>HOWEVER, if you tied the GART mapping to the DRM lock, you might be ok.
>That gives you the required system exclusion, and if you make it an
>explicit "get my GART context" function that is only called under the DRM
>lock _and_ only called when you actually need the AGP access, you also
>avoid the unnecessary context switches.
>
>You might still have some performance issues simply because you would do
>extra work when switching aperture mappings, but hopefully the GART switch
>wouldn't be a common operation.
>
>The flexibility you would get _might_ be worth it.
Well, I would personally vote for the processes _not_ relying on having
the AGP aperture mapped directly, but instead, the various memory pages
making their AGP aperture. Several chipsets (Apple ones for sure, but it
seems others are hitting this too nowadays) don't support AGP aperture
accesses from the CPU.
That way, if you want several AGP contexts, you can have the processes
tapping their AGP buffers without lock, locking would only be required
once it's time to move one of these buffers in/out the physical GART
under the arbitration of the DRM.
Ben.
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