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x86: remove the Xen-specific _PAGE_IOMAP PTE flag

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The _PAGE_IO_MAP PTE flag was only used by Xen PV guests to mark PTEs
that were used to map I/O regions that are 1:1 in the p2m.  This
allowed Xen to obtain the correct PFN when converting the MFNs read
from a PTE back to their PFN.

Xen guests no longer use _PAGE_IOMAP for this. Instead mfn_to_pfn()
returns the correct PFN by using a combination of the m2p and p2m to
determine if an MFN corresponds to a 1:1 mapping in the the p2m.

Remove _PAGE_IOMAP, replacing it with _PAGE_UNUSED2 to allow for
future uses of the PTE flag.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Acked-by: "H. Peter Anvin" <hpa@zytor.com>
This commit is contained in:
David Vrabel
2014-01-07 17:03:06 +00:00
committed by Stefano Stabellini
parent 7f2f882245
commit f955371ca9
5 changed files with 7 additions and 12 deletions
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2
arch/x86/xen/enlighten.c
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@@ -1559,8 +1559,6 @@ asmlinkage __visible void __init xen_start_kernel(void)
#endif
__supported_pte_mask &= ~(_PAGE_PWT | _PAGE_PCD);
__supported_pte_mask |= _PAGE_IOMAP;
/*
* Prevent page tables from being allocated in highmem, even
* if CONFIG_HIGHPTE is enabled.