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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>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
This commit is contained in:
Stefano Stabellini 2011-04-19 14:47:31 +01:00 committed by Konrad Rzeszutek Wilk
parent 24bdb0b62c
commit ee176455e2
1 changed files with 9 additions and 4 deletions
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13
arch/x86/xen/mmu.c
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@ -1473,16 +1473,20 @@ static void xen_pgd_free(struct mm_struct *mm, pgd_t *pgd)
#endif #endif
} }
#ifdef CONFIG_X86_32
static __init pte_t mask_rw_pte(pte_t *ptep, pte_t pte) 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 there's an existing pte, then don't allow _PAGE_RW to be set */
if (pte_val_ma(*ptep) & _PAGE_PRESENT) if (pte_val_ma(*ptep) & _PAGE_PRESENT)
pte = __pte_ma(((pte_val_ma(*ptep) & _PAGE_RW) | ~_PAGE_RW) & pte = __pte_ma(((pte_val_ma(*ptep) & _PAGE_RW) | ~_PAGE_RW) &
pte_val_ma(pte)); 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 * If the new pfn is within the range of the newly allocated
@ -1497,6 +1501,7 @@ static __init pte_t mask_rw_pte(pte_t *ptep, pte_t pte)
return pte; return pte;
} }
#endif /* CONFIG_X86_64 */
/* Init-time set_pte while constructing initial pagetables, which /* Init-time set_pte while constructing initial pagetables, which
doesn't allow RO pagetable pages to be remapped RW */ doesn't allow RO pagetable pages to be remapped RW */