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    SubjectRe: [PATCH] phys_efi_set_virtual_address_map needs va, no pa.
    On 06/21/2012 09:52 AM, Robin Holt wrote:
    >
    > I am completely lost as to what should be done. How do we know
    > which identity maps need to be created? Do we just add them as we are
    > scanning the e820/EFI memory maps and include the reserved, etc ranges?
    > Do we look at the table handed to us by EFI at the beginning of boot and
    > use that as the basis? Or do we simply wait until the kernel's memory
    > initialization is complete and cover all of physical memory from zero
    > up to the highest physical address?
    >

    Robin, we already create the 1:1 maps. Right now there is some
    weirdness with some of the issues that you mention, but that is
    orthogonal to this.

    The 1:1 map created for the kernel is created at a specific offset,
    __PAGE_OFFSET, and is propagated into every vm context created by the
    kernel. There are two problems:

    1. The "initial" (32 bit) or "trampoline" (64 bit) maps aren't on the
    list of vm contexts created by the kernel (pgd_list), so they never get
    updated after a particular point in the boot.

    2. The initial/trampoline maps need these mappings not just at address
    __PAGE_OFFSET, but also at address zero (identity mapping), which means
    that just adding it to the pgd_list is insufficient.

    Note that i386-PAE is unaffected, simply because the contents of the top
    (3rd) level is always fixed.

    -hpa



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