xen: create dummy ioapic mapping

Impact: debuggability (make failures obvious)

We don't allow direct access to the IO apic, so make sure that any
request to map it just "maps" non-present pages.  We should see any
attempts at direct access explode nicely.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>

diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 4ceb28581652ef0ab7ff7bcc5426dd914954d100..a5b0d487420c707ccd890ba7ef7507031b528574 100644 (file)
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -1824,6 +1824,16 @@ static void xen_set_fixmap(unsigned idx, phys_addr_t phys, pgprot_t prot)
                pte = pfn_pte(phys, prot);
                break;
 
+#ifdef CONFIG_X86_IO_APIC
+       case FIX_IO_APIC_BASE_0 ... FIX_IO_APIC_BASE_END:
+               /*
+                * We just don't map the IO APIC - all access is via
+                * hypercalls.  Keep the address in the pte for reference.
+                */
+               pte = pfn_pte(phys, PAGE_NONE);
+               break;
+#endif
+
        default:
                pte = mfn_pte(phys, prot);
                break;