From 431d0feffbaa4f5e66b1f9646d2bb780a99daf3f Mon Sep 17 00:00:00 2001
From: Matthew Dillon <dillon@dragonflybsd.org>
Date: Tue, 9 Jan 2007 23:34:06 +0000
Subject: [PATCH] Get floating point working in virtual kernels.  Add a feature
 that allows the virtual kernel to request that the real kernel return a T_DNA
 fault if an emulated user context attempts to use the FP unit.

---
 sys/cpu/i386/include/npx.h             |  5 +--
 sys/cpu/i386/include/pmap.h            | 15 +++++--
 sys/cpu/i386/include/vframe.h          |  9 +---
 sys/platform/pc32/i386/bcopy.s         |  5 ++-
 sys/platform/pc32/i386/trap.c          | 43 +++++++++++++++++-
 sys/platform/pc32/include/md_var.h     |  3 +-
 sys/platform/pc32/include/pcb.h        |  3 +-
 sys/platform/pc32/isa/npx.c            |  9 +---
 sys/platform/vkernel/i386/npx.c        | 16 +++----
 sys/platform/vkernel/i386/trap.c       | 60 ++++++++++++++++++++++++--
 sys/platform/vkernel/i386/vm_machdep.c |  4 +-
 sys/platform/vkernel/include/md_var.h  |  3 +-
 sys/platform/vkernel/include/pcb.h     |  5 ++-
 sys/sys/systm.h                        |  3 +-
 sys/vm/vm_vmspace.c                    |  3 +-
 15 files changed, 140 insertions(+), 46 deletions(-)

diff --git a/sys/cpu/i386/include/npx.h b/sys/cpu/i386/include/npx.h
index c7adee5bca..afbff239bd 100644
--- a/sys/cpu/i386/include/npx.h
+++ b/sys/cpu/i386/include/npx.h
@@ -35,7 +35,7 @@
  *
  *	from: @(#)npx.h	5.3 (Berkeley) 1/18/91
  * $FreeBSD: src/sys/i386/include/npx.h,v 1.18.2.1 2001/08/15 01:23:52 peter Exp $
- * $DragonFly: src/sys/cpu/i386/include/npx.h,v 1.11 2007/01/08 03:33:37 dillon Exp $
+ * $DragonFly: src/sys/cpu/i386/include/npx.h,v 1.12 2007/01/09 23:34:01 dillon Exp $
  */
 
 /*
@@ -151,12 +151,11 @@ union	savefpu {
 #ifdef _KERNEL
 
 struct proc;
+struct trapframe;
 
-int	npxdna (void);
 void	npxexit (void);
 void	npxinit (u_short control);
 void	npxsave (union savefpu *addr);
-void	npxsync (void);
 #endif
 
 #endif /* !_CPU_NPX_H_ */
diff --git a/sys/cpu/i386/include/pmap.h b/sys/cpu/i386/include/pmap.h
index 796adc6633..0a0fb5d308 100644
--- a/sys/cpu/i386/include/pmap.h
+++ b/sys/cpu/i386/include/pmap.h
@@ -43,7 +43,7 @@
  *	from: hp300: @(#)pmap.h	7.2 (Berkeley) 12/16/90
  *	from: @(#)pmap.h	7.4 (Berkeley) 5/12/91
  * $FreeBSD: src/sys/i386/include/pmap.h,v 1.65.2.3 2001/10/03 07:15:37 peter Exp $
- * $DragonFly: src/sys/cpu/i386/include/pmap.h,v 1.12 2006/11/07 06:43:22 dillon Exp $
+ * $DragonFly: src/sys/cpu/i386/include/pmap.h,v 1.13 2007/01/09 23:34:01 dillon Exp $
  */
 
 #ifndef _CPU_PMAP_H_
@@ -76,11 +76,20 @@
 #define PG_N		(PG_NC_PWT|PG_NC_PCD)	/* Non-cacheable */
 
 /*
- * Page Protection Exception bits
+ * Page Protection Exception bits, stored in tf_err on a real fault
+ * and in tf_xflags on a signal frame or virtual kernel's trap frame.
+ * These only apply to T_PAGEFLT faults.
  */
-
 #define PGEX_P		0x01	/* Protection violation vs. not present */
 #define PGEX_W		0x02	/* during a Write cycle */
 #define PGEX_U		0x04	/* access from User mode (UPL) */
 
