diff --git a/sys/alpha/alpha/pmap.c b/sys/alpha/alpha/pmap.c
index 94cf81b74fe..082388591b5 100644
--- a/sys/alpha/alpha/pmap.c
+++ b/sys/alpha/alpha/pmap.c
@@ -1063,35 +1063,6 @@ pmap_dispose_thread(td)
 	vm_object_deallocate(ksobj);
 }
 
-/*
- * Set up a variable sized alternate kstack.
- */
-void
-pmap_new_altkstack(struct thread *td, int pages)
-{
-	/* shuffle the original stack */
-	td->td_altkstack_obj = td->td_kstack_obj;
-	td->td_altkstack = td->td_kstack;
-	td->td_altkstack_pages = td->td_kstack_pages;
-
-	pmap_new_thread(td, pages);
-}
-
-void
-pmap_dispose_altkstack(td)
-	struct thread *td;
-{
-	pmap_dispose_thread(td);
-
-	/* restore the original kstack */
-	td->td_kstack = td->td_altkstack;
-	td->td_kstack_obj = td->td_altkstack_obj;
-	td->td_kstack_pages = td->td_altkstack_pages;
-	td->td_altkstack = 0;
-	td->td_altkstack_obj = NULL;
-	td->td_altkstack_pages = 0;
-}
-
 /*
  * Allow the kernel stack for a thread to be prejudicially paged out.
  */
diff --git a/sys/amd64/amd64/pmap.c b/sys/amd64/amd64/pmap.c
index d3cdb59f893..38a5f5b3658 100644
--- a/sys/amd64/amd64/pmap.c
+++ b/sys/amd64/amd64/pmap.c
@@ -996,36 +996,6 @@ pmap_dispose_thread(td)
 	vm_object_deallocate(ksobj);
 }
 
-/*
- * Set up a variable sized alternate kstack.  Though it may look MI, it may
- * need to be different on certain arches like ia64.
- */
-void
-pmap_new_altkstack(struct thread *td, int pages)
-{
-	/* shuffle the original stack */
-	td->td_altkstack_obj = td->td_kstack_obj;
-	td->td_altkstack = td->td_kstack;
-	td->td_altkstack_pages = td->td_kstack_pages;
-
-	pmap_new_thread(td, pages);
-}
-
-void
-pmap_dispose_altkstack(td)
-	struct thread *td;
-{
-	pmap_dispose_thread(td);
-
-	/* restore the original kstack */
-	td->td_kstack = td->td_altkstack;
-	td->td_kstack_obj = td->td_altkstack_obj;
-	td->td_kstack_pages = td->td_altkstack_pages;
-	td->td_altkstack = 0;
-	td->td_altkstack_obj = NULL;
-	td->td_altkstack_pages = 0;
-}
-
 /*
  * Allow the Kernel stack for a thread to be prejudicially paged out.
  */
diff --git a/sys/i386/i386/pmap.c b/sys/i386/i386/pmap.c
index c9135707753..c9a910ea67a 100644
--- a/sys/i386/i386/pmap.c
+++ b/sys/i386/i386/pmap.c
@@ -1099,36 +1099,6 @@ pmap_dispose_thread(td)
 	vm_object_deallocate(ksobj);
 }
 
-/*
- * Set up a variable sized alternate kstack.  Though it may look MI, it may
- * need to be different on certain arches like ia64.
- */
-void
-pmap_new_altkstack(struct thread *td, int pages)
-{
-	/* shuffle the original stack */
-	td->td_altkstack_obj = td->td_kstack_obj;
-	td->td_altkstack = td->td_kstack;
-	td->td_altkstack_pages = td->td_kstack_pages;
-
-	pmap_new_thread(td, pages);
-}
-
-void
-pmap_dispose_altkstack(td)
-	struct thread *td;
-{
-	pmap_dispose_thread(td);
-
-	/* restore the original kstack */
-	td->td_kstack = td->td_altkstack;
-	td->td_kstack_obj = td->td_altkstack_obj;
-	td->td_kstack_pages = td->td_altkstack_pages;
-	td->td_altkstack = 0;
-	td->td_altkstack_obj = NULL;
-	td->td_altkstack_pages = 0;
-}
-
 /*
  * Allow the Kernel stack for a thread to be prejudicially paged out.
  */
diff --git a/sys/ia64/ia64/pmap.c b/sys/ia64/ia64/pmap.c
index 2e9d472d9ed..dd6ba1df2f7 100644
--- a/sys/ia64/ia64/pmap.c
+++ b/sys/ia64/ia64/pmap.c
@@ -796,32 +796,6 @@ pmap_dispose_thread(struct thread *td)
 	td->td_kstack_pages = 0;
 }
 
