o) Add a VM find-space option, VMFS_TLB_ALIGNED_SPACE, which searches the

   address space for an address as aligned by the new pmap_align_tlb()
   function, which is for constraints imposed by the TLB. [1]
o) Add a kmem_alloc_nofault_space() function, which acts like
   kmem_alloc_nofault() but allows the caller to specify which find-space
   option to use. [1]
o) Use kmem_alloc_nofault_space() with VMFS_TLB_ALIGNED_SPACE to allocate the
   kernel stack address on MIPS. [1]
o) Make pmap_align_tlb() on MIPS align addresses so that they do not start on
   an odd boundary within the TLB, so that they are suitable for insertion as
   wired entries and do not have to share a TLB entry with another mapping,
   assuming they are appropriately-sized.
o) Eliminate md_realstack now that the kstack will be appropriately-aligned on
   MIPS.
o) Increase the number of guard pages to 2 so that we retain the proper
   alignment of the kstack address.

Reviewed by:	[1] alc
X-MFC-after:	Making sure alc has not come up with a better interface.

8 files changed, 31 insertions, 33 deletions

diff --git a/sys/mips/include/param.h b/sys/mips/include/param.h
index 0edb8b9..06cdeac 100644
--- a/sys/mips/include/param.h
+++ b/sys/mips/include/param.h
@@ -113,12 +113,9 @@
 
 /*
  * The kernel stack needs to be aligned on a (PAGE_SIZE * 2) boundary.
- *
- * Although we allocate 3 pages for the kernel stack we end up using
- * only the 2 pages that are aligned on a (PAGE_SIZE * 2) boundary.
  */
-#define	KSTACK_PAGES		3	/* kernel stack*/
-#define	KSTACK_GUARD_PAGES	1	/* pages of kstack guard; 0 disables */
+#define	KSTACK_PAGES		2	/* kernel stack*/
+#define	KSTACK_GUARD_PAGES	2	/* pages of kstack guard; 0 disables */
 
 #define	UPAGES			2
 
diff --git a/sys/mips/include/proc.h b/sys/mips/include/proc.h
index 99dab78..0491b11 100644
--- a/sys/mips/include/proc.h
+++ b/sys/mips/include/proc.h
@@ -44,7 +44,7 @@
  */
 struct mdthread {
 	int	md_flags;		/* machine-dependent flags */
-	int	md_upte[KSTACK_PAGES - 1]; /* ptes for mapping u pcb */
+	int	md_upte[KSTACK_PAGES];	/* ptes for mapping u pcb */
 	int	md_ss_addr;		/* single step address for ptrace */
 	int	md_ss_instr;		/* single step instruction for ptrace */
 	register_t	md_saved_intr;
@@ -53,7 +53,6 @@ struct mdthread {
 	int	md_pc_ctrl;		/* performance counter control */
 	int	md_pc_count;		/* performance counter */
 	int	md_pc_spill;		/* performance counter spill */
-	vm_offset_t	md_realstack;
 	void	*md_tls;
 };
 
diff --git a/sys/mips/mips/exception.S b/sys/mips/mips/exception.S
index 8c32b58..aa775ea 100644
--- a/sys/mips/mips/exception.S
+++ b/sys/mips/mips/exception.S
@@ -928,7 +928,7 @@ tlb_insert_random:
 	 */
 	GET_CPU_PCPU(k1)
 	lw	k0, PC_CURTHREAD(k1)
-	lw	k0, TD_REALKSTACK(k0)
+	lw	k0, TD_KSTACK(k0)
 	sltu	k0, k0, sp
 	bnez	k0, _C_LABEL(MipsKernGenException)
 	nop
@@ -975,7 +975,7 @@ tlb_insert_random:
 	 */
 	GET_CPU_PCPU(k1)
 	lw	k0, PC_CURTHREAD(k1)
-	sw	zero, TD_REALKSTACK(k0)
+	sw	zero, TD_KSTACK(k0)
 
 	move	a1, a0
 	PANIC("kernel stack overflow - trapframe at %p")
diff --git a/sys/mips/mips/genassym.c b/sys/mips/mips/genassym.c
index 6cec2b7..b10a5e2 100644
--- a/sys/mips/mips/genassym.c
+++ b/sys/mips/mips/genassym.c
@@ -65,7 +65,7 @@ __FBSDID("$FreeBSD$");
 
 ASSYM(TD_PCB, offsetof(struct thread, td_pcb));
 ASSYM(TD_UPTE, offsetof(struct thread, td_md.md_upte));
-ASSYM(TD_REALKSTACK, offsetof(struct thread, td_md.md_realstack));
+ASSYM(TD_KSTACK, offsetof(struct thread, td_kstack));
 ASSYM(TD_FLAGS, offsetof(struct thread, td_flags));
 ASSYM(TD_LOCK, offsetof(struct thread, td_lock));
 ASSYM(TD_FRAME, offsetof(struct thread, td_frame));
diff --git a/sys/mips/mips/machdep.c b/sys/mips/mips/machdep.c
index 6ca4ec9..b3f36e5 100644
--- a/sys/mips/mips/machdep.c
+++ b/sys/mips/mips/machdep.c
@@ -298,14 +298,13 @@ mips_proc0_init(void)
 		(long)kstack0));
 	thread0.td_kstack = kstack0;
 	thread0.td_kstack_pages = KSTACK_PAGES;
-	thread0.td_md.md_realstack = roundup2(thread0.td_kstack, PAGE_SIZE * 2);
 	/* 
 	 * Do not use cpu_thread_alloc to initialize these fields 
 	 * thread0 is the only thread that has kstack located in KSEG0 
 	 * while cpu_thread_alloc handles kstack allocated in KSEG2.
 	 */
-	thread0.td_pcb = (struct pcb *)(thread0.td_md.md_realstack +
-	    (thread0.td_kstack_pages - 1) * PAGE_SIZE) - 1;
+	thread0.td_pcb = (struct pcb *)(thread0.td_kstack +
+	    thread0.td_kstack_pages * PAGE_SIZE) - 1;
 	thread0.td_frame = &thread0.td_pcb->pcb_regs;
 
