Messages in this thread Patch in this message | | | Date | Thu, 15 Nov 2007 13:49:16 -0800 | From | Jeremy Fitzhardinge <> | Subject | [PATCH RESEND] xen: mask _PAGE_PCD from ptes |
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_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> --- arch/x86/xen/mmu.c | 4 ++++ 1 file changed, 4 insertions(+)
=================================================================== --- a/arch/x86/xen/mmu.c +++ b/arch/x86/xen/mmu.c @@ -244,6 +244,8 @@ pte_t xen_make_pte(unsigned long long pt if (pte & 1) pte = phys_to_machine(XPADDR(pte)).maddr; + pte &= ~_PAGE_PCD; + return (pte_t){ pte, pte >> 32 }; } @@ -290,6 +292,8 @@ 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 }; }
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