powerpc/64s/hash: Use POWER6 SLBIA IH=1 variant in switch_slb

The SLBIA IH=1 hint will remove all non-zero SLBEs, but only
invalidate ERAT entries associated with a class value of 1, for
processors that support the hint (e.g., POWER6 and newer), which
Linux assigns to user addresses.

This prevents kernel ERAT entries from being invalidated when
context switchig (if the thread faulted in more than 8 user SLBEs).
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/mm/slb.c

@@ -128,13 +128,21 @@ void slb_flush_all_realmode(void)
 	asm volatile("slbmte %0,%0; slbia" : : "r" (0));
 }
 
-static void __slb_flush_and_rebolt(void)
+void slb_flush_and_rebolt(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;
 
+	WARN_ON(!irqs_disabled());
+
+	/*
+	 * We can't take a PMU exception in the following code, so hard
+	 * disable interrupts.
+	 */
+	hard_irq_disable();
+
 	linear_llp = mmu_psize_defs[mmu_linear_psize].sllp;
 	lflags = SLB_VSID_KERNEL | linear_llp;
 
@@ -160,20 +168,7 @@ static void __slb_flush_and_rebolt(void)
 		     :: "r"(ksp_vsid_data),
 		        "r"(ksp_esid_data)
 		     : "memory");
-}
-
-void slb_flush_and_rebolt(void)
-{
-
-	WARN_ON(!irqs_disabled());
 
-	/*
-	 * We can't take a PMU exception in the following code, so hard
-	 * disable interrupts.
-	 */
-	hard_irq_disable();
-
-	__slb_flush_and_rebolt();
 	get_paca()->slb_cache_ptr = 0;
 }
 
@@ -318,7 +313,20 @@ void switch_slb(struct task_struct *tsk, struct mm_struct *mm)
 
 		asm volatile("isync" : : : "memory");
 	} else {
-		__slb_flush_and_rebolt();
+		struct slb_shadow *p = get_slb_shadow();
+		unsigned long ksp_esid_data =
+			be64_to_cpu(p->save_area[KSTACK_INDEX].esid);
+		unsigned long ksp_vsid_data =
+			be64_to_cpu(p->save_area[KSTACK_INDEX].vsid);
+
+		asm volatile("isync\n"
+			     PPC_SLBIA(1) "\n"
+			     "slbmte	%0,%1\n"
+			     "isync"
+			     :: "r"(ksp_vsid_data),
+				"r"(ksp_esid_data));
+
+		asm volatile("isync" : : : "memory");
 	}
 
 	get_paca()->slb_cache_ptr = 0;