[Intel-gfx] [PATCH v2 1/2] drm/i915/gem: only allow WC for lmem

[Thomas Hellström]

On 6/25/21 2:27 PM, Matthew Auld wrote:
> This is already the case for our kernel internal mappings, and since we
> now only support a single mode this should always be WC if the object
> can be placed in lmem.
>
> v2: rebase and also update set_domain
>
> Signed-off-by: Matthew Auld <matthew.auld at intel.com>
> Cc: Thomas Hellström <thomas.hellstrom at linux.intel.com>
> Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
> Cc: Daniel Vetter <daniel.vetter at ffwll.ch>

A couple of questions:

1) Since this now becomes uapi, are we completely sure that we are not 
going to want to map these bos cached when they are evicted or migrated. 
If we think we are going to want to do that, we should probably just 
silently accept any mapping mode user-space wants and then have the 
kernel override user-space's wishes.

Ping Daniel about this as well.

2) How are we going to handle kernel maps to make sure we don't use a 
different kernel map caching mode to these objects. Will that be a later 
series? Seems like we at least need to modify "i915_coherent_map_type"

Apart from this, code looks good to me.

/Thomas