diff --git a/sys/amd64/amd64/cpu_switch.S b/sys/amd64/amd64/cpu_switch.S
index 571d9c9dbc8b..62a970296c26 100644
--- a/sys/amd64/amd64/cpu_switch.S
+++ b/sys/amd64/amd64/cpu_switch.S
@@ -33,7 +33,7 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- *	$Id: swtch.s,v 1.16 1994/10/25 07:25:56 davidg Exp $
+ *	$Id: swtch.s,v 1.17 1994/10/30 20:09:13 bde Exp $
  */
 
 #include "npx.h"	/* for NNPX */
@@ -250,13 +250,19 @@ _idle:
 	ALIGN_TEXT
 idle_loop:
 	cli
+	movb	$1,_intr_nesting_level		/* charge Intr if we leave */
 	cmpl	$0,_whichrtqs			/* real-time queue */
 	jne	sw1a
 	cmpl	$0,_whichqs			/* normal queue */
 	jne	nortqr
 	cmpl	$0,_whichidqs			/* 'idle' queue */
 	jne	idqr
+	movb	$0,_intr_nesting_level		/* charge Idle for this loop */
 #ifdef APM
+	/*
+	 * XXX it breaks the rules to call a function while interrupts are
+	 * disabled.  How long before apm enables them?
+	 */
 	call	_apm_cpu_idle
 	call	_apm_cpu_busy
 #else
@@ -294,24 +300,24 @@ ENTRY(cpu_switch)
 	movl	%esi,PCB_ESI(%ecx)
 	movl	%edi,PCB_EDI(%ecx)
 
+	movb	_intr_nesting_level,%al
+	movb	%al,PCB_INL(%ecx)
+
 #if NNPX > 0
 	/* have we used fp, and need a save? */
 	mov	_curproc,%eax
 	cmp	%eax,_npxproc
 	jne	1f
-	pushl	%ecx				/* h/w bugs make saving complicated */
-	leal	PCB_SAVEFPU(%ecx),%eax
-	pushl	%eax
+	addl	$PCB_SAVEFPU,%ecx		/* h/w bugs make saving complicated */
+	pushl	%ecx
 	call	_npxsave			/* do it in a big C function */
 	popl	%eax
-	popl	%ecx
 1:
 #endif	/* NNPX > 0 */
 
-	movl	$0,_curproc			/*  out of process */
+	movb	$1,_intr_nesting_level		/* charge Intr, not Sys/Idle */
 
-#	movw	_cpl,%ax
-#	movw	%ax,PCB_IML(%ecx)		/* save ipl */
+	movl	$0,_curproc			/* out of process */
 
 	/* save is done, now choose a new process or idle */
 sw1:
@@ -436,8 +442,11 @@ swtch_com:
 	movl	PCB_EIP(%edx),%eax
 	movl	%eax,(%esp)
 
-	movl	%ecx,_curproc			/* into next process */
 	movl	%edx,_curpcb
+	movl	%ecx,_curproc			/* into next process */
+
+	movb	PCB_INL(%edx),%al
+	movb	%al,_intr_nesting_level
 
 #ifdef	USER_LDT
 	cmpl	$0, PCB_USERLDT(%edx)
@@ -454,46 +463,12 @@ swtch_com:
 2:
 #endif
 
-	pushl	%edx				/* save p to return */
-/*
- * XXX - 0.0 forgot to save it - is that why this was commented out in 0.1?
- * I think restoring the cpl is unnecessary, but we must turn off the cli
- * now that spl*() don't do it as a side affect.
- */
-	pushl	PCB_IML(%edx)
 	sti
-#if 0
-	call	_splx
-#endif
-	addl	$4,%esp
-/*
- * XXX - 0.0 gets here via swtch_to_inactive().  I think 0.1 gets here in the
- * same way.  Better return a value.
- */
-	popl	%eax				/* return(p); */
 	ret
 
 ENTRY(mvesp)
 	movl	%esp,%eax
 	ret
-/*
- * struct proc *swtch_to_inactive(struct proc *p);
- *
- * At exit of a process, move off the address space of the
- * process and onto a "safe" one. Then, on a temporary stack
- * return and run code that disposes of the old state.
- * Since this code requires a parameter from the "old" stack,
- * pass it back as a return value.
- */
-ENTRY(swtch_to_inactive)
-	popl	%edx				/* old pc */
-	popl	%eax				/* arg, our return value */
-	movl	_IdlePTD,%ecx
-	movl	%ecx,%cr3			/* good bye address space */
- #write buffer?
-	movl	$tmpstk,%esp			/* temporary stack, compensated for call */
-	MEXITCOUNT
-	jmp	%edx				/* return, execute remainder of cleanup */
 
