[Xen-devel] [PATCH 2/8] xen/x86-64: clean up warnings about IST-using traps

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

From: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>

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@xxxxxxxxxx>
---
 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 16afbc3..cbb31eb 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


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