When setting up the initial pagetable, which includes mappings of all low physical memory, ignore a mapping which tries to set the RW bit on an RO pte. An RO pte indicates a page which is part of the current pagetable, and so it cannot be allowed to become RW. Once xen_pagetable_setup_done is called, set_pte reverts to its normal behaviour. Signed-off-by: Jeremy Fitzhardinge Acked-by: Chris Wright Cc: ebiederm@xmission.com (Eric W. Biederman) --- arch/i386/xen/enlighten.c | 27 +++++++++++++++++++++++++-- 1 file changed, 25 insertions(+), 2 deletions(-) =================================================================== --- a/arch/i386/xen/enlighten.c +++ b/arch/i386/xen/enlighten.c @@ -501,7 +501,7 @@ static void xen_write_cr3(unsigned long /* Early in boot, while setting up the initial pagetable, assume everything is pinned. */ -static void xen_alloc_pt_init(struct mm_struct *mm, u32 pfn) +static __init void xen_alloc_pt_init(struct mm_struct *mm, u32 pfn) { BUG_ON(mem_map); /* should only be used early */ make_lowmem_page_readonly(__va(PFN_PHYS(pfn))); @@ -553,9 +553,31 @@ static void *xen_kmap_atomic_pte(struct } #endif +static __init pte_t mask_rw_pte(pte_t *ptep, pte_t pte) +{ + /* If there's an existing pte, then don't allow _PAGE_RW to be set */ + if (pte_val_ma(*ptep) & _PAGE_PRESENT) + pte = __pte_ma(((pte_val_ma(*ptep) & _PAGE_RW) | ~_PAGE_RW) & + pte_val_ma(pte)); + + return pte; +} + +/* Init-time set_pte while constructing initial pagetables, which + doesn't allow RO pagetable pages to be remapped RW */ +static __init void xen_set_pte_init(pte_t *ptep, pte_t pte) +{ + pte = mask_rw_pte(ptep, pte); + + xen_set_pte(ptep, pte); +} + static __init void xen_pagetable_setup_start(pgd_t *base) { pgd_t *xen_pgd = (pgd_t *)xen_start_info->pt_base; + + /* special set_pte for pagetable initialization */ + paravirt_ops.set_pte = xen_set_pte_init; init_mm.pgd = base; /* @@ -603,6 +625,7 @@ static __init void xen_pagetable_setup_d /* This will work as long as patching hasn't happened yet (which it hasn't) */ paravirt_ops.alloc_pt = xen_alloc_pt; + paravirt_ops.set_pte = xen_set_pte; if (!xen_feature(XENFEAT_auto_translated_physmap)) { /* @@ -741,7 +764,7 @@ static const struct paravirt_ops xen_par .kmap_atomic_pte = xen_kmap_atomic_pte, #endif - .set_pte = xen_set_pte, + .set_pte = NULL, /* see xen_pagetable_setup_* */ .set_pte_at = xen_set_pte_at, .set_pmd = xen_set_pmd, -- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/