+/*
+ * Virtual kernel bits, managed by software.
+ *
+ * FPEX_FAULT -	Force the FP unit to generate a T_DNA fault if an emulated
+ *		user process tried to use it.
+ */
+#define FPEX_FAULT	0x80
+
 #endif /* !_CPU_PMAP_H_ */
diff --git a/sys/cpu/i386/include/vframe.h b/sys/cpu/i386/include/vframe.h
index f7ea20da52..ab1646204d 100644
--- a/sys/cpu/i386/include/vframe.h
+++ b/sys/cpu/i386/include/vframe.h
@@ -31,7 +31,7 @@
  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  * 
- * $DragonFly: src/sys/cpu/i386/include/vframe.h,v 1.1 2007/01/08 16:34:10 dillon Exp $
+ * $DragonFly: src/sys/cpu/i386/include/vframe.h,v 1.2 2007/01/09 23:34:01 dillon Exp $
  */
 
 #ifndef _CPU_VFRAME_H_
@@ -49,15 +49,8 @@
  * addition to trapframe.
  */
 struct vextframe {
-        int     vx_features;    /* enabled features */
-        int     vx_changes;     /* changes made on control transfer */
-        union savefpu vx_fpu;
 	struct savetls vx_tls;
 };
 
-#define VXF_FP87	0x0001
-#define VXF_XMM		0x0002
-#define VXF_TLS		0x0004
-
 #endif
 
diff --git a/sys/platform/pc32/i386/bcopy.s b/sys/platform/pc32/i386/bcopy.s
index 3cdd48bbe1..7ba6a90a4d 100644
--- a/sys/platform/pc32/i386/bcopy.s
+++ b/sys/platform/pc32/i386/bcopy.s
@@ -31,7 +31,7 @@
  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  * 
- * $DragonFly: src/sys/platform/pc32/i386/bcopy.s,v 1.8 2006/06/10 18:07:05 dillon Exp $
+ * $DragonFly: src/sys/platform/pc32/i386/bcopy.s,v 1.9 2007/01/09 23:34:02 dillon Exp $
  */
 /*
  * bcopy(source:%esi, target:%edi, count:%ecx)
@@ -337,6 +337,9 @@ ENTRY(asm_generic_bcopy)
 	 * critical section, because TS may get set by a preemptive
 	 * interrupt.  However, we *can* race a load/set-ts/store against
 	 * an interrupt doing the same thing.
+	 *
+	 * WARNING! A Virtual kernel depends on CR0_TS remaining set after
+	 * we use the FP unit if it asked it to be set.
 	 */
 
 #define MMX_RESTORE_BLOCK			\
diff --git a/sys/platform/pc32/i386/trap.c b/sys/platform/pc32/i386/trap.c
index 52dfb64b37..a5be1fc928 100644
--- a/sys/platform/pc32/i386/trap.c
+++ b/sys/platform/pc32/i386/trap.c
@@ -36,7 +36,7 @@
  *
  *	from: @(#)trap.c	7.4 (Berkeley) 5/13/91
  * $FreeBSD: src/sys/i386/i386/trap.c,v 1.147.2.11 2003/02/27 19:09:59 luoqi Exp $
- * $DragonFly: src/sys/platform/pc32/i386/trap.c,v 1.93 2007/01/09 07:03:32 dillon Exp $
+ * $DragonFly: src/sys/platform/pc32/i386/trap.c,v 1.94 2007/01/09 23:34:02 dillon Exp $
  */
 
 /*
@@ -87,6 +87,7 @@
 #include <machine/pcb.h>
 #include <machine/smp.h>
 #include <machine/tss.h>
+#include <machine/specialreg.h>
 #include <machine/globaldata.h>
 
 #include <machine_base/isa/intr_machdep.h>
@@ -610,6 +611,24 @@ restart:
 			break;
 
