[PATCH 2/5] xen/x86-64: clean up warnings about IST-using traps

[Jeremy Fitzhardinge <jeremy@goop.org>]

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.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
---
 arch/x86/xen/enlighten.c |   22 ++++++++++++++++++++--
 1 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index cb49f57..88f3aa4 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -439,12 +439,30 @@ 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
-		WARN_ON(val->ist != 0);
+	else if (addr == (unsigned long)double_fault ||
+		 addr == (unsigned long)stack_segment) {
+		/* 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;
 
-- 
1.6.0.6