Commit ee176455 authored Apr 19, 2011 by Stefano Stabellini Committed by Konrad Rzeszutek Wilk Apr 20, 2011

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>

parent 24bdb0b6

arch/x86/xen/mmu.c

+9 −4

Original line number	Diff line number	Diff line
		@@ -1473,16 +1473,20 @@ 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
		@@ -1497,6 +1501,7 @@ 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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