 		case T_DNA:
+			/*
+			 * Virtual kernel intercept - pass the DNA exception
+			 * to the virtual kernel if it asked to handle it.
+			 * This occurs when the virtual kernel is holding
+			 * onto the FP context for a different emulated
+			 * process then the one currently running.
+			 *
+			 * We must still call npxdna() since we may have
+			 * saved FP state that the virtual kernel needs
+			 * to hand over to a different emulated process.
+			 */
+			if (p->p_vkernel && p->p_vkernel->vk_current &&
+			    (td->td_pcb->pcb_flags & FP_VIRTFP)
+			) {
+				npxdna();
+				break;
+			}
+
 #if NNPX > 0
 			/* 
 			 * The kernel may have switched out the FP unit's
@@ -1437,3 +1456,25 @@ fork_return(struct lwp *lp, struct trapframe frame)
 	rel_mplock();
 #endif
 }
+
+/*
+ * If FPEX_FAULT is set then set FP_VIRTFP in the PCB to force a T_DNA
+ * fault (which is then passed back to the virtual kernel) if an attempt is
+ * made to use the FP unit.
+ *
+ * XXX this is a fairly big hack.
+ */
+void
+set_vkernel_fp(struct trapframe *frame)
+{
+	struct thread *td = curthread;
+
+	if (frame->tf_xflags & FPEX_FAULT) {
+		td->td_pcb->pcb_flags |= FP_VIRTFP;
+		if (mdcpu->gd_npxthread == td)
+			npxexit();
+	} else {
+		td->td_pcb->pcb_flags &= ~FP_VIRTFP;
+	}
+}
+
diff --git a/sys/platform/pc32/include/md_var.h b/sys/platform/pc32/include/md_var.h
index 0417f33bc6..bef1113405 100644
--- a/sys/platform/pc32/include/md_var.h
+++ b/sys/platform/pc32/include/md_var.h
@@ -27,7 +27,7 @@
  * SUCH DAMAGE.
  *
  * $FreeBSD: src/sys/i386/include/md_var.h,v 1.35.2.4 2003/01/22 20:14:53 jhb Exp $
- * $DragonFly: src/sys/platform/pc32/include/md_var.h,v 1.24 2007/01/08 03:33:42 dillon Exp $
+ * $DragonFly: src/sys/platform/pc32/include/md_var.h,v 1.25 2007/01/09 23:34:03 dillon Exp $
  */
 
 #ifndef _MACHINE_MD_VAR_H_
@@ -112,5 +112,6 @@ void	setidt (int idx, alias_for_inthand_t *func, int typ, int dpl,
 		    int selec);
 void	userconfig (void);
 int     user_dbreg_trap (void);
+int     npxdna(void);
 
 #endif /* !_MACHINE_MD_VAR_H_ */
diff --git a/sys/platform/pc32/include/pcb.h b/sys/platform/pc32/include/pcb.h
index 3e401807da..c0aabf1d07 100644
--- a/sys/platform/pc32/include/pcb.h
+++ b/sys/platform/pc32/include/pcb.h
@@ -35,7 +35,7 @@
  *
  *	from: @(#)pcb.h	5.10 (Berkeley) 5/12/91
  * $FreeBSD: src/sys/i386/include/pcb.h,v 1.32.2.1 2001/08/15 01:23:52 peter Exp $
- * $DragonFly: src/sys/platform/pc32/include/pcb.h,v 1.11 2007/01/08 03:33:42 dillon Exp $
+ * $DragonFly: src/sys/platform/pc32/include/pcb.h,v 1.12 2007/01/09 23:34:03 dillon Exp $
  */
 
 #ifndef _MACHINE_PCB_H_
@@ -67,6 +67,7 @@ struct pcb {
 	u_char	pcb_flags;
 #define	FP_SOFTFP	0x01	/* process using software fltng pnt emulator */
 #define	PCB_DBREGS	0x02	/* process using debug registers */
+#define FP_VIRTFP	0x04	/* virtual kernel wants exception */
 	caddr_t	pcb_onfault;	/* copyin/out fault recovery */
 	int	pcb_unused;
 	struct	pcb_ext	*pcb_ext;	/* optional pcb extension */
diff --git a/sys/platform/pc32/isa/npx.c b/sys/platform/pc32/isa/npx.c
index b2482cd837..5d534f48e3 100644
--- a/sys/platform/pc32/isa/npx.c
+++ b/sys/platform/pc32/isa/npx.c
@@ -33,7 +33,7 @@
  *
  *	from: @(#)npx.c	7.2 (Berkeley) 5/12/91
  * $FreeBSD: src/sys/i386/isa/npx.c,v 1.80.2.3 2001/10/20 19:04:38 tegge Exp $
- * $DragonFly: src/sys/platform/pc32/isa/npx.c,v 1.39 2007/01/08 03:33:43 dillon Exp $
+ * $DragonFly: src/sys/platform/pc32/isa/npx.c,v 1.40 2007/01/09 23:34:04 dillon Exp $
  */
 
