On 07/23/2010 05:14 PM, Henrique de Moraes Holschuh wrote: > > Well, as it was raised in this thread, ACPI tables are likely to be near RAM > regions used for IPC with the firmware or SMBIOS, and we have no idea of the > kind of crap that could happen if we enable caching on those areas. > I'm really not sure I buy that argument -- at least not on x86: if that is the case, then when PAT is off (and we fall down to MTRR-only control) then we'd have the same failures. If we mark them cacheable and the MTRRs say uncachable, then we will *still* not cache them (since MTRR UC overrides PAT WB -- in fact "PAT off" really just means ALL the pagetables are marked WB.) In that sense it is probably *safer* to map them WB, since the firmware if it uses page tables at all is extremely likely to have all the cache control bits at zero (meaning WB) -- and if it doesn't use page tables, they are functionally zero by default (MTRR control only.) So I think it'd be safer to map them cacheable -- regardless of if we want to copy them to RAM or not. -hpa -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