 /*
  * savectx(pcb, altreturn)
@@ -502,8 +477,6 @@ ENTRY(swtch_to_inactive)
  */
 ENTRY(savectx)
 	movl	4(%esp),%ecx
-	movw	_cpl,%ax
-	movw	%ax,PCB_IML(%ecx)
 	movl	(%esp),%eax
 	movl	%eax,PCB_EIP(%ecx)
 	movl	%ebx,PCB_EBX(%ecx)
diff --git a/sys/amd64/amd64/exception.S b/sys/amd64/amd64/exception.S
index d746f12d5fad..e14934b3d7f7 100644
--- a/sys/amd64/amd64/exception.S
+++ b/sys/amd64/amd64/exception.S
@@ -30,7 +30,7 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- *	$Id: exception.s,v 1.4 1994/08/13 03:49:38 wollman Exp $
+ *	$Id: exception.s,v 1.5 1994/09/28 03:37:49 bde Exp $
  */
 
 #include "npx.h"				/* NNPX */
@@ -130,9 +130,11 @@ IDTVEC(rsvd)
 IDTVEC(fpu)
 #if NNPX > 0
 	/*
-	 * Handle like an interrupt so that we can call npxintr to clear the
-	 * error.  It would be better to handle npx interrupts as traps but
-	 * this is difficult for nested interrupts.
+	 * Handle like an interrupt (except for accounting) so that we can
+	 * call npxintr to clear the error.  It would be better to handle
+	 * npx interrupts as traps.  This used to be difficult for nested
+	 * interrupts, but now it is fairly easy - mask nested ones the
+	 * same as SWI_AST's.
 	 */
 	pushl	$0				/* dumby error code */
 	pushl	$0				/* dumby trap type */
@@ -150,6 +152,7 @@ IDTVEC(fpu)
 	orl	$SWI_AST_MASK,%eax
 	movl	%eax,_cpl
 	call	_npxintr
+	incb	_intr_nesting_level
 	MEXITCOUNT
 	jmp	_doreti
 #else	/* NNPX > 0 */
@@ -217,6 +220,7 @@ calltrap:
 	 */
 	pushl	%eax
 	subl	$4,%esp
+	incb	_intr_nesting_level
 	MEXITCOUNT
 	jmp	_doreti
 
@@ -265,6 +269,7 @@ IDTVEC(syscall)
 	 */
 	pushl	$0				/* cpl to restore */
 	subl	$4,%esp
+	movb	$1,_intr_nesting_level
 	MEXITCOUNT
 	jmp	_doreti
 
diff --git a/sys/amd64/amd64/exception.s b/sys/amd64/amd64/exception.s
index d746f12d5fad..e14934b3d7f7 100644
--- a/sys/amd64/amd64/exception.s
+++ b/sys/amd64/amd64/exception.s
@@ -30,7 +30,7 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- *	$Id: exception.s,v 1.4 1994/08/13 03:49:38 wollman Exp $
+ *	$Id: exception.s,v 1.5 1994/09/28 03:37:49 bde Exp $
  */
 
 #include "npx.h"				/* NNPX */
@@ -130,9 +130,11 @@ IDTVEC(rsvd)
 IDTVEC(fpu)
 #if NNPX > 0
 	/*
-	 * Handle like an interrupt so that we can call npxintr to clear the
-	 * error.  It would be better to handle npx interrupts as traps but
-	 * this is difficult for nested interrupts.
+	 * Handle like an interrupt (except for accounting) so that we can
+	 * call npxintr to clear the error.  It would be better to handle
+	 * npx interrupts as traps.  This used to be difficult for nested
+	 * interrupts, but now it is fairly easy - mask nested ones the
+	 * same as SWI_AST's.
 	 */
 	pushl	$0				/* dumby error code */
 	pushl	$0				/* dumby trap type */
@@ -150,6 +152,7 @@ IDTVEC(fpu)
 	orl	$SWI_AST_MASK,%eax
 	movl	%eax,_cpl
 	call	_npxintr
+	incb	_intr_nesting_level
 	MEXITCOUNT
 	jmp	_doreti
 #else	/* NNPX > 0 */
@@ -217,6 +220,7 @@ calltrap:
 	 */
 	pushl	%eax
 	subl	$4,%esp
+	incb	_intr_nesting_level
 	MEXITCOUNT
 	jmp	_doreti
 
