diff --git a/sys/arch/acorn32/include/vmparam.h b/sys/arch/acorn32/include/vmparam.h
index 5e21564aa19a..246577c6874c 100644
--- a/sys/arch/acorn32/include/vmparam.h
+++ b/sys/arch/acorn32/include/vmparam.h
@@ -1,4 +1,4 @@
-/*	$NetBSD: vmparam.h,v 1.16 2003/05/21 22:48:21 thorpej Exp $	*/
+/*	$NetBSD: vmparam.h,v 1.17 2003/05/22 05:25:48 thorpej Exp $	*/
 
 /*
  * Copyright (c) 1988 The Regents of the University of California.
@@ -76,12 +76,6 @@
 
 #define USRIOSIZE       300
 
-/* XXX max. amount of KVM to be used by buffers. */
-#ifndef VM_MAX_KERNEL_BUF
-#define VM_MAX_KERNEL_BUF \
-	((KERNEL_VM_SIZE) * 4 / 10)
-#endif
-
 /* virtual sizes (bytes) for various kernel submaps */
 
 #define VM_PHYS_SIZE		(USRIOSIZE*PAGE_SIZE)
diff --git a/sys/arch/arm/include/arm32/vmparam.h b/sys/arch/arm/include/arm32/vmparam.h
index 5269ac8fdf35..9c3daf294922 100644
--- a/sys/arch/arm/include/arm32/vmparam.h
+++ b/sys/arch/arm/include/arm32/vmparam.h
@@ -1,4 +1,4 @@
-/*	$NetBSD: vmparam.h,v 1.18 2003/05/21 18:04:44 thorpej Exp $	*/
+/*	$NetBSD: vmparam.h,v 1.19 2003/05/22 05:25:48 thorpej Exp $	*/
 
 /*
  * Copyright (c) 2001, 2002 Wasabi Systems, Inc.
@@ -92,6 +92,15 @@
 #define	VM_MIN_KERNEL_ADDRESS	((vaddr_t) KERNEL_BASE)
 #define	VM_MAX_KERNEL_ADDRESS	((vaddr_t) 0xffffffff)
 
+/* XXX max. amount of KVM to be used by buffers. */
+#ifndef VM_MAX_KERNEL_BUF
+extern vaddr_t virtual_avail;
+extern vaddr_t virtual_end;
+
+#define	VM_MAX_KERNEL_BUF	\
+	((virtual_end - virtual_avail) * 4 / 10)
+#endif
+
 /*
  * pmap-specific data store in the vm_page structure.
  */
diff --git a/sys/arch/cats/include/vmparam.h b/sys/arch/cats/include/vmparam.h
index e1802bada013..931929c4ac17 100644
--- a/sys/arch/cats/include/vmparam.h
+++ b/sys/arch/cats/include/vmparam.h
@@ -1,4 +1,4 @@
-/*	$NetBSD: vmparam.h,v 1.21 2003/05/21 22:48:21 thorpej Exp $	*/
+/*	$NetBSD: vmparam.h,v 1.22 2003/05/22 05:25:49 thorpej Exp $	*/
 
 /*
  * Copyright (c) 1988 The Regents of the University of California.
@@ -81,12 +81,6 @@
 
 #define USRIOSIZE       300
 
-/* XXX max. amount of KVM to be used by buffers. */
-#ifndef VM_MAX_KERNEL_BUF
-#define VM_MAX_KERNEL_BUF \
-	(((KERNEL_VM_SIZE) * 4) / 10)
-#endif
-
 /* virtual sizes (bytes) for various kernel submaps */
 
 #define VM_PHYS_SIZE		(USRIOSIZE*PAGE_SIZE)
diff --git a/sys/arch/evbarm/include/vmparam.h b/sys/arch/evbarm/include/vmparam.h
index 0eec883b9789..9861ff76ceed 100644
--- a/sys/arch/evbarm/include/vmparam.h
+++ b/sys/arch/evbarm/include/vmparam.h
@@ -1,4 +1,4 @@
-/*	$NetBSD: vmparam.h,v 1.19 2003/05/21 22:48:21 thorpej Exp $	*/
+/*	$NetBSD: vmparam.h,v 1.20 2003/05/22 05:25:49 thorpej Exp $	*/
 
