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    Subject[patch 044/104] xen: do not reserve 2 pages of padding between hypervisor and fixmap.
    2.6.27-stable review patch.  If anyone has any objections, please let us know.

    From: Ian Campbell <>

    commit 5dc64a3442b98eaa0e3730c35fcf00cf962a93e7 upstream.

    When reserving space for the hypervisor the Xen paravirt backend adds
    an extra two pages (this was carried forward from the 2.6.18-xen tree
    which had them "for safety"). Depending on various CONFIG options this
    can cause the boot time fixmaps to span multiple PMDs which is not
    supported and triggers a WARN in early_ioremap_init().

    This was exposed by 2216d199b1430d1c0affb1498a9ebdbd9c0de439 which
    moved the dmi table parsing earlier.
    x86: fix CONFIG_X86_RESERVE_LOW_64K=y

    The bad_bios_dmi_table() quirk never triggered because we do DMI setup
    too late. Move it a bit earlier.

    There is no real reason to reserve these two extra pages and the
    fixmap already incorporates FIX_HOLE which serves the same
    purpose. None of the other callers of reserve_top_address do this.

    Signed-off-by: Ian Campbell <>
    Signed-off-by: Ingo Molnar <>
    Cc: Jeremy Fitzhardinge <>
    Signed-off-by: Greg Kroah-Hartman <>

    arch/x86/xen/enlighten.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    --- a/arch/x86/xen/enlighten.c
    +++ b/arch/x86/xen/enlighten.c
    @@ -1413,7 +1413,7 @@ static void __init xen_reserve_top(void)
    if (HYPERVISOR_xen_version(XENVER_platform_parameters, &pp) == 0)
    top = pp.virt_start;

    - reserve_top_address(-top + 2 * PAGE_SIZE);
    + reserve_top_address(-top);
    #endif /* CONFIG_X86_32 */

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