@@ -265,6 +269,7 @@ IDTVEC(syscall)
 	 */
 	pushl	$0				/* cpl to restore */
 	subl	$4,%esp
+	movb	$1,_intr_nesting_level
 	MEXITCOUNT
 	jmp	_doreti
 
diff --git a/sys/amd64/amd64/genassym.c b/sys/amd64/amd64/genassym.c
index d3cd26d665a8..585c3198d2fc 100644
--- a/sys/amd64/amd64/genassym.c
+++ b/sys/amd64/amd64/genassym.c
@@ -34,7 +34,7 @@
  * SUCH DAMAGE.
  *
  *	from: @(#)genassym.c	5.11 (Berkeley) 5/10/91
- *	$Id: genassym.c,v 1.19 1994/10/26 22:01:11 bde Exp $
+ *	$Id: genassym.c,v 1.20 1994/11/18 05:27:32 phk Exp $
  */
 
 #include <stdio.h>
@@ -164,8 +164,7 @@ main()
 	printf("#define\tPCB_SAVEFPU %d\n", &pcb->pcb_savefpu);
 	printf("#define\tFP_USESEMC %d\n", FP_USESEMC);
 	printf("#define\tPCB_SAVEEMC %d\n", &pcb->pcb_saveemc);
-	printf("#define\tPCB_CMAP2 %d\n", &pcb->pcb_cmap2);
-	printf("#define\tPCB_IML %d\n", &pcb->pcb_iml);
+	printf("#define\tPCB_INL %d\n", &pcb->pcb_inl);
 	printf("#define\tPCB_ONFAULT %d\n", &pcb->pcb_onfault);
 
 	printf("#define\tTF_ES %d\n", &tf->tf_es);
diff --git a/sys/amd64/amd64/swtch.s b/sys/amd64/amd64/swtch.s
index 571d9c9dbc8b..62a970296c26 100644
--- a/sys/amd64/amd64/swtch.s
+++ b/sys/amd64/amd64/swtch.s
@@ -33,7 +33,7 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- *	$Id: swtch.s,v 1.16 1994/10/25 07:25:56 davidg Exp $
+ *	$Id: swtch.s,v 1.17 1994/10/30 20:09:13 bde Exp $
  */
 
 #include "npx.h"	/* for NNPX */
@@ -250,13 +250,19 @@ _idle:
 	ALIGN_TEXT
 idle_loop:
 	cli
+	movb	$1,_intr_nesting_level		/* charge Intr if we leave */
 	cmpl	$0,_whichrtqs			/* real-time queue */
 	jne	sw1a
 	cmpl	$0,_whichqs			/* normal queue */
 	jne	nortqr
 	cmpl	$0,_whichidqs			/* 'idle' queue */
 	jne	idqr
+	movb	$0,_intr_nesting_level		/* charge Idle for this loop */
 #ifdef APM
+	/*
+	 * XXX it breaks the rules to call a function while interrupts are
+	 * disabled.  How long before apm enables them?
+	 */
 	call	_apm_cpu_idle
 	call	_apm_cpu_busy
 #else
@@ -294,24 +300,24 @@ ENTRY(cpu_switch)
 	movl	%esi,PCB_ESI(%ecx)
 	movl	%edi,PCB_EDI(%ecx)
 
+	movb	_intr_nesting_level,%al
+	movb	%al,PCB_INL(%ecx)
+
 #if NNPX > 0
 	/* have we used fp, and need a save? */
 	mov	_curproc,%eax
 	cmp	%eax,_npxproc
 	jne	1f
-	pushl	%ecx				/* h/w bugs make saving complicated */
-	leal	PCB_SAVEFPU(%ecx),%eax
-	pushl	%eax
+	addl	$PCB_SAVEFPU,%ecx		/* h/w bugs make saving complicated */
+	pushl	%ecx
 	call	_npxsave			/* do it in a big C function */
 	popl	%eax
-	popl	%ecx
 1:
 #endif	/* NNPX > 0 */
 
-	movl	$0,_curproc			/*  out of process */
+	movb	$1,_intr_nesting_level		/* charge Intr, not Sys/Idle */
 
-#	movw	_cpl,%ax
-#	movw	%ax,PCB_IML(%ecx)		/* save ipl */
+	movl	$0,_curproc			/* out of process */
 
 	/* save is done, now choose a new process or idle */
 sw1:
@@ -436,8 +442,11 @@ swtch_com:
 	movl	PCB_EIP(%edx),%eax
 	movl	%eax,(%esp)
 
-	movl	%ecx,_curproc			/* into next process */
 	movl	%edx,_curpcb
+	movl	%ecx,_curproc			/* into next process */
+
+	movb	PCB_INL(%edx),%al
+	movb	%al,_intr_nesting_level
 
 #ifdef	USER_LDT
 	cmpl	$0, PCB_USERLDT(%edx)
@@ -454,46 +463,12 @@ swtch_com:
 2:
 #endif
 