-/*
- * Set up a variable sized alternate kstack.  This appears to be MI.
- */
-void
-pmap_new_altkstack(struct thread *td, int pages)
-{
-
-	td->td_altkstack = td->td_kstack;
-	td->td_altkstack_obj = td->td_kstack_obj;
-	td->td_altkstack_pages = td->td_kstack_pages;
-	pmap_new_thread(td, pages);
-}
-
-void
-pmap_dispose_altkstack(struct thread *td)
-{
-
-	pmap_dispose_thread(td);
-	td->td_kstack = td->td_altkstack;
-	td->td_kstack_obj = td->td_altkstack_obj;
-	td->td_kstack_pages = td->td_altkstack_pages;
-	td->td_altkstack = 0;
-	td->td_altkstack_obj = NULL;
-	td->td_altkstack_pages = 0;
-}
-
 /*
  * Allow the KSTACK for a thread to be prejudicially paged out.
  */
diff --git a/sys/kern/kern_fork.c b/sys/kern/kern_fork.c
index e9e38ab3025..4c514dfadc7 100644
--- a/sys/kern/kern_fork.c
+++ b/sys/kern/kern_fork.c
@@ -460,7 +460,7 @@ again:
 
 	/* Allocate and switch to an alternate kstack if specified */
 	if (pages != 0)
-		pmap_new_altkstack(td2, pages);
+		vm_thread_new_altkstack(td2, pages);
 
 	PROC_LOCK(p2);
 	PROC_LOCK(p1);
diff --git a/sys/kern/kern_proc.c b/sys/kern/kern_proc.c
index 548f0976fce..c798b682815 100644
--- a/sys/kern/kern_proc.c
+++ b/sys/kern/kern_proc.c
@@ -168,7 +168,7 @@ proc_dtor(void *mem, int size, void *arg)
 	 *     freed, so you gotta do this here.
 	 */
 	if (((p->p_flag & P_KTHREAD) != 0) && (td->td_altkstack != 0))
-		pmap_dispose_altkstack(td);
+		vm_thread_dispose_altkstack(td);
 
 	/*
 	 * We want to make sure we know the initial linkages.
diff --git a/sys/powerpc/aim/mmu_oea.c b/sys/powerpc/aim/mmu_oea.c
index 00528814ac5..4808b4ddd8d 100644
--- a/sys/powerpc/aim/mmu_oea.c
+++ b/sys/powerpc/aim/mmu_oea.c
@@ -1652,31 +1652,6 @@ pmap_dispose_thread(struct thread *td)
 	vm_object_deallocate(ksobj);
 }
 
-void
-pmap_new_altkstack(struct thread *td, int pages)
-{
-	/* shuffle the original stack */
-	td->td_altkstack_obj = td->td_kstack_obj;
-	td->td_altkstack = td->td_kstack;
-	td->td_altkstack_pages = td->td_kstack_pages;
-
-	pmap_new_thread(td, pages);
-}
-
-void
-pmap_dispose_altkstack(struct thread *td)
-{
-	pmap_dispose_thread(td);
-
-	/* restore the original kstack */
-	td->td_kstack = td->td_altkstack;
-	td->td_kstack_obj = td->td_altkstack_obj;
-	td->td_kstack_pages = td->td_altkstack_pages;
-	td->td_altkstack = 0;
-	td->td_altkstack_obj = NULL;
-	td->td_altkstack_pages = 0;
-}
-
 void
 pmap_swapin_thread(struct thread *td)
 {
diff --git a/sys/powerpc/powerpc/mmu_oea.c b/sys/powerpc/powerpc/mmu_oea.c
index 00528814ac5..4808b4ddd8d 100644
--- a/sys/powerpc/powerpc/mmu_oea.c
+++ b/sys/powerpc/powerpc/mmu_oea.c
@@ -1652,31 +1652,6 @@ pmap_dispose_thread(struct thread *td)
 	vm_object_deallocate(ksobj);
 }
 
-void
-pmap_new_altkstack(struct thread *td, int pages)
-{
-	/* shuffle the original stack */
-	td->td_altkstack_obj = td->td_kstack_obj;
-	td->td_altkstack = td->td_kstack;
-	td->td_altkstack_pages = td->td_kstack_pages;
-
-	pmap_new_thread(td, pages);
-}
-
-void
-pmap_dispose_altkstack(struct thread *td)
-{
-	pmap_dispose_thread(td);
-
-	/* restore the original kstack */
-	td->td_kstack = td->td_altkstack;
-	td->td_kstack_obj = td->td_altkstack_obj;
-	td->td_kstack_pages = td->td_altkstack_pages;
-	td->td_altkstack = 0;
-	td->td_altkstack_obj = NULL;
-	td->td_altkstack_pages = 0;
-}
-
 void
 pmap_swapin_thread(struct thread *td)
 {
diff --git a/sys/powerpc/powerpc/pmap.c b/sys/powerpc/powerpc/pmap.c
index 00528814ac5..4808b4ddd8d 100644
--- a/sys/powerpc/powerpc/pmap.c
+++ b/sys/powerpc/powerpc/pmap.c
@@ -1652,31 +1652,6 @@ pmap_dispose_thread(struct thread *td)
 	vm_object_deallocate(ksobj);
 }
 
