Stefano Stabellini
2011-Apr-19 13:47 UTC
[Xen-devel] xen: mask_rw_pte: do not apply the early_ioremap checks on x86_32
The two "is_early_ioremap_ptep" checks in mask_rw_pte are only used on
x86_64, in fact early_ioremap is not used at all to setup the initial
pagetable on x86_32.
Moreover on x86_32 the two checks are wrong because the range
pgt_buf_start..pgt_buf_end initially should be mapped RW because
the pages in the range are not pagetable pages yet and haven''t been
cleared yet. Afterwards considering the pgt_buf_start..pgt_buf_end is
part of the initial mapping, xen_alloc_pte is capable of turning
the ptes RO when they become pagetable pages.
Fix the issue and improve the readability of the code providing two
different implementation of mask_rw_pte for x86_32 and x86_64.
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 7ad0292..1e1808d 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -1487,16 +1487,20 @@ static void xen_pgd_free(struct mm_struct *mm, pgd_t
*pgd)
#endif
}
+#ifdef CONFIG_X86_32
static __init pte_t mask_rw_pte(pte_t *ptep, pte_t pte)
{
- unsigned long pfn = pte_pfn(pte);
-
-#ifdef CONFIG_X86_32
/* 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));
-#endif
+
+ return pte;
+}
+#else /* CONFIG_X86_64 */
+static __init pte_t mask_rw_pte(pte_t *ptep, pte_t pte)
+{
+ unsigned long pfn = pte_pfn(pte);
/*
* If the new pfn is within the range of the newly allocated
@@ -1511,6 +1515,7 @@ static __init pte_t mask_rw_pte(pte_t *ptep, pte_t pte)
return pte;
}
+#endif /* CONFIG_X86_64 */
/* Init-time set_pte while constructing initial pagetables, which
doesn''t allow RO pagetable pages to be remapped RW */
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