-	pushl	%edx				/* save p to return */
-/*
- * XXX - 0.0 forgot to save it - is that why this was commented out in 0.1?
- * I think restoring the cpl is unnecessary, but we must turn off the cli
- * now that spl*() don't do it as a side affect.
- */
-	pushl	PCB_IML(%edx)
 	sti
-#if 0
-	call	_splx
-#endif
-	addl	$4,%esp
-/*
- * XXX - 0.0 gets here via swtch_to_inactive().  I think 0.1 gets here in the
- * same way.  Better return a value.
- */
-	popl	%eax				/* return(p); */
 	ret
 
 ENTRY(mvesp)
 	movl	%esp,%eax
 	ret
-/*
- * struct proc *swtch_to_inactive(struct proc *p);
- *
- * At exit of a process, move off the address space of the
- * process and onto a "safe" one. Then, on a temporary stack
- * return and run code that disposes of the old state.
- * Since this code requires a parameter from the "old" stack,
- * pass it back as a return value.
- */
-ENTRY(swtch_to_inactive)
-	popl	%edx				/* old pc */
-	popl	%eax				/* arg, our return value */
-	movl	_IdlePTD,%ecx
-	movl	%ecx,%cr3			/* good bye address space */
- #write buffer?
-	movl	$tmpstk,%esp			/* temporary stack, compensated for call */
-	MEXITCOUNT
-	jmp	%edx				/* return, execute remainder of cleanup */
 
 /*
  * savectx(pcb, altreturn)
@@ -502,8 +477,6 @@ ENTRY(swtch_to_inactive)
  */
 ENTRY(savectx)
 	movl	4(%esp),%ecx
-	movw	_cpl,%ax
-	movw	%ax,PCB_IML(%ecx)
 	movl	(%esp),%eax
 	movl	%eax,PCB_EIP(%ecx)
 	movl	%ebx,PCB_EBX(%ecx)
diff --git a/sys/amd64/include/cpu.h b/sys/amd64/include/cpu.h
index 79c80af109d2..5d4ce70bc11f 100644
--- a/sys/amd64/include/cpu.h
+++ b/sys/amd64/include/cpu.h
@@ -34,7 +34,7 @@
  * SUCH DAMAGE.
  *
  *	from: @(#)cpu.h	5.4 (Berkeley) 5/9/91
- *	$Id: cpu.h,v 1.16 1994/11/05 22:44:34 bde Exp $
+ *	$Id: cpu.h,v 1.17 1994/11/26 09:27:58 phk Exp $
  */
 
 #ifndef _MACHINE_CPU_H_
@@ -58,8 +58,8 @@
 #define cpu_set_init_frame(p, fp)	(p)->p_md.md_regs = fp
 
 #define	CLKF_USERMODE(framep)	(ISPL((framep)->cf_cs) == SEL_UPL)
-#define CLKF_INTR(framep)	(0)
-#if 0
+#define CLKF_INTR(framep)	(intr_nesting_level >= 2)
+#if 1
 /*
  * XXX splsoftclock() is very broken and barely worth fixing.  It doesn't
  * turn off the clock bit in imen or in the icu.  (This is not a serious
@@ -127,6 +127,7 @@ struct cpu_nameclass {
 extern int	bootverbose;
 extern int	cpu;
 extern int	cpu_class;
+extern u_char	intr_nesting_level;
 extern struct cpu_nameclass i386_cpus[];
 extern int	want_resched;	/* resched was called */
 
diff --git a/sys/amd64/include/pcb.h b/sys/amd64/include/pcb.h
index 37b76f85832d..8ce7febb5ada 100644
--- a/sys/amd64/include/pcb.h
+++ b/sys/amd64/include/pcb.h
@@ -34,7 +34,7 @@
  * SUCH DAMAGE.
  *
  *	from: @(#)pcb.h	5.10 (Berkeley) 5/12/91
- *	$Id: pcb.h,v 1.6 1994/08/13 03:49:50 wollman Exp $
+ *	$Id: pcb.h,v 1.7 1994/10/08 22:21:33 phk Exp $
  */
 
 #ifndef _I386_PCB_H_
@@ -73,10 +73,10 @@ struct pcb {
 #endif
 #define	FP_USESEMC	0x08	/* process uses EMC memory-mapped mode */
 #define	FP_SOFTFP	0x20	/* process using software fltng pnt emulator */
-	short	pcb_iml;	/* interrupt mask level */
+	u_char	pcb_inl;	/* intr_nesting_level at context switch */
 	caddr_t	pcb_onfault;	/* copyin/out fault recovery */
 	long	pcb_sigc[8];	/* XXX signal code trampoline */
-	int	pcb_cmap2;	/* XXX temporary PTE - will prefault instead */
+	int	pad2;		/* XXX unused - remove it if you change struct */
 };
 
