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    Subject[028/136] xen: check EFER for NX before setting up GDT mapping
    2.6.31-stable review patch.  If anyone has any objections, please let us know.

    ------------------
    From: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>

    commit b75fe4e5b869f8dbebd36df64a7fcda0c5b318ed upstream.

    x86-64 assumes NX is available by default, so we need to
    explicitly check for it before using NX. Some first-generation
    Intel x86-64 processors didn't support NX, and even recent systems
    allow it to be disabled in BIOS.

    [ Impact: prevent Xen crash on NX-less 64-bit machines ]

    Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

    ---
    arch/x86/mm/Makefile | 1 +
    arch/x86/xen/enlighten.c | 10 +++++-----
    2 files changed, 6 insertions(+), 5 deletions(-)

    --- a/arch/x86/mm/Makefile
    +++ b/arch/x86/mm/Makefile
    @@ -4,6 +4,7 @@ obj-y := init.o init_$(BITS).o fault.o
    # Make sure __phys_addr has no stackprotector
    nostackp := $(call cc-option, -fno-stack-protector)
    CFLAGS_ioremap.o := $(nostackp)
    +CFLAGS_init.o := $(nostackp)

    obj-$(CONFIG_SMP) += tlb.o

    --- a/arch/x86/xen/enlighten.c
    +++ b/arch/x86/xen/enlighten.c
    @@ -1083,6 +1083,11 @@ asmlinkage void __init xen_start_kernel(

    __supported_pte_mask |= _PAGE_IOMAP;

    +#ifdef CONFIG_X86_64
    + /* Work out if we support NX */
    + check_efer();
    +#endif
    +
    xen_setup_features();

    /* Get mfn list */
    @@ -1123,11 +1128,6 @@ asmlinkage void __init xen_start_kernel(

    pgd = (pgd_t *)xen_start_info->pt_base;

    -#ifdef CONFIG_X86_64
    - /* Work out if we support NX */
    - check_efer();
    -#endif
    -
    /* Don't do the full vcpu_info placement stuff until we have a
    possible map and a non-dummy shared_info. */
    per_cpu(xen_vcpu, 0) = &HYPERVISOR_shared_info->vcpu_info[0];



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