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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.)


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