 /*
diff --git a/sys/amd64/isa/vector.S b/sys/amd64/isa/vector.S
index 1bc2324f62d9..fcd0a7711d2a 100644
--- a/sys/amd64/isa/vector.S
+++ b/sys/amd64/isa/vector.S
@@ -1,6 +1,6 @@
 /*
  *	from: vector.s, 386BSD 0.1 unknown origin
- *	$Id: vector.s,v 1.9 1994/09/20 21:35:49 bde Exp $
+ *	$Id: vector.s,v 1.10 1994/11/01 23:29:50 bde Exp $
  */
 
 #include <i386/isa/icu.h>
@@ -147,6 +147,7 @@ IDTVEC(fastintr/**/irq_num) ; \
 	movl	(2+8+1)*4(%esp),%eax ;	/* ... cpl from thin frame */ \
 	pushl	%eax ; \
 	subl	$4,%esp ;	/* junk for unit number */ \
+	incb	_intr_nesting_level ; \
 	MEXITCOUNT ; \
 	jmp	_doreti
 
@@ -172,7 +173,7 @@ IDTVEC(intr/**/irq_num) ; \
 	movl	_cpl,%eax ; \
 	testb	$IRQ_BIT(irq_num),%reg ; \
 	jne	2f ; \
-1: ; \
+	incb	_intr_nesting_level ; \
 Xresume/**/irq_num: ; \
 	FAKE_MCOUNT(12*4(%esp)) ;	/* XXX late to avoid double count */ \
 	movl	_intr_countp + (irq_num) * 4,%eax ; \
@@ -254,6 +255,10 @@ imasks:				/* masks for interrupt handlers */
 	.space	NHWI*4		/* padding; HWI masks are elsewhere */
 	.long	SWI_TTY_MASK, SWI_NET_MASK, 0, 0, 0, 0, 0, 0
 	.long	0, 0, 0, 0, 0, 0, SWI_CLOCK_MASK, SWI_AST_MASK
+	.globl	_intr_nesting_level
+_intr_nesting_level:
+	.byte	0
+	.space	3
 
 /*
  * Interrupt counters and names.  The format of these and the label names
diff --git a/sys/amd64/isa/vector.s b/sys/amd64/isa/vector.s
index 1bc2324f62d9..fcd0a7711d2a 100644
--- a/sys/amd64/isa/vector.s
+++ b/sys/amd64/isa/vector.s
@@ -1,6 +1,6 @@
 /*
  *	from: vector.s, 386BSD 0.1 unknown origin
- *	$Id: vector.s,v 1.9 1994/09/20 21:35:49 bde Exp $
+ *	$Id: vector.s,v 1.10 1994/11/01 23:29:50 bde Exp $
  */
 
 #include <i386/isa/icu.h>
@@ -147,6 +147,7 @@ IDTVEC(fastintr/**/irq_num) ; \
 	movl	(2+8+1)*4(%esp),%eax ;	/* ... cpl from thin frame */ \
 	pushl	%eax ; \
 	subl	$4,%esp ;	/* junk for unit number */ \
+	incb	_intr_nesting_level ; \
 	MEXITCOUNT ; \
 	jmp	_doreti
 
@@ -172,7 +173,7 @@ IDTVEC(intr/**/irq_num) ; \
 	movl	_cpl,%eax ; \
 	testb	$IRQ_BIT(irq_num),%reg ; \
 	jne	2f ; \
-1: ; \
+	incb	_intr_nesting_level ; \
 Xresume/**/irq_num: ; \
 	FAKE_MCOUNT(12*4(%esp)) ;	/* XXX late to avoid double count */ \
 	movl	_intr_countp + (irq_num) * 4,%eax ; \
@@ -254,6 +255,10 @@ imasks:				/* masks for interrupt handlers */
 	.space	NHWI*4		/* padding; HWI masks are elsewhere */
 	.long	SWI_TTY_MASK, SWI_NET_MASK, 0, 0, 0, 0, 0, 0
 	.long	0, 0, 0, 0, 0, 0, SWI_CLOCK_MASK, SWI_AST_MASK
+	.globl	_intr_nesting_level
+_intr_nesting_level:
+	.byte	0
+	.space	3
 
 /*
  * Interrupt counters and names.  The format of these and the label names
diff --git a/sys/i386/i386/exception.s b/sys/i386/i386/exception.s
index d746f12d5fad..e14934b3d7f7 100644
--- a/sys/i386/i386/exception.s
+++ b/sys/i386/i386/exception.s
@@ -30,7 +30,7 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- *	$Id: exception.s,v 1.4 1994/08/13 03:49:38 wollman Exp $
+ *	$Id: exception.s,v 1.5 1994/09/28 03:37:49 bde Exp $
  */
 