 #include "opt_cpu.h"
@@ -975,13 +975,6 @@ fpusave(union savefpu *addr)
 		fnsave(addr);
 }
 
-void
-npxsync(void)
-{
-	if (curthread == mdcpu->gd_npxthread)
-		npxsave(curthread->td_savefpu);
-}
-
 #ifndef CPU_DISABLE_SSE
 /*
  * On AuthenticAMD processors, the fxrstor instruction does not restore
diff --git a/sys/platform/vkernel/i386/npx.c b/sys/platform/vkernel/i386/npx.c
index c462d29265..5d5124fdca 100644
--- a/sys/platform/vkernel/i386/npx.c
+++ b/sys/platform/vkernel/i386/npx.c
@@ -36,7 +36,7 @@
  * 
  * from: @(#)npx.c	7.2 (Berkeley) 5/12/91
  * $FreeBSD: src/sys/i386/isa/npx.c,v 1.80.2.3 2001/10/20 19:04:38 tegge Exp $
- * $DragonFly: src/sys/platform/vkernel/i386/npx.c,v 1.3 2007/01/08 03:33:43 dillon Exp $
+ * $DragonFly: src/sys/platform/vkernel/i386/npx.c,v 1.4 2007/01/09 23:34:05 dillon Exp $
  */
 
 #include "opt_debug_npx.h"
@@ -102,7 +102,6 @@ static	void	fpu_clean_state(void);
 int cpu_fxsr = 0;
 
 static	int	npx_attach	(device_t dev);
-	void	npx_intr	(void *);
 static	void	fpusave		(union savefpu *);
 static	void	fpurstor	(union savefpu *);
 
@@ -326,6 +325,8 @@ static char fpetable[128] = {
 	FPE_FLTSUB,	/* 7F - INV | DNML | DZ | OFL | UFL | IMP | STK */
 };
 
+#if 0
+
 /*
  * Preserve the FP status word, clear FP exceptions, then generate a SIGFPE.
  *
@@ -441,6 +442,8 @@ npx_intr(void *dummy)
 	crit_exit();
 }
 
+#endif
+
 /*
  * Implement the device not available (DNA) exception.  gd_npxthread had 
  * better be NULL.  Restore the current thread's FP state and set gd_npxthread
@@ -450,7 +453,7 @@ npx_intr(void *dummy)
  * section to stabilize the FP state.
  */
 int
-npxdna(void)
+npxdna(struct trapframe *frame)
 {
 	u_long *exstat;
 
@@ -533,13 +536,6 @@ fpusave(union savefpu *addr)
 		fnsave(addr);
 }
 
-void
-npxsync(void)
-{
-	if (curthread == mdcpu->gd_npxthread)
-		npxsave(curthread->td_savefpu);
-}
-
 #ifndef CPU_DISABLE_SSE
 /*
  * On AuthenticAMD processors, the fxrstor instruction does not restore
diff --git a/sys/platform/vkernel/i386/trap.c b/sys/platform/vkernel/i386/trap.c
index e998226e66..649ac6c504 100644
--- a/sys/platform/vkernel/i386/trap.c
+++ b/sys/platform/vkernel/i386/trap.c
@@ -36,7 +36,7 @@
  *
  *	from: @(#)trap.c	7.4 (Berkeley) 5/13/91
  * $FreeBSD: src/sys/i386/i386/trap.c,v 1.147.2.11 2003/02/27 19:09:59 luoqi Exp $
- * $DragonFly: src/sys/platform/vkernel/i386/trap.c,v 1.7 2007/01/09 07:23:02 dillon Exp $
+ * $DragonFly: src/sys/platform/vkernel/i386/trap.c,v 1.8 2007/01/09 23:34:05 dillon Exp $
  */
 
 /*
@@ -533,6 +533,23 @@ restart:
 		break;
 
