xen/x86-64: clean up warnings about IST-using traps

Ignore known IST-using traps.  Aside from the debugger traps, they're
low-level faults which Xen will handle for us, so the kernel needn't
worry about them.  Keep warning in case unknown trap starts using IST.

Impact: suppress spurious warnings
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>

1 files changed, 20 insertions, 2 deletions

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 7566e13c0cac..e9df942aa143 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -439,14 +439,32 @@ static int cvt_gate_to_trap(int vector, const gate_desc *val,
 
         addr = gate_offset(*val);
 #ifdef CONFIG_X86_64
+        /*
+         * Look for known traps using IST, and substitute them
+         * appropriately.  The debugger ones are the only ones we care
+         * about.  Xen will handle faults like double_fault and
+         * machine_check, so we should never see them.  Warn if
+         * there's an unexpected IST-using fault handler.
+         */
         if (addr == (unsigned long)debug)
                 addr = (unsigned long)xen_debug;
         else if (addr == (unsigned long)int3)
                 addr = (unsigned long)xen_int3;
         else if (addr == (unsigned long)stack_segment)
                 addr = (unsigned long)xen_stack_segment;
-        else
-                WARN_ON(val->ist != 0);
+        else if (addr == (unsigned long)double_fault ||
+                 addr == (unsigned long)nmi) {
+                /* Don't need to handle these */
+                return 0;
+#ifdef CONFIG_X86_MCE
+        } else if (addr == (unsigned long)machine_check) {
+                return 0;
+#endif
+        } else {
+                /* Some other trap using IST? */
+                if (WARN_ON(val->ist != 0))
+                        return 0;
+        }
 #endif  /* CONFIG_X86_64 */
         info->address = addr;