 #include "npx.h"				/* NNPX */
@@ -130,9 +130,11 @@ IDTVEC(rsvd)
 IDTVEC(fpu)
 #if NNPX > 0
 	/*
-	 * Handle like an interrupt so that we can call npxintr to clear the
-	 * error.  It would be better to handle npx interrupts as traps but
-	 * this is difficult for nested interrupts.
+	 * Handle like an interrupt (except for accounting) so that we can
+	 * call npxintr to clear the error.  It would be better to handle
+	 * npx interrupts as traps.  This used to be difficult for nested
+	 * interrupts, but now it is fairly easy - mask nested ones the
+	 * same as SWI_AST's.
 	 */
 	pushl	$0				/* dumby error code */
 	pushl	$0				/* dumby trap type */
@@ -150,6 +152,7 @@ IDTVEC(fpu)
 	orl	$SWI_AST_MASK,%eax
 	movl	%eax,_cpl
 	call	_npxintr
+	incb	_intr_nesting_level
 	MEXITCOUNT
 	jmp	_doreti
 #else	/* NNPX > 0 */
@@ -217,6 +220,7 @@ calltrap:
 	 */
 	pushl	%eax
 	subl	$4,%esp
+	incb	_intr_nesting_level
 	MEXITCOUNT
 	jmp	_doreti
 
@@ -265,6 +269,7 @@ IDTVEC(syscall)
 	 */
 	pushl	$0				/* cpl to restore */
 	subl	$4,%esp
+	movb	$1,_intr_nesting_level
 	MEXITCOUNT
 	jmp	_doreti
 
diff --git a/sys/i386/i386/genassym.c b/sys/i386/i386/genassym.c
index d3cd26d665a8..585c3198d2fc 100644
--- a/sys/i386/i386/genassym.c
+++ b/sys/i386/i386/genassym.c
@@ -34,7 +34,7 @@
  * SUCH DAMAGE.
  *
  *	from: @(#)genassym.c	5.11 (Berkeley) 5/10/91
- *	$Id: genassym.c,v 1.19 1994/10/26 22:01:11 bde Exp $
+ *	$Id: genassym.c,v 1.20 1994/11/18 05:27:32 phk Exp $
  */
 
 #include <stdio.h>
@@ -164,8 +164,7 @@ main()
 	printf("#define\tPCB_SAVEFPU %d\n", &pcb->pcb_savefpu);
 	printf("#define\tFP_USESEMC %d\n", FP_USESEMC);
 	printf("#define\tPCB_SAVEEMC %d\n", &pcb->pcb_saveemc);
-	printf("#define\tPCB_CMAP2 %d\n", &pcb->pcb_cmap2);
-	printf("#define\tPCB_IML %d\n", &pcb->pcb_iml);
+	printf("#define\tPCB_INL %d\n", &pcb->pcb_inl);
 	printf("#define\tPCB_ONFAULT %d\n", &pcb->pcb_onfault);
 
 	printf("#define\tTF_ES %d\n", &tf->tf_es);
diff --git a/sys/i386/i386/swtch.s b/sys/i386/i386/swtch.s
index 571d9c9dbc8b..62a970296c26 100644
--- a/sys/i386/i386/swtch.s
+++ b/sys/i386/i386/swtch.s
@@ -33,7 +33,7 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- *	$Id: swtch.s,v 1.16 1994/10/25 07:25:56 davidg Exp $
+ *	$Id: swtch.s,v 1.17 1994/10/30 20:09:13 bde Exp $
  */
 
 #include "npx.h"	/* for NNPX */
@@ -250,13 +250,19 @@ _idle:
 	ALIGN_TEXT
 idle_loop:
 	cli
+	movb	$1,_intr_nesting_level		/* charge Intr if we leave */
 	cmpl	$0,_whichrtqs			/* real-time queue */
 	jne	sw1a
 	cmpl	$0,_whichqs			/* normal queue */
 	jne	nortqr
 	cmpl	$0,_whichidqs			/* 'idle' queue */
 	jne	idqr
+	movb	$0,_intr_nesting_level		/* charge Idle for this loop */
 #ifdef APM
+	/*
+	 * XXX it breaks the rules to call a function while interrupts are
+	 * disabled.  How long before apm enables them?
+	 */
 	call	_apm_cpu_idle
 	call	_apm_cpu_busy
 #else
@@ -294,24 +300,24 @@ ENTRY(cpu_switch)
 	movl	%esi,PCB_ESI(%ecx)
 	movl	%edi,PCB_EDI(%ecx)
 