 	case T_DNA:
+		/*
+		 * Virtual kernel intercept - pass the DNA exception
+		 * to the (emulated) virtual kernel if it asked to handle 
+		 * it.  This occurs when the virtual kernel is holding
+		 * onto the FP context for a different emulated
+		 * process then the one currently running.
+		 *
+		 * We must still call npxdna() since we may have
+		 * saved FP state that the (emulated) virtual kernel
+		 * needs to hand over to a different emulated process.
+		 */
+		if (p->p_vkernel && p->p_vkernel->vk_current &&
+		    (td->td_pcb->pcb_flags & FP_VIRTFP)
+		) {
+			npxdna(frame);
+			break;
+		}
 #if NNPX > 0
 		/* 
 		 * The kernel may have switched out the FP unit's
@@ -540,7 +557,7 @@ restart:
 		 * when it tries to use the FP unit.  Restore the
 		 * state here
 		 */
-		if (npxdna())
+		if (npxdna(frame))
 			goto out;
 #endif
 		if (!pmath_emulate) {
@@ -677,7 +694,8 @@ kernel_trap:
 		 * The kernel may be using npx for copying or other
 		 * purposes.
 		 */
-		if (npxdna())
+		panic("kernel NPX should not happen");
+		if (npxdna(frame))
 			goto out2;
 #endif
 		break;
@@ -1391,6 +1409,20 @@ go_user(struct trapframe frame)
 			&curproc->p_vmspace->vm_pmap,
 			curproc->p_pid, curproc->p_comm, sigblock(0));
 #endif
+
+		/*
+		 * Tell the real kernel whether it is ok to use the FP
+		 * unit or not.
+		 */
+		if (mdcpu->gd_npxthread == curthread) {
+			frame.tf_xflags &= ~FPEX_FAULT;
+		} else {
+			frame.tf_xflags |= FPEX_FAULT;
+		}
+
+		/*
+		 * Run emulated user process context
+		 */
 		r = vmspace_ctl(&curproc->p_vmspace->vm_pmap, VMSPACE_CTL_RUN,
 				&frame, &curthread->td_savevext);
 		if (r < 0)
@@ -1415,3 +1447,25 @@ go_user(struct trapframe frame)
 	}
 }
 
+/*
+ * If FPEX_FAULT is set then set FP_VIRTFP in the PCB to force a T_DNA
+ * fault (which is then passed back to the virtual kernel) if an attempt is
+ * made to use the FP unit.
+ * 
+ * XXX this is a fairly big hack.
+ */
+void
+set_vkernel_fp(struct trapframe *frame)
+{
+	struct thread *td = curthread;
+
+	panic("set_vkernel_fp: vkernel-within-vkernel not yet supported");
+	if (frame->tf_xflags & FPEX_FAULT) {
+		td->td_pcb->pcb_flags |= FP_VIRTFP;
+		if (mdcpu->gd_npxthread == td)
+			npxexit();
+	} else {
+		td->td_pcb->pcb_flags &= ~FP_VIRTFP;
+	}
+}
+
diff --git a/sys/platform/vkernel/i386/vm_machdep.c b/sys/platform/vkernel/i386/vm_machdep.c
index 1e2a08abe0..977a3ec2d4 100644
--- a/sys/platform/vkernel/i386/vm_machdep.c
+++ b/sys/platform/vkernel/i386/vm_machdep.c
@@ -39,7 +39,7 @@
  *	from: @(#)vm_machdep.c	7.3 (Berkeley) 5/13/91
  *	Utah $Hdr: vm_machdep.c 1.16.1.1 89/06/23$
  * $FreeBSD: src/sys/i386/i386/vm_machdep.c,v 1.132.2.9 2003/01/25 19:02:23 dillon Exp $
- * $DragonFly: src/sys/platform/vkernel/i386/vm_machdep.c,v 1.3 2007/01/08 03:33:43 dillon Exp $
+ * $DragonFly: src/sys/platform/vkernel/i386/vm_machdep.c,v 1.4 2007/01/09 23:34:05 dillon Exp $
  */
 
 #include "use_npx.h"
@@ -156,7 +156,7 @@ cpu_fork(struct lwp *lp1, struct lwp *lp2, int flags)
 	 * Set registers for trampoline to user mode.  Leave space for the
 	 * return address on stack.  These are the kernel mode register values.
 	 */
-	pcb2->pcb_cr3 = vtophys(vmspace_pmap(lp2->lwp_proc->p_vmspace)->pm_pdir);
+	pcb2->pcb_unused01 = 0;
 	pcb2->pcb_edi = 0;
 	pcb2->pcb_esi = (int)fork_return;	/* fork_trampoline argument */
 	pcb2->pcb_ebp = 0;
diff --git a/sys/platform/vkernel/include/md_var.h b/sys/platform/vkernel/include/md_var.h
index 36721c61a3..d4637ce9b7 100644
--- a/sys/platform/vkernel/include/md_var.h
+++ b/sys/platform/vkernel/include/md_var.h
@@ -31,7 +31,7 @@
  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  * 
- * $DragonFly: src/sys/platform/vkernel/include/md_var.h,v 1.10 2007/01/09 00:20:19 dillon Exp $
+ * $DragonFly: src/sys/platform/vkernel/include/md_var.h,v 1.11 2007/01/09 23:34:05 dillon Exp $
  */
 
