On 10/08/2014 12:49 PM, Chris Wilson wrote:
>
> Indeed, this appears to be the explanation. (And here I thought PAT
> superseded mtrrs - i915.ko stopped trying to use assign an mtrr for its
> GTT quite a while ago.)
>
> Replacing the stop_machine there with on_each_cpu does the trick:
>
It should, but there seem to be quite a few drivers which still muck
with MTRRs. However, i915 is not one of them, it calls
io_mapping_create_wc() followed by arch_phys_wc_add(), so I'm wondering
what the heck is going on here.
> Naively I would say that we lost the wc on our ioremap.
> /sys/kernel/debug/x86/pat_memtype_list remained the same across repeated
> runs.
Could you tell me what the above looks like?
-hpa
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