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    SubjectRe: [RFC][patch 0/2] mm: remove PageReserved
    On Tue, 9 Aug 2005, Benjamin Herrenschmidt wrote:
    >
    > > ioremap is making a similar check to the one remap_pfn_range used
    > > to make; but I see no good reason for it at all. ioremap should be
    > > allowed to map whatever the caller asked, just as memset is allowed
    > > to set whatever the caller asked.
    >
    > This is dodgy actually. memset can't be guaranteed to work on IOs or
    > other non-cacheable memory (including real RAM that has been mapped
    > non-cacheable, typically RAM that has been "set aside" for other uses as
    > described above, wether it's for AGP, or for some weird processor DMA
    > bounce buffers or whatever ..., that is RAM that is out of the normal
    > kernel control).

    That was my point: memset goes ahead without making funny little checks,
    and works or not, so I don't see why ioremap needs to make these funny
    little checks. If the driver doesn't know what it's doing (not impossible,
    I accept), what's the likelihood that PageReserved or not will save it?

    Hugh
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