powerpc/64s/hash: Simplify slb_flush_and_rebolt()

slb_flush_and_rebolt() is misleading, it is called in virtual mode, so
it can not possibly change the stack, so it should not be touching the
shadow area. And since vmalloc is no longer bolted, it should not
change any bolted mappings at all.

Change the name to slb_flush_and_restore_bolted(), and have it just
load the kernel stack from what's currently in the shadow SLB area.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

1 files changed, 16 insertions, 30 deletions

diff --git a/arch/powerpc/mm/slb.c b/arch/powerpc/mm/slb.c
index 3b7d8af09724..d8d9c9bd15d3 100644
--- a/arch/powerpc/mm/slb.c
+++ b/arch/powerpc/mm/slb.c
@@ -115,8 +115,6 @@ void __slb_restore_bolted_realmode(void)
 
 /*
  * Insert the bolted entries into an empty SLB.
- * This is not the same as rebolt because the bolted segments are not
- * changed, just loaded from the shadow area.
  */
 void slb_restore_bolted_realmode(void)
 {
@@ -135,12 +133,15 @@ void slb_flush_all_realmode(void)
 	asm volatile("slbmte %0,%0; slbia" : : "r" (0));
 }
 
-void slb_flush_and_rebolt(void)
+/*
+ * This flushes non-bolted entries, it can be run in virtual mode. Must
+ * be called with interrupts disabled.
+ */
+void slb_flush_and_restore_bolted(void)
 {
-	/* If you change this make sure you change SLB_NUM_BOLTED
-	 * and PR KVM appropriately too. */
-	unsigned long linear_llp, lflags;
-	unsigned long ksp_esid_data, ksp_vsid_data;
+	struct slb_shadow *p = get_slb_shadow();
+
+	BUILD_BUG_ON(SLB_NUM_BOLTED != 2);
 
 	WARN_ON(!irqs_disabled());
 
@@ -150,30 +151,12 @@ void slb_flush_and_rebolt(void)
 	 */
 	hard_irq_disable();
 
-	linear_llp = mmu_psize_defs[mmu_linear_psize].sllp;
-	lflags = SLB_VSID_KERNEL | linear_llp;
-
-	ksp_esid_data = mk_esid_data(get_paca()->kstack, mmu_kernel_ssize, KSTACK_INDEX);
-	if ((ksp_esid_data & ~0xfffffffUL) <= PAGE_OFFSET) {
-		ksp_esid_data &= ~SLB_ESID_V;
-		ksp_vsid_data = 0;
-		slb_shadow_clear(KSTACK_INDEX);
-	} else {
-		/* Update stack entry; others don't change */
-		slb_shadow_update(get_paca()->kstack, mmu_kernel_ssize, lflags, KSTACK_INDEX);
-		ksp_vsid_data =
-			be64_to_cpu(get_slb_shadow()->save_area[KSTACK_INDEX].vsid);
-	}
-
-	/* We need to do this all in asm, so we're sure we don't touch
-	 * the stack between the slbia and rebolting it. */
 	asm volatile("isync\n"
 		     "slbia\n"
-		     /* Slot 1 - kernel stack */
-		     "slbmte	%0,%1\n"
-		     "isync"
-		     :: "r"(ksp_vsid_data),
-		        "r"(ksp_esid_data)
+		     "slbmte  %0, %1\n"
+		     "isync\n"
+		     :: "r" (be64_to_cpu(p->save_area[KSTACK_INDEX].vsid)),
+			"r" (be64_to_cpu(p->save_area[KSTACK_INDEX].esid))
 		     : "memory");
 
 	get_paca()->slb_cache_ptr = 0;
@@ -254,7 +237,10 @@ void slb_dump_contents(struct slb_entry *slb_ptr)
 
 void slb_vmalloc_update(void)
 {
-	slb_flush_and_rebolt();
+	/*
+	 * vmalloc is not bolted, so just have to flush non-bolted.
+	 */
+	slb_flush_and_restore_bolted();
 }
 
 static bool preload_hit(struct thread_info *ti, unsigned long esid)