powerpc/64s/exception: Add the virt variant of the denorm interrupt handler

All other virt handlers have the prolog code in the virt vector rather
than branch to the real vector. Follow this pattern in the denorm virt
handler.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20190802105709.27696-25-npiggin@gmail.com

arch/powerpc/kernel/exceptions-64s.S

@@ -1852,7 +1852,11 @@ EXC_REAL_END(denorm_exception_hv, 0x1500, 0x100)
 
 #ifdef CONFIG_PPC_DENORMALISATION
 EXC_VIRT_BEGIN(denorm_exception, 0x5500, 0x100)
-	b	exc_real_0x1500_denorm_exception_hv
+	INT_HANDLER denorm_exception, 0x1500, 0, 2, 1, EXC_HV, PACA_EXGEN, 1, 0, 0, 0, 0
+	mfspr	r10,SPRN_HSRR1
+	andis.	r10,r10,(HSRR1_DENORM)@h /* denorm? */
+	bne+	denorm_assist
+	INT_VIRT_SAVE_SRR_AND_JUMP denorm_common, EXC_HV
 EXC_VIRT_END(denorm_exception, 0x5500, 0x100)
 #else
 EXC_VIRT_NONE(0x5500, 0x100)