+	movb	_intr_nesting_level,%al
+	movb	%al,PCB_INL(%ecx)
+
 #if NNPX > 0
 	/* have we used fp, and need a save? */
 	mov	_curproc,%eax
 	cmp	%eax,_npxproc
 	jne	1f
-	pushl	%ecx				/* h/w bugs make saving complicated */
-	leal	PCB_SAVEFPU(%ecx),%eax
-	pushl	%eax
+	addl	$PCB_SAVEFPU,%ecx		/* h/w bugs make saving complicated */
+	pushl	%ecx
 	call	_npxsave			/* do it in a big C function */
 	popl	%eax
-	popl	%ecx
 1:
 #endif	/* NNPX > 0 */
 
-	movl	$0,_curproc			/*  out of process */
+	movb	$1,_intr_nesting_level		/* charge Intr, not Sys/Idle */
 
-#	movw	_cpl,%ax
-#	movw	%ax,PCB_IML(%ecx)		/* save ipl */
+	movl	$0,_curproc			/* out of process */
 
 	/* save is done, now choose a new process or idle */
 sw1:
@@ -436,8 +442,11 @@ swtch_com:
 	movl	PCB_EIP(%edx),%eax
 	movl	%eax,(%esp)
 
-	movl	%ecx,_curproc			/* into next process */
 	movl	%edx,_curpcb
+	movl	%ecx,_curproc			/* into next process */
+
+	movb	PCB_INL(%edx),%al
+	movb	%al,_intr_nesting_level
 
 #ifdef	USER_LDT
 	cmpl	$0, PCB_USERLDT(%edx)
@@ -454,46 +463,12 @@ swtch_com:
 2:
 #endif
 
-	pushl	%edx				/* save p to return */
-/*
- * XXX - 0.0 forgot to save it - is that why this was commented out in 0.1?
- * I think restoring the cpl is unnecessary, but we must turn off the cli
- * now that spl*() don't do it as a side affect.
- */
-	pushl	PCB_IML(%edx)
 	sti
-#if 0
-	call	_splx
-#endif
-	addl	$4,%esp
-/*
- * XXX - 0.0 gets here via swtch_to_inactive().  I think 0.1 gets here in the
- * same way.  Better return a value.
- */
-	popl	%eax				/* return(p); */
 	ret
 
 ENTRY(mvesp)
 	movl	%esp,%eax
 	ret
-/*
- * struct proc *swtch_to_inactive(struct proc *p);
- *
- * At exit of a process, move off the address space of the
- * process and onto a "safe" one. Then, on a temporary stack
- * return and run code that disposes of the old state.
- * Since this code requires a parameter from the "old" stack,
- * pass it back as a return value.
- */
-ENTRY(swtch_to_inactive)
-	popl	%edx				/* old pc */
-	popl	%eax				/* arg, our return value */
-	movl	_IdlePTD,%ecx
-	movl	%ecx,%cr3			/* good bye address space */
- #write buffer?
-	movl	$tmpstk,%esp			/* temporary stack, compensated for call */
-	MEXITCOUNT
-	jmp	%edx				/* return, execute remainder of cleanup */
 
 /*
  * savectx(pcb, altreturn)
@@ -502,8 +477,6 @@ ENTRY(swtch_to_inactive)
  */
 ENTRY(savectx)
 	movl	4(%esp),%ecx
-	movw	_cpl,%ax
-	movw	%ax,PCB_IML(%ecx)
 	movl	(%esp),%eax
 	movl	%eax,PCB_EIP(%ecx)
 	movl	%ebx,PCB_EBX(%ecx)
diff --git a/sys/i386/include/cpu.h b/sys/i386/include/cpu.h
index 79c80af109d2..5d4ce70bc11f 100644
--- a/sys/i386/include/cpu.h
+++ b/sys/i386/include/cpu.h
@@ -34,7 +34,7 @@
  * SUCH DAMAGE.
  *
  *	from: @(#)cpu.h	5.4 (Berkeley) 5/9/91
- *	$Id: cpu.h,v 1.16 1994/11/05 22:44:34 bde Exp $
+ *	$Id: cpu.h,v 1.17 1994/11/26 09:27:58 phk Exp $
  */
 
 #ifndef _MACHINE_CPU_H_
@@ -58,8 +58,8 @@
 #define cpu_set_init_frame(p, fp)	(p)->p_md.md_regs = fp
 