 	/* Steal memory for the dynamic per-cpu area. */
diff --git a/sys/mips/mips/pmap.c b/sys/mips/mips/pmap.c
index 6bb38d4..e3b7daf 100644
--- a/sys/mips/mips/pmap.c
+++ b/sys/mips/mips/pmap.c
@@ -2813,6 +2813,21 @@ pmap_align_superpage(vm_object_t object, vm_ooffset_t offset,
 		*addr = ((*addr + SEGOFSET) & ~SEGOFSET) + superpage_offset;
 }
 
+/*
+ * 	Increase the starting virtual address of the given mapping so
+ * 	that it is aligned to not be the second page in a TLB entry.
+ * 	This routine assumes that the length is appropriately-sized so
+ * 	that the allocation does not share a TLB entry at all if required.
+ */
+void
+pmap_align_tlb(vm_offset_t *addr)
+{
+	if ((*addr & PAGE_SIZE) == 0)
+		return;
+	*addr += PAGE_SIZE;
+	return;
+}
+
 int pmap_pid_dump(int pid);
 
 int
diff --git a/sys/mips/mips/swtch.S b/sys/mips/mips/swtch.S
index 4fc3cbd..2919d21 100644
--- a/sys/mips/mips/swtch.S
+++ b/sys/mips/mips/swtch.S
@@ -339,7 +339,7 @@ blocked_loop:
 	sw	a1, PC_CURTHREAD(a3)
 	lw	a2, TD_PCB(a1)
 	sw	a2, PC_CURPCB(a3)
-	lw	v0, TD_REALKSTACK(a1)
+	lw	v0, TD_KSTACK(a1)
 	li	s0, MIPS_KSEG2_START		# If Uarea addr is below kseg2,
 	bltu	v0, s0, sw2			# no need to insert in TLB.
 	lw	a1, TD_UPTE+0(s7)		# t0 = first u. pte
diff --git a/sys/mips/mips/vm_machdep.c b/sys/mips/mips/vm_machdep.c
index cb8a8d9..d385fdd 100644
--- a/sys/mips/mips/vm_machdep.c
+++ b/sys/mips/mips/vm_machdep.c
@@ -217,13 +217,9 @@ cpu_thread_swapin(struct thread *td)
 	 * part of the thread struct so cpu_switch() can quickly map in
 	 * the pcb struct and kernel stack.
 	 */
-	if (!(pte = pmap_segmap(kernel_pmap, td->td_md.md_realstack)))
-		panic("cpu_thread_swapin: invalid segmap");
-	pte += ((vm_offset_t)td->td_md.md_realstack >> PAGE_SHIFT) & (NPTEPG - 1);
-
-	for (i = 0; i < KSTACK_PAGES - 1; i++) {
+	for (i = 0; i < KSTACK_PAGES; i++) {
+		pte = pmap_pte(kernel_pmap, td->td_kstack + i * PAGE_SIZE);
 		td->td_md.md_upte[i] = *pte & ~(PTE_RO|PTE_WIRED);
-		pte++;
 	}
 }
 
@@ -238,22 +234,14 @@ cpu_thread_alloc(struct thread *td)
 	pt_entry_t *pte;
 	int i;
 
-	if (td->td_kstack & (1 << PAGE_SHIFT))
-		td->td_md.md_realstack = td->td_kstack + PAGE_SIZE;
-	else
-		td->td_md.md_realstack = td->td_kstack;
-
-	td->td_pcb = (struct pcb *)(td->td_md.md_realstack +
-	    (td->td_kstack_pages - 1) * PAGE_SIZE) - 1;
+	KASSERT((td->td_kstack & (1 << PAGE_SHIFT)) == 0, ("kernel stack must be aligned."));
+	td->td_pcb = (struct pcb *)(td->td_kstack +
+	    td->td_kstack_pages * PAGE_SIZE) - 1;
 	td->td_frame = &td->td_pcb->pcb_regs;
 
-	if (!(pte = pmap_segmap(kernel_pmap, td->td_md.md_realstack)))
-		panic("cpu_thread_alloc: invalid segmap");
-	pte += ((vm_offset_t)td->td_md.md_realstack >> PAGE_SHIFT) & (NPTEPG - 1);
-
-	for (i = 0; i < KSTACK_PAGES - 1; i++) {
+	for (i = 0; i < KSTACK_PAGES; i++) {
+		pte = pmap_pte(kernel_pmap, td->td_kstack + i * PAGE_SIZE);
 		td->td_md.md_upte[i] = *pte & ~(PTE_RO|PTE_WIRED);
-		pte++;
 	}
 }