xen: add support for PAT
Convert Linux PAT entries into Xen ones when constructing ptes. Linux
doesn't use _PAGE_PAT for ptes, so the only difference in the first 4
entries is that Linux uses _PAGE_PWT for WC, whereas Xen (and default)
use it for WT.
xen_pte_val does the inverse conversion.
We hard-code assumptions about Linux's current PAT layout, but a
warning on the wrmsr to MSR_IA32_CR_PAT should point out any problems.
If necessary we could go to a more general table-based conversion between
Linux and Xen PAT entries.
hugetlbfs poses a problem at the moment, the x86 architecture uses the
same flag for _PAGE_PAT and _PAGE_PSE, which changes meaning depending
on which pagetable level we're using. At the moment this should be OK
so long as nobody tries to do a pte_val on a hugetlbfs pte.
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index d887301..b860e57 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -829,6 +829,11 @@
Xen console noise. */
break;
+ case MSR_IA32_CR_PAT:
+ if (smp_processor_id() == 0)
+ xen_set_pat(((u64)high << 32) | low);
+ break;
+
default:
ret = native_write_msr_safe(msr, low, high);
}