 /*
  * Copyright (c) 1988 The Regents of the University of California.
@@ -76,12 +76,6 @@
 
 #define USRIOSIZE       300
 
-/* XXX max. amount of KVM to be used by buffers. */
-#ifndef VM_MAX_KERNEL_BUF
-#define VM_MAX_KERNEL_BUF \
-	((KERNEL_VM_SIZE) * 4 / 10)
-#endif
-
 /* virtual sizes (bytes) for various kernel submaps */
 
 #define VM_PHYS_SIZE		(USRIOSIZE*PAGE_SIZE)
diff --git a/sys/arch/hpcarm/include/vmparam.h b/sys/arch/hpcarm/include/vmparam.h
index 2fe990d90da7..c5db2283418c 100644
--- a/sys/arch/hpcarm/include/vmparam.h
+++ b/sys/arch/hpcarm/include/vmparam.h
@@ -1,4 +1,4 @@
-/*	$NetBSD: vmparam.h,v 1.23 2003/05/21 22:48:23 thorpej Exp $	*/
+/*	$NetBSD: vmparam.h,v 1.24 2003/05/22 05:25:50 thorpej Exp $	*/
 
 /*
  * Copyright (c) 1988 The Regents of the University of California.
@@ -72,12 +72,6 @@
 
 #define USRIOSIZE       300
 
-/* XXX max. amount of KVM to be used by buffers. */
-#ifndef VM_MAX_KERNEL_BUF
-#define VM_MAX_KERNEL_BUF \
-	((KERNEL_VM_SIZE) * 4 / 10)
-#endif
-
 /* virtual sizes (bytes) for various kernel submaps */
 
 #define VM_PHYS_SIZE		(USRIOSIZE*PAGE_SIZE)
diff --git a/sys/arch/netwinder/include/vmparam.h b/sys/arch/netwinder/include/vmparam.h
index eeea01ecaf5a..c5cea738be09 100644
--- a/sys/arch/netwinder/include/vmparam.h
+++ b/sys/arch/netwinder/include/vmparam.h
@@ -1,4 +1,4 @@
-/*	$NetBSD: vmparam.h,v 1.19 2003/05/21 22:48:23 thorpej Exp $	*/
+/*	$NetBSD: vmparam.h,v 1.20 2003/05/22 05:25:50 thorpej Exp $	*/
 
 /*
  * Copyright (c) 1988 The Regents of the University of California.
@@ -76,12 +76,6 @@
 
 #define USRIOSIZE       300
 
-/* XXX max. amount of KVM to be used by buffers. */
-#ifndef VM_MAX_KERNEL_BUF
-#define VM_MAX_KERNEL_BUF \
-	((KERNEL_VM_SIZE) * 4 / 10)
-#endif
-
 /* virtual sizes (bytes) for various kernel submaps */
 
 #define VM_PHYS_SIZE		(USRIOSIZE*PAGE_SIZE)
diff --git a/sys/arch/shark/include/vmparam.h b/sys/arch/shark/include/vmparam.h
index 9866f324ca1e..4ccfe39eeac1 100644
--- a/sys/arch/shark/include/vmparam.h
+++ b/sys/arch/shark/include/vmparam.h
@@ -1,4 +1,4 @@
-/*	$NetBSD: vmparam.h,v 1.11 2003/05/21 22:48:24 thorpej Exp $	*/
+/*	$NetBSD: vmparam.h,v 1.12 2003/05/22 05:25:51 thorpej Exp $	*/
 
 /*
  * Copyright (c) 1988 The Regents of the University of California.
@@ -67,12 +67,6 @@
 
 #define USRIOSIZE       300
 
-/* XXX max. amount of KVM to be used by buffers. */
-#ifndef VM_MAX_KERNEL_BUF
-#define VM_MAX_KERNEL_BUF \
-	((KERNEL_VM_SIZE) * 4 / 10)
-#endif
-
 /* virtual sizes (bytes) for various kernel submaps */
 
 #define VM_PHYS_SIZE		(USRIOSIZE*PAGE_SIZE)