARCH_HAS_HMM looks like it's meant to be selected by the
> >> CPU architecture rather than any driver. Jerome, do you have any advice?
> > This patch is wrong you need to depend on ARCH_HAS_HMM and
> 
> Who selects ARCH_HAS_HMM? Currently I don't see this selected anywhere. 
> So any config option that depends on it will be invisible in menuconfig. 
> Do we need ARCH_HAS_HMM somewhere in the arch/x86/Kconfig and 
> arch/powerpc/Kconfig?
> 
> Also, ARCH_HAS_HMM does not currently support ARM. Does that mean we 
> can't have ARM support in AMDGPU if we start using HMM?

ARCH_HAS_HMM is defined by architecture that support HMM. So par x86
and PPC. It should not be hard to add it to ARM (i can not remember if
ARM has DAX yet or not, if ARM does not have DAX then you need to add
that first).

> 
> Finally, ARCH_HAS_HMM has a bunch of dependencies. If they are not met, 
> I guess it can't be enabled. Should those be "select"s instead?

No they should not be selected, people configuring their system need
to have the freedom of doing so. All those option are selected in all
the big distribution.

> config ARCH_HAS_HMM
>          bool
>          default y
>          depends on (X86_64 || PPC64)
>          depends on ZONE_DEVICE
>          depends on MMU && 64BIT
>          depends on MEMORY_HOTPLUG
>          depends on MEMORY_HOTREMOVE
>          depends on SPARSEMEM_VMEMMAP
> 

Cheers,
Jérôme