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    SubjectRe: [PATCH] xen: do not set NX bit when making initial pagetables readonly
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    I meant to CC lkml and stable@ (some of the original reports are against
    2.6.27) and fat-fingered the to: line.

    A few previous threads on the subject:
    http://lists.xensource.com/archives/html/xen-devel/2009-01/msg00176.html
    http://www.redhat.com/archives/fedora-xen/2009-January/msg00022.html
    http://www.redhat.com/archives/fedora-virt/2009-January/msg00013.html

    Ian.

    On Fri, 2009-01-30 at 18:19 +0000, Ian Campbell wrote:
    > __supported_pte_mask has not been correctly configured at this point
    > and Xen prevents us from using the NX bit if the hardware does not
    > support it. Some BIOSes seem to offer the option to disable NX.
    >
    > Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
    > Cc: Mark McLoughlin <markmc@redhat.com>
    > Cc: Jon Swanson <jswanson@valuecommerce.co.jp>
    > Cc: fedora-virt@redhat.com
    > Cc: Jeremy Fitzhardinge <jeremy@goop.org>
    > Cc: Ingo Molnar <mingo@elte.hu>
    > ---
    > arch/x86/xen/enlighten.c | 24 +++++++++++++-----------
    > 1 files changed, 13 insertions(+), 11 deletions(-)
    >
    > diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
    > index bea2152..e705bdf 100644
    > --- a/arch/x86/xen/enlighten.c
    > +++ b/arch/x86/xen/enlighten.c
    > @@ -53,6 +53,8 @@
    > #include "mmu.h"
    > #include "multicalls.h"
    >
    > +#define _KERNPG_TABLE_RO __pgprot(_KERNPG_TABLE & ~_PAGE_RW)
    > +
    > EXPORT_SYMBOL_GPL(hypercall_page);
    >
    > DEFINE_PER_CPU(struct vcpu_info *, xen_vcpu);
    > @@ -1487,9 +1489,9 @@ static __init void xen_map_identity_early(pmd_t *pmd, unsigned long max_pfn)
    > }
    >
    > for (pteidx = 0; pteidx < ident_pte; pteidx += PTRS_PER_PTE)
    > - set_page_prot(&level1_ident_pgt[pteidx], PAGE_KERNEL_RO);
    > + set_page_prot(&level1_ident_pgt[pteidx], _KERNPG_TABLE_RO);
    >
    > - set_page_prot(pmd, PAGE_KERNEL_RO);
    > + set_page_prot(pmd, _KERNPG_TABLE_RO);
    > }
    >
    > #ifdef CONFIG_X86_64
    > @@ -1543,12 +1545,12 @@ static __init pgd_t *xen_setup_kernel_pagetable(pgd_t *pgd,
    > xen_map_identity_early(level2_ident_pgt, max_pfn);
    >
    > /* Make pagetable pieces RO */
    > - set_page_prot(init_level4_pgt, PAGE_KERNEL_RO);
    > - set_page_prot(level3_ident_pgt, PAGE_KERNEL_RO);
    > - set_page_prot(level3_kernel_pgt, PAGE_KERNEL_RO);
    > - set_page_prot(level3_user_vsyscall, PAGE_KERNEL_RO);
    > - set_page_prot(level2_kernel_pgt, PAGE_KERNEL_RO);
    > - set_page_prot(level2_fixmap_pgt, PAGE_KERNEL_RO);
    > + set_page_prot(init_level4_pgt, _KERNPG_TABLE_RO);
    > + set_page_prot(level3_ident_pgt, _KERNPG_TABLE_RO);
    > + set_page_prot(level3_kernel_pgt, _KERNPG_TABLE_RO);
    > + set_page_prot(level3_user_vsyscall, _KERNPG_TABLE_RO);
    > + set_page_prot(level2_kernel_pgt, _KERNPG_TABLE_RO);
    > + set_page_prot(level2_fixmap_pgt, _KERNPG_TABLE_RO);
    >
    > /* Pin down new L4 */
    > pin_pagetable_pfn(MMUEXT_PIN_L4_TABLE,
    > @@ -1597,9 +1599,9 @@ static __init pgd_t *xen_setup_kernel_pagetable(pgd_t *pgd,
    > set_pgd(&swapper_pg_dir[KERNEL_PGD_BOUNDARY],
    > __pgd(__pa(level2_kernel_pgt) | _PAGE_PRESENT));
    >
    > - set_page_prot(level2_kernel_pgt, PAGE_KERNEL_RO);
    > - set_page_prot(swapper_pg_dir, PAGE_KERNEL_RO);
    > - set_page_prot(empty_zero_page, PAGE_KERNEL_RO);
    > + set_page_prot(level2_kernel_pgt, _KERNPG_TABLE_RO);
    > + set_page_prot(swapper_pg_dir, _KERNPG_TABLE_RO);
    > + set_page_prot(empty_zero_page, _KERNPG_TABLE_RO);
    >
    > pin_pagetable_pfn(MMUEXT_UNPIN_TABLE, PFN_DOWN(__pa(pgd)));
    >



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