From: kettenis <kettenis@openbsd.org>
Date: Wed, 15 Aug 2018 20:18:31 +0000 (+0000)
Subject: Use atomic instructions to keep track of what ASIDs are in use.  This makes
X-Git-Url: http://artulab.com/gitweb/?a=commitdiff_plain;h=a31a4de8d8b0e5308bfd84ed442754824029c8b1;p=openbsd

Use atomic instructions to keep track of what ASIDs are in use.  This makes
pmap_free_asid() and therefore pmap_destroy() mpsafe which is important since
we might end up calling that function without holding the kernel lock
as a result of releasing a reference in pmap_page_protect(9).

ok visa@
---

diff --git a/sys/arch/arm64/arm64/pmap.c b/sys/arch/arm64/arm64/pmap.c
index 4641e0f0305..af2294bead1 100644
--- a/sys/arch/arm64/arm64/pmap.c
+++ b/sys/arch/arm64/arm64/pmap.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: pmap.c,v 1.54 2018/06/01 23:10:59 kettenis Exp $ */
+/* $OpenBSD: pmap.c,v 1.55 2018/08/15 20:18:31 kettenis Exp $ */
 /*
  * Copyright (c) 2008-2009,2014-2016 Dale Rahn <drahn@dalerahn.com>
  *
@@ -2169,7 +2169,7 @@ pmap_map_early(paddr_t spa, psize_t len)
  */
 
 #define NUM_ASID (1 << 16)
-uint64_t pmap_asid[NUM_ASID / 64];
+uint32_t pmap_asid[NUM_ASID / 32];
 
 void
 pmap_allocate_asid(pmap_t pm)
@@ -2178,10 +2178,10 @@ pmap_allocate_asid(pmap_t pm)
 
 	do {
 		asid = arc4random() & (NUM_ASID - 2);
-		bit = (asid & (64 - 1));
-	} while (asid == 0 || (pmap_asid[asid / 64] & (3ULL << bit)));
+		bit = (asid & (32 - 1));
+	} while (asid == 0 || (pmap_asid[asid / 32] & (3U << bit)));
 
-	pmap_asid[asid / 64] |= (3ULL << bit);
+	atomic_setbits_int(&pmap_asid[asid / 32], 3U << bit);
 	pm->pm_asid = asid;
 }
 
@@ -2194,8 +2194,8 @@ pmap_free_asid(pmap_t pm)
 	cpu_tlb_flush_asid_all((uint64_t)pm->pm_asid << 48);
 	cpu_tlb_flush_asid_all((uint64_t)(pm->pm_asid | ASID_USER) << 48);
 
-	bit = (pm->pm_asid & (64 - 1));
-	pmap_asid[pm->pm_asid / 64] &= ~(3ULL << bit);
+	bit = (pm->pm_asid & (32 - 1));
+	atomic_clearbits_int(&pmap_asid[pm->pm_asid / 32], 3U << bit);
 }
 
 void