From: kettenis <kettenis@openbsd.org>
Date: Sun, 16 May 2021 17:41:30 +0000 (+0000)
Subject: Drop PTE check in pmap_fault_fixup().  Since pmap_enter() doesn't
X-Git-Url: http://artulab.com/gitweb/?a=commitdiff_plain;h=beaec7f140cb4d674f26f1bdb850a4abe4a32b7c;p=openbsd

Drop PTE check in pmap_fault_fixup().  Since pmap_enter() doesn't
add PTE's for pages that haven't been accessed yet, the check would
skip the fixup on such pages and force us to go through uvm_fault()
just for the sake of MOD/REF bit emulation.  Since we already check
the PTE descriptor, dropping the check should be safe.  Doing so
gives us a nice 10% performance gain when building a kernel.

ok patrick@, drahn@
---

diff --git a/sys/arch/arm64/arm64/pmap.c b/sys/arch/arm64/arm64/pmap.c
index 50dfaf77e67..4fad269976c 100644
--- a/sys/arch/arm64/arm64/pmap.c
+++ b/sys/arch/arm64/arm64/pmap.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: pmap.c,v 1.77 2021/05/16 15:10:19 deraadt Exp $ */
+/* $OpenBSD: pmap.c,v 1.78 2021/05/16 17:41:30 kettenis Exp $ */
 /*
  * Copyright (c) 2008-2009,2014-2016 Dale Rahn <drahn@dalerahn.com>
  *
@@ -1859,13 +1859,6 @@ pmap_fault_fixup(pmap_t pm, vaddr_t va, vm_prot_t ftype)
 	if (pg == NULL)
 		goto done;
 
-	/*
-	 * Check based on fault type for mod/ref emulation.
-	 * if L3 entry is zero, it is not a possible fixup
-	 */
-	if (*pl3 == 0)
-		goto done;
-
 	/*
 	 * Check the fault types to find out if we were doing
 	 * any mod/ref emulation and fixup the PTE if we were.