Index: include/fpu.h
===================================================================
RCS file: /cvsroot/src/sys/arch/powerpc/include/fpu.h,v
retrieving revision 1.19
diff -p -u -r1.19 fpu.h
--- include/fpu.h	19 May 2011 08:22:38 -0000	1.19
+++ include/fpu.h	13 Jun 2011 00:05:39 -0000
@@ -77,6 +77,7 @@
 #include <powerpc/mcontext.h>
 
 struct lwp;
+bool	fpu_dirty_p(struct lwp *);
 bool	fpu_used_p(struct lwp *);
 void	fpu_mark_used(struct lwp *);
 
Index: include/proc.h
===================================================================
RCS file: /cvsroot/src/sys/arch/powerpc/include/proc.h,v
retrieving revision 1.12
diff -p -u -r1.12 proc.h
--- include/proc.h	5 Jun 2011 16:52:25 -0000	1.12
+++ include/proc.h	13 Jun 2011 00:05:39 -0000
@@ -44,6 +44,7 @@ struct mdlwp {
 };
 #define MDLWP_USEDFPU	__BIT(PCU_FPU)	/* this thread has used the FPU */
 #define	MDLWP_USEDVEC	__BIT(PCU_VEC)	/* this thread has used the VEC */
+#define	MDLWP_DIRTYFPU	__BIT(4)	/* XXX thread is dirty on fpu */
 
 struct trapframe;
 
Index: powerpc/fpu.c
===================================================================
RCS file: /cvsroot/src/sys/arch/powerpc/powerpc/fpu.c,v
retrieving revision 1.31
diff -p -u -r1.31 fpu.c
--- powerpc/fpu.c	7 Jun 2011 01:01:43 -0000	1.31
+++ powerpc/fpu.c	13 Jun 2011 00:05:39 -0000
@@ -63,6 +63,12 @@ const pcu_ops_t fpu_ops = {
 };
 
 bool
+fpu_dirty_p(lwp_t *l)
+{
+	return (l->l_md.md_flags & MDLWP_DIRTYFPU) != 0;
+}
+
+bool
 fpu_used_p(lwp_t *l)
 {
 	return (l->l_md.md_flags & MDLWP_USEDFPU) != 0;
@@ -97,7 +103,7 @@ fpu_state_load(lwp_t *l, bool used)
 
 	curcpu()->ci_ev_fpusw.ev_count++;
 	l->l_md.md_utf->tf_srr1 |= PSL_FP|(pcb->pcb_flags & (PCB_FE0|PCB_FE1));
-	l->l_md.md_flags |= MDLWP_USEDFPU;
+	l->l_md.md_flags |= MDLWP_USEDFPU | MDLWP_DIRTYFPU;
 }
 
 /*
@@ -117,12 +123,15 @@ fpu_state_save(lwp_t *l)
 
 	mtmsr(msr);
 	__asm volatile ("isync");
+
+	l->l_md.md_flags &= ~MDLWP_DIRTYFPU;
 }
 
 void
 fpu_state_release(lwp_t *l)
 {
 	l->l_md.md_utf->tf_srr1 &= ~PSL_FP;
+	l->l_md.md_flags &= ~MDLWP_DIRTYFPU;
 }
 
 #define	STICKYBITS	(FPSCR_VX|FPSCR_OX|FPSCR_UX|FPSCR_ZX|FPSCR_XX)
Index: powerpc/process_machdep.c
===================================================================
RCS file: /cvsroot/src/sys/arch/powerpc/powerpc/process_machdep.c,v
retrieving revision 1.32
diff -p -u -r1.32 process_machdep.c
--- powerpc/process_machdep.c	12 Jun 2011 20:38:10 -0000	1.32
+++ powerpc/process_machdep.c	13 Jun 2011 00:05:39 -0000
@@ -89,9 +89,11 @@ process_read_fpregs(struct lwp *l, struc
 		memset(fpregs, 0, sizeof (*fpregs));
 #ifdef PPC_HAVE_FPU
 	} else {
-		KASSERTMSG(l == curlwp,
-		    ("%s: l (%p) != curlwp (%p)", __func__, l, curlwp));
-		fpu_save();
+		if (fpu_dirty_p(l)) {
+			KASSERTMSG(l == curlwp,
+			    ("%s: l (%p) != curlwp (%p)", __func__, l, curlwp));
+			fpu_save();
+		}
 #endif
 	}
 	*fpregs = pcb->pcb_fpu;