[Xen-devel] [PATCH 03/18] xen: create dummy ioapic mapping

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

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@xxxxxxxxxx>
---
 arch/x86/xen/mmu.c |   10 ++++++++++
 1 files changed, 10 insertions(+), 0 deletions(-)

diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 55da7f9..b105b73 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -1907,6 +1907,16 @@ static void xen_set_fixmap(unsigned idx, unsigned long 
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
+
        case FIX_PARAVIRT_BOOTMAP:
                /* This is an MFN, but it isn't an IO mapping from the
                   IO domain */
-- 
1.6.0.6


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