powerpc: Disable interrupts in 64-bit kernel FP and vector faults

If we get a floating point, altivec or vsx unavaible interrupt in
kernel, we trigger a kernel error. There is no point preserving
the interrupt state, in fact, that can even make debugging harder
as the processor state might change (we may even preempt) between
taking the exception and landing in a debugger.

So just make those 3 disable interrupts unconditionally.
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>
---

v2: On BookE only disable when hitting the kernel unavailable
    path, otherwise it will fail to restore softe as
    fast_exception_return doesn't do it.

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

@@ -354,9 +354,9 @@ interrupt_end_book3e:
 	/* we can probably do a shorter exception entry for that one... */
 	EXCEPTION_COMMON(0x800, PACA_EXGEN, INTS_KEEP)
 	bne	1f			/* if from user, just load it up */
+	INTS_DISABLE_ALL
 	bl	.save_nvgprs
 	addi	r3,r1,STACK_FRAME_OVERHEAD
-	INTS_RESTORE_HARD
 	bl	.kernel_fp_unavailable_exception
 	BUG_OPCODE
 1:	ld	r12,_MSR(r1)
@@ -391,10 +391,9 @@ interrupt_end_book3e:
 /* Auxiliary Processor Unavailable Interrupt */
 	START_EXCEPTION(ap_unavailable);
 	NORMAL_EXCEPTION_PROLOG(0xf20, PROLOG_ADDITION_NONE)
-	EXCEPTION_COMMON(0xf20, PACA_EXGEN, INTS_KEEP)
-	addi	r3,r1,STACK_FRAME_OVERHEAD
+	EXCEPTION_COMMON(0xf20, PACA_EXGEN, INTS_DISABLE_ALL)
 	bl	.save_nvgprs
-	INTS_RESTORE_HARD
+	addi	r3,r1,STACK_FRAME_OVERHEAD
 	bl	.unknown_exception
 	b	.ret_from_except
 

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

@@ -762,8 +762,8 @@ fp_unavailable_common:
 	EXCEPTION_PROLOG_COMMON(0x800, PACA_EXGEN)
 	bne	1f			/* if from user, just load it up */
 	bl	.save_nvgprs
+	DISABLE_INTS
 	addi	r3,r1,STACK_FRAME_OVERHEAD
-	ENABLE_INTS
 	bl	.kernel_fp_unavailable_exception
 	BUG_OPCODE
 1:	bl	.load_up_fpu
@@ -782,8 +782,8 @@ BEGIN_FTR_SECTION
 END_FTR_SECTION_IFSET(CPU_FTR_ALTIVEC)
 #endif
 	bl	.save_nvgprs
+	DISABLE_INTS
 	addi	r3,r1,STACK_FRAME_OVERHEAD
-	ENABLE_INTS
 	bl	.altivec_unavailable_exception
 	b	.ret_from_except
 
@@ -798,8 +798,8 @@ BEGIN_FTR_SECTION
 END_FTR_SECTION_IFSET(CPU_FTR_VSX)
 #endif
 	bl	.save_nvgprs
+	DISABLE_INTS
 	addi	r3,r1,STACK_FRAME_OVERHEAD
-	ENABLE_INTS
 	bl	.vsx_unavailable_exception
 	b	.ret_from_except
 

arch/powerpc/kernel/traps.c

@@ -247,6 +247,9 @@ void _exception(int signr, struct pt_regs *regs, int code, unsigned long addr)
 				   addr, regs->nip, regs->link, code);
 	}
 
+	if (!arch_irq_disabled_regs(regs))
+		local_irq_enable();
+
 	memset(&info, 0, sizeof(info));
 	info.si_signo = signr;
 	info.si_code = code;