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SubjectRe: [GIT PULL] xen /proc/mtrr implementation
Andi Kleen wrote:
>>> Is this new interface only defined for swiotlb or MMIO mappings?
>>> If yes did you check the drivers only actually set it on
>>> swiotlb or MMIO (that seems dubious to me)?
>> Really? Do we ever set unusual memory types on normal system memory?
>
> There were drivers at some point that set WC MTRRs on their
> transfer rings, not mmio.
>
> Maybe these all switched to PAT now, maybe not

Most of those that I've heard of use WB memory and CLFLUSH.

The ones I know of which marked descriptor rings WB were ones which had
descriptor rings in MMIO space (which makes sense: MMIO reads are fully
synchronizing, but writes can be posted and write combined.)

-hpa



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