-void
-pmap_new_altkstack(struct thread *td, int pages)
-{
-	/* shuffle the original stack */
-	td->td_altkstack_obj = td->td_kstack_obj;
-	td->td_altkstack = td->td_kstack;
-	td->td_altkstack_pages = td->td_kstack_pages;
-
-	pmap_new_thread(td, pages);
-}
-
-void
-pmap_dispose_altkstack(struct thread *td)
-{
-	pmap_dispose_thread(td);
-
-	/* restore the original kstack */
-	td->td_kstack = td->td_altkstack;
-	td->td_kstack_obj = td->td_altkstack_obj;
-	td->td_kstack_pages = td->td_altkstack_pages;
-	td->td_altkstack = 0;
-	td->td_altkstack_obj = NULL;
-	td->td_altkstack_pages = 0;
-}
-
 void
 pmap_swapin_thread(struct thread *td)
 {
diff --git a/sys/sparc64/sparc64/pmap.c b/sys/sparc64/sparc64/pmap.c
index c58d4b4c6da..4e308591107 100644
--- a/sys/sparc64/sparc64/pmap.c
+++ b/sys/sparc64/sparc64/pmap.c
@@ -1030,34 +1030,6 @@ pmap_dispose_thread(struct thread *td)
 	vm_object_deallocate(ksobj);
 }
 
-/*
- * Set up a variable sized alternate kstack.
- */
-void
-pmap_new_altkstack(struct thread *td, int pages)
-{
-	/* shuffle the original stack */
-	td->td_altkstack_obj = td->td_kstack_obj;
-	td->td_altkstack = td->td_kstack;
-	td->td_altkstack_pages = td->td_kstack_pages;
-
-	pmap_new_thread(td, pages);
-}
-
-void
-pmap_dispose_altkstack(struct thread *td)
-{
-	pmap_dispose_thread(td);
-
-	/* restore the original kstack */
-	td->td_kstack = td->td_altkstack;
-	td->td_kstack_obj = td->td_altkstack_obj;
-	td->td_kstack_pages = td->td_altkstack_pages;
-	td->td_altkstack = 0;
-	td->td_altkstack_obj = NULL;
-	td->td_altkstack_pages = 0;
-}
-
 /*
  * Allow the kernel stack for a thread to be prejudicially paged out.
  */
diff --git a/sys/vm/pmap.h b/sys/vm/pmap.h
index 1a1e232059f..36ca187387f 100644
--- a/sys/vm/pmap.h
+++ b/sys/vm/pmap.h
@@ -131,8 +131,6 @@ void		 pmap_prefault(pmap_t, vm_offset_t, vm_map_entry_t);
 int		 pmap_mincore(pmap_t pmap, vm_offset_t addr);
 void		 pmap_new_thread(struct thread *td, int pages);
 void		 pmap_dispose_thread(struct thread *td);
-void		 pmap_new_altkstack(struct thread *td, int pages);
-void		 pmap_dispose_altkstack(struct thread *td);
 void		 pmap_swapout_thread(struct thread *td);
 void		 pmap_swapin_thread(struct thread *td);
 void		 pmap_activate(struct thread *td);
diff --git a/sys/vm/vm_extern.h b/sys/vm/vm_extern.h
index eafc30075e8..4718effac50 100644
--- a/sys/vm/vm_extern.h
+++ b/sys/vm/vm_extern.h
@@ -96,5 +96,7 @@ void vm_object_print(/* db_expr_t */ long, boolean_t, /* db_expr_t */ long,
 int vm_fault_quick(caddr_t v, int prot);
 void vm_proc_new(struct proc *p);
 void vm_proc_dispose(struct proc *p);
+void vm_thread_new_altkstack(struct thread *td, int pages);
+void vm_thread_dispose_altkstack(struct thread *td);
 #endif				/* _KERNEL */
 #endif				/* !_VM_EXTERN_H_ */
diff --git a/sys/vm/vm_glue.c b/sys/vm/vm_glue.c
index ec15d968cd0..2145c0c2f72 100644
--- a/sys/vm/vm_glue.c
+++ b/sys/vm/vm_glue.c
@@ -387,6 +387,37 @@ retry:
 }
 #endif
 
+/*
+ * Set up a variable-sized alternate kstack.
+ */
+void
+vm_thread_new_altkstack(struct thread *td, int pages)
+{
+
+	td->td_altkstack = td->td_kstack;
+	td->td_altkstack_obj = td->td_kstack_obj;
+	td->td_altkstack_pages = td->td_kstack_pages;
+
+	pmap_new_thread(td, pages);
+}
+
+/*
+ * Restore the original kstack.
+ */
+void
+vm_thread_dispose_altkstack(struct thread *td)
+{
+
+	pmap_dispose_thread(td);
+
+	td->td_kstack = td->td_altkstack;
+	td->td_kstack_obj = td->td_altkstack_obj;
+	td->td_kstack_pages = td->td_altkstack_pages;
+	td->td_altkstack = 0;
+	td->td_altkstack_obj = NULL;
+	td->td_altkstack_pages = 0;
+}
+
 /*
  * Implement fork's actions on an address space.
  * Here we arrange for the address space to be copied or referenced,