powerpc/64s: split do_hash_fault

This is required for subsequent interrupt wrapper implementation.
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210130130852.2952424-16-npiggin@gmail.com

arch/powerpc/mm/book3s64/hash_utils.c

@@ -1512,7 +1512,7 @@ int hash_page(unsigned long ea, unsigned long access, unsigned long trap,
 }
 EXPORT_SYMBOL_GPL(hash_page);
 
-long do_hash_fault(struct pt_regs *regs)
+static long __do_hash_fault(struct pt_regs *regs)
 {
 	unsigned long ea = regs->dar;
 	unsigned long dsisr = regs->dsisr;
@@ -1522,27 +1522,6 @@ long do_hash_fault(struct pt_regs *regs)
 	unsigned int region_id;
 	long err;
 
-	if (unlikely(dsisr & (DSISR_BAD_FAULT_64S | DSISR_KEYFAULT)))
-		goto page_fault;
-
-	/*
-	 * If we are in an "NMI" (e.g., an interrupt when soft-disabled), then
-	 * don't call hash_page, just fail the fault. This is required to
-	 * prevent re-entrancy problems in the hash code, namely perf
-	 * interrupts hitting while something holds H_PAGE_BUSY, and taking a
-	 * hash fault. See the comment in hash_preload().
-	 *
-	 * We come here as a result of a DSI at a point where we don't want
-	 * to call hash_page, such as when we are accessing memory (possibly
-	 * user memory) inside a PMU interrupt that occurred while interrupts
-	 * were soft-disabled.  We want to invoke the exception handler for
-	 * the access, or panic if there isn't a handler.
-	 */
-	if (unlikely(in_nmi())) {
-		bad_page_fault(regs, SIGSEGV);
-		return 0;
-	}
-
 	region_id = get_region_id(ea);
 	if ((region_id == VMALLOC_REGION_ID) || (region_id == IO_REGION_ID))
 		mm = &init_mm;
@@ -1581,8 +1560,39 @@ long do_hash_fault(struct pt_regs *regs)
 			bad_page_fault(regs, SIGBUS);
 		}
 		err = 0;
+	}
+
+	return err;
+}
+
+long do_hash_fault(struct pt_regs *regs)
+{
+	unsigned long dsisr = regs->dsisr;
+	long err;
+
+	if (unlikely(dsisr & (DSISR_BAD_FAULT_64S | DSISR_KEYFAULT)))
+		goto page_fault;
+
+	/*
+	 * If we are in an "NMI" (e.g., an interrupt when soft-disabled), then
+	 * don't call hash_page, just fail the fault. This is required to
+	 * prevent re-entrancy problems in the hash code, namely perf
+	 * interrupts hitting while something holds H_PAGE_BUSY, and taking a
+	 * hash fault. See the comment in hash_preload().
+	 *
+	 * We come here as a result of a DSI at a point where we don't want
+	 * to call hash_page, such as when we are accessing memory (possibly
+	 * user memory) inside a PMU interrupt that occurred while interrupts
+	 * were soft-disabled.  We want to invoke the exception handler for
+	 * the access, or panic if there isn't a handler.
+	 */
+	if (unlikely(in_nmi())) {
+		bad_page_fault(regs, SIGSEGV);
+		return 0;
+	}
 
-	} else if (err) {
+	err = __do_hash_fault(regs);
+	if (err) {
 page_fault:
 		err = do_page_fault(regs);
 	}