Messages in this thread Patch in this message |  | | | From | Jeremy Fitzhardinge <> | | Subject | [PATCH] xen: clear reserved bits in l3 entries given in the initial pagetables | | Date | Fri, 27 Feb 2009 17:59:18 -0800 |
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From: Ian Campbell <ian.campbell@citrix.com>
In native PAE, the only flag that may be legitimately set in an L3 entry is Present. When Xen grafts the top-level PAE L3 pagetable entries into the L4 pagetable, it must also set the other permissions flags so that the mapped pages are actually accessible.
However, due to a bug in the hypervisor, it validates update to the L3 entries as formal PAE entries, so it will refuse to validate these entries with the extra bits requires for 4-level pagetables.
This patch simply masks the entries back to the bare PAE level, leaving Xen to add whatever bits it feels are necessary.
Signed-off-by: Ian Campbell <ian.campbell@citrix.com> Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com> --- arch/x86/xen/mmu.c | 15 +++++++++++++++ 1 files changed, 15 insertions(+), 0 deletions(-) diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c index 367a7d2..5f034a1 100644 --- a/arch/x86/xen/mmu.c +++ b/arch/x86/xen/mmu.c @@ -1778,6 +1778,7 @@ __init pgd_t *xen_setup_kernel_pagetable(pgd_t *pgd, unsigned long max_pfn) { pmd_t *kernel_pmd; + int i; init_pg_tables_start = __pa(pgd); init_pg_tables_end = __pa(pgd) + xen_start_info->nr_pt_frames*PAGE_SIZE; @@ -1789,6 +1790,20 @@ __init pgd_t *xen_setup_kernel_pagetable(pgd_t *pgd, xen_map_identity_early(level2_kernel_pgt, max_pfn); memcpy(swapper_pg_dir, pgd, sizeof(pgd_t) * PTRS_PER_PGD); + + /* + * When running a 32 bit domain 0 on a 64 bit hypervisor a + * pinned L3 (such as the initial pgd here) contains bits + * which are reserved in the PAE layout but not in the 64 bit + * layout. Unfortunately some versions of the hypervisor + * (incorrectly) validate compat mode guests against the PAE + * layout and hence will not allow such a pagetable to be + * pinned by the guest. Therefore we mask off only the PFN and + * Present bits of the supplied L3. + */ + for (i = 0; i < PTRS_PER_PGD; i++) + swapper_pg_dir[i].pgd &= (PTE_PFN_MASK | _PAGE_PRESENT); + set_pgd(&swapper_pg_dir[KERNEL_PGD_BOUNDARY], __pgd(__pa(level2_kernel_pgt) | _PAGE_PRESENT)); -- 1.6.0.6
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