Messages in this thread | | | Date | Wed, 20 May 2009 16:03:23 -0700 | From | "H. Peter Anvin" <> | Subject | Re: [GIT PULL] xen /proc/mtrr implementation |
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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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