x86/traps: export the exception_table[] function pointer table to C

and use it in preference to the direct call to do_nmi() in vmx.c

The value 'TRAP_last_reserved' was only used where 'TRAP_nr' would be more
appropriate, so is replaced.

No functional change

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
master commit: d3eb16b8a7
master date: 2015-02-11 17:16:18 +0100

xen/arch/x86/hvm/vmx/vmx.c

@@ -2507,7 +2507,7 @@ void vmx_vmexit_handler(struct cpu_user_regs *regs)
              && ((intr_info & INTR_INFO_INTR_TYPE_MASK) ==
                  (X86_EVENTTYPE_NMI << 8)) )
         {
-            do_nmi(regs);
+            exception_table[TRAP_nmi](regs);
             enable_nmis();
         }
         break;

xen/arch/x86/x86_64/entry.S

@@ -721,6 +721,7 @@ ENTRY(exception_table)
         .quad do_alignment_check
         .quad do_machine_check
         .quad do_simd_coprocessor_error
+        .size exception_table, . - exception_table
 
 ENTRY(hypercall_table)
         .quad do_set_trap_table     /*  0 */

xen/include/asm-x86/processor.h

@@ -112,7 +112,7 @@
 #define TRAP_alignment_check  17
 #define TRAP_machine_check    18
 #define TRAP_simd_error       19
-#define TRAP_last_reserved    31
+#define TRAP_nr               32
 
 /* Set for entry via SYSCALL. Informs return code to use SYSRETQ not IRETQ. */
 /* NB. Same as VGCF_in_syscall. No bits in common with any other TRAP_ defn. */
@@ -522,6 +522,9 @@ extern void mtrr_bp_init(void);
 
 void mcheck_init(struct cpuinfo_x86 *c, bool_t bsp);
 
+/* Dispatch table for exceptions */
+extern void (* const exception_table[TRAP_nr])(struct cpu_user_regs *regs);
+
 #define DECLARE_TRAP_HANDLER(_name)                     \
 void _name(void);                            \
 void do_ ## _name(struct cpu_user_regs *regs)