 #ifndef _MACHINE_MD_VAR_H_
@@ -77,6 +77,7 @@ void kern_trap(struct trapframe *);
 void user_trap(struct trapframe *);
 void syscall2 (struct trapframe *);
 void vcons_set_mode(int);
+int npxdna(struct trapframe *);
 
 #endif
 
diff --git a/sys/platform/vkernel/include/pcb.h b/sys/platform/vkernel/include/pcb.h
index d4939a2f37..48e64a56f4 100644
--- a/sys/platform/vkernel/include/pcb.h
+++ b/sys/platform/vkernel/include/pcb.h
@@ -35,7 +35,7 @@
  *
  *	from: @(#)pcb.h	5.10 (Berkeley) 5/12/91
  * $FreeBSD: src/sys/i386/include/pcb.h,v 1.32.2.1 2001/08/15 01:23:52 peter Exp $
- * $DragonFly: src/sys/platform/vkernel/include/pcb.h,v 1.2 2007/01/08 03:33:43 dillon Exp $
+ * $DragonFly: src/sys/platform/vkernel/include/pcb.h,v 1.3 2007/01/09 23:34:05 dillon Exp $
  */
 
 #ifndef _MACHINE_PCB_H_
@@ -47,7 +47,7 @@
 #include <machine/npx.h>
 
 struct pcb {
-	int	pcb_cr3;
+	int	pcb_unused01;
 	int	pcb_edi;
 	int	pcb_esi;
 	int	pcb_ebp;
@@ -67,6 +67,7 @@ struct pcb {
 	u_char	pcb_flags;
 #define	FP_SOFTFP	0x01	/* process using software fltng pnt emulator */
 #define	PCB_DBREGS	0x02	/* process using debug registers */
+#define FP_VIRTFP	0x04	/* virtual kernel wants exception */
 	caddr_t	pcb_onfault;	/* copyin/out fault recovery */
 	int	pcb_unused;
 	struct	pcb_ext	*pcb_ext;	/* optional pcb extension */
diff --git a/sys/sys/systm.h b/sys/sys/systm.h
index 59d4738047..337861ed0f 100644
--- a/sys/sys/systm.h
+++ b/sys/sys/systm.h
@@ -37,7 +37,7 @@
  *
  *	@(#)systm.h	8.7 (Berkeley) 3/29/95
  * $FreeBSD: src/sys/sys/systm.h,v 1.111.2.18 2002/12/17 18:04:02 sam Exp $
- * $DragonFly: src/sys/sys/systm.h,v 1.60 2007/01/08 03:33:43 dillon Exp $
+ * $DragonFly: src/sys/sys/systm.h,v 1.61 2007/01/09 23:34:05 dillon Exp $
  */
 
 #ifndef _SYS_SYSTM_H_
@@ -148,6 +148,7 @@ void	cpu_rootconf (void);
 void	cpu_vmspace_alloc(struct vmspace *);
 void	cpu_vmspace_free(struct vmspace *);
 void	set_user_TLS(void);
+void	set_vkernel_fp(struct trapframe *);
 
 vm_paddr_t kvtop(void *addr);
 int	is_physical_memory (vm_offset_t addr);
diff --git a/sys/vm/vm_vmspace.c b/sys/vm/vm_vmspace.c
index b89f03a2ec..acd321c3c1 100644
--- a/sys/vm/vm_vmspace.c
+++ b/sys/vm/vm_vmspace.c
@@ -31,7 +31,7 @@
  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  * 
- * $DragonFly: src/sys/vm/vm_vmspace.c,v 1.8 2007/01/08 03:33:43 dillon Exp $
+ * $DragonFly: src/sys/vm/vm_vmspace.c,v 1.9 2007/01/09 23:34:06 dillon Exp $
  */
 #include "opt_ddb.h"
 
@@ -194,6 +194,7 @@ sys_vmspace_ctl(struct vmspace_ctl_args *uap)
 			p->p_vmspace = ve->vmspace;
 			pmap_activate(p);
 			set_user_TLS();
+			set_vkernel_fp(uap->sysmsg_frame);
 			error = EJUSTRETURN;
 		}
 		break;
-- 
2.41.0