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    SubjectRe: Mapping large framebuffers into kernel space
    --- Alan Cox <alan@lxorguk.ukuu.org.uk> wrote:
    >
    > The kernel has 4Gb of virtual address space. Because of the way x86
    > works it really wants to keep the user map, the view of main memory and
    > io mappings visible at once. For larger objects you have to use kmap and
    > map them through a window (anyone remember they joys of EMS). On
    > 64bit this of course all goes away
    >

    On my system I have 1GB physical and 1GB swap. So there should always be some
    open address space in the 1-4GB kernel address space. Would it be better to map
    the framebuffer to 1-4GB when HIGHMEM is configured? Is there an ioremap() that
    will map to high memory? Seems that this would be better than reserving 256MB
    in the 0-1GB range and forcing 256MB of physical RAM into highmem.

    The kernel DRM drivers map framebuffers up to 256MB in size into user space.
    Could this be mapped as a single 256MB page instead of 64K 4KB ones?

    We're working on the radeon drivers right now so I can try a few things out.

    =====
    Jon Smirl
    jonsmirl@yahoo.com

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