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Commit ee176455 authored by Stefano Stabellini's avatar Stefano Stabellini Committed by Konrad Rzeszutek Wilk
Browse files

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: default avatarStefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
parent 24bdb0b6

arch/x86/xen/mmu.c

+9 −4
Original line number Original line Diff line number Diff line
@@ -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 */