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xen: mask _PAGE_PCD from ptes 

_PAGE_PCD maps a page with caching disabled, which is typically used for
mapping harware registers.  Xen never allows it to be set on a mapping, and
unprivileged guests never need it since they can't see the real underlying
hardware.  However, some uncached mappings are made early when probing the
(non-existent) APIC, and its OK to mask off the PCD flag in these cases.

This became necessary because Xen started checking for this bit, rather
than silently masking it off.

Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Jeremy Fitzhardinge 2007-11-28 16:21:20 -08:00 committed by Linus Torvalds
parent c06869d660
commit 2c80b01bea
1 changed files with 4 additions and 0 deletions
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4
arch/x86/xen/mmu.c
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@ -244,6 +244,8 @@ pte_t xen_make_pte(unsigned long long pte)
if (pte & 1)
pte = phys_to_machine(XPADDR(pte)).maddr;
pte &= ~_PAGE_PCD;
return (pte_t){ pte, pte >> 32 };
}
@ -291,6 +293,8 @@ pte_t xen_make_pte(unsigned long pte)
if (pte & _PAGE_PRESENT)
pte = phys_to_machine(XPADDR(pte)).maddr;
pte &= ~_PAGE_PCD;
return (pte_t){ pte };
}