 #define	CLKF_USERMODE(framep)	(ISPL((framep)->cf_cs) == SEL_UPL)
-#define CLKF_INTR(framep)	(0)
-#if 0
+#define CLKF_INTR(framep)	(intr_nesting_level >= 2)
+#if 1
 /*
  * XXX splsoftclock() is very broken and barely worth fixing.  It doesn't
  * turn off the clock bit in imen or in the icu.  (This is not a serious
@@ -127,6 +127,7 @@ struct cpu_nameclass {
 extern int	bootverbose;
 extern int	cpu;
 extern int	cpu_class;
+extern u_char	intr_nesting_level;
 extern struct cpu_nameclass i386_cpus[];
 extern int	want_resched;	/* resched was called */
 
diff --git a/sys/i386/include/pcb.h b/sys/i386/include/pcb.h
index 37b76f85832d..8ce7febb5ada 100644
--- a/sys/i386/include/pcb.h
+++ b/sys/i386/include/pcb.h
@@ -34,7 +34,7 @@
  * SUCH DAMAGE.
  *
  *	from: @(#)pcb.h	5.10 (Berkeley) 5/12/91
- *	$Id: pcb.h,v 1.6 1994/08/13 03:49:50 wollman Exp $
+ *	$Id: pcb.h,v 1.7 1994/10/08 22:21:33 phk Exp $
  */
 
 #ifndef _I386_PCB_H_
@@ -73,10 +73,10 @@ struct pcb {
 #endif
 #define	FP_USESEMC	0x08	/* process uses EMC memory-mapped mode */
 #define	FP_SOFTFP	0x20	/* process using software fltng pnt emulator */
-	short	pcb_iml;	/* interrupt mask level */
+	u_char	pcb_inl;	/* intr_nesting_level at context switch */
 	caddr_t	pcb_onfault;	/* copyin/out fault recovery */
 	long	pcb_sigc[8];	/* XXX signal code trampoline */
-	int	pcb_cmap2;	/* XXX temporary PTE - will prefault instead */
+	int	pad2;		/* XXX unused - remove it if you change struct */
 };
 
 /*
diff --git a/sys/i386/isa/icu.s b/sys/i386/isa/icu.s
index bd0d014c4918..c8cf81b2139c 100644
--- a/sys/i386/isa/icu.s
+++ b/sys/i386/isa/icu.s
@@ -36,7 +36,7 @@
  *
  *	@(#)icu.s	7.2 (Berkeley) 5/21/91
  *
- *	$Id: icu.s,v 1.14 1994/09/19 22:24:31 wollman Exp $
+ *	$Id: icu.s,v 1.15 1994/09/20 21:35:47 bde Exp $
  */
 
 /*
@@ -102,6 +102,7 @@ doreti_next:
 	jne	doreti_unpend
 doreti_exit:
 	movl	%eax,_cpl
+	decb	_intr_nesting_level
 	MEXITCOUNT
 	popl	%es
 	popl	%ds
diff --git a/sys/i386/isa/vector.s b/sys/i386/isa/vector.s
index 1bc2324f62d9..fcd0a7711d2a 100644
--- a/sys/i386/isa/vector.s
+++ b/sys/i386/isa/vector.s
@@ -1,6 +1,6 @@
 /*
  *	from: vector.s, 386BSD 0.1 unknown origin
- *	$Id: vector.s,v 1.9 1994/09/20 21:35:49 bde Exp $
+ *	$Id: vector.s,v 1.10 1994/11/01 23:29:50 bde Exp $
  */
 
 #include <i386/isa/icu.h>
@@ -147,6 +147,7 @@ IDTVEC(fastintr/**/irq_num) ; \
 	movl	(2+8+1)*4(%esp),%eax ;	/* ... cpl from thin frame */ \
 	pushl	%eax ; \
 	subl	$4,%esp ;	/* junk for unit number */ \
+	incb	_intr_nesting_level ; \
 	MEXITCOUNT ; \
 	jmp	_doreti
 
@@ -172,7 +173,7 @@ IDTVEC(intr/**/irq_num) ; \
 	movl	_cpl,%eax ; \
 	testb	$IRQ_BIT(irq_num),%reg ; \
 	jne	2f ; \
-1: ; \
+	incb	_intr_nesting_level ; \
 Xresume/**/irq_num: ; \
 	FAKE_MCOUNT(12*4(%esp)) ;	/* XXX late to avoid double count */ \
 	movl	_intr_countp + (irq_num) * 4,%eax ; \
@@ -254,6 +255,10 @@ imasks:				/* masks for interrupt handlers */
 	.space	NHWI*4		/* padding; HWI masks are elsewhere */
 	.long	SWI_TTY_MASK, SWI_NET_MASK, 0, 0, 0, 0, 0, 0
 	.long	0, 0, 0, 0, 0, 0, SWI_CLOCK_MASK, SWI_AST_MASK
+	.globl	_intr_nesting_level
+_intr_nesting_level:
+	.byte	0
+	.space	3
 
 /*
  * Interrupt counters and names.  The format of these and the label names