[Xen-devel] [PATCH for-4.11 v2 2/3] x86: guard against #NM

["Jan Beulich" <JBeulich@xxxxxxxx>]

Just in case we still don't get CR0.TS handling right, prevent a host
crash by honoring exception fixups in do_device_not_available(). This
would in particular cover emulator stubs raising #NM.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
---
v2: Add ASSERT_UNREACHABLE().

--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -1749,7 +1749,21 @@ void do_device_not_available(struct cpu_
 {
     struct vcpu *curr = current;
 
-    BUG_ON(!guest_mode(regs));
+    if ( !guest_mode(regs) )
+    {
+        unsigned long fixup = search_exception_table(regs);
+
+        dprintk(XENLOG_ERR, "#NM: %p [%ps] -> %p\n",
+                _p(regs->rip), _p(regs->rip), _p(fixup));
+        /*
+         * We mustn't come here, but for release builds have the recovery
+         * logic in place nevertheless.
+         */
+        ASSERT_UNREACHABLE();
+        BUG_ON(!fixup);
+        regs->rip = fixup;
+        return;
+    }
 
     vcpu_restore_fpu_lazy(curr);
 





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