1 files changed, 38 insertions, 34 deletions

diff --git a/arch/powerpc/kernel/syscall_64.c b/arch/powerpc/kernel/syscall_64.c
index 7b7c89cad901..79edba3ab312 100644
--- a/arch/powerpc/kernel/syscall_64.c
+++ b/arch/powerpc/kernel/syscall_64.c
@@ -102,6 +102,31 @@ notrace long system_call_exception(long r3, long r4, long r5,
 }
 
 /*
+ * local irqs must be disabled. Returns false if the caller must re-enable
+ * them, check for new work, and try again.
+ */
+static notrace inline bool prep_irq_for_enabled_exit(void)
+{
+	/* This must be done with RI=1 because tracing may touch vmaps */
+	trace_hardirqs_on();
+
+	/* This pattern matches prep_irq_for_idle */
+	__hard_EE_RI_disable();
+	if (unlikely(lazy_irq_pending_nocheck())) {
+		/* Took an interrupt, may have more exit work to do. */
+		__hard_RI_enable();
+		trace_hardirqs_off();
+		local_paca->irq_happened |= PACA_IRQ_HARD_DIS;
+
+		return false;
+	}
+	local_paca->irq_happened = 0;
+	irq_soft_mask_set(IRQS_ENABLED);
+
+	return true;
+}
+
+/*
  * This should be called after a syscall returns, with r3 the return value
  * from the syscall. If this function returns non-zero, the system call
  * exit assembly should additionally load all GPR registers and CTR and XER
@@ -186,21 +211,10 @@ again:
 		}
 	}
 
-	/* This must be done with RI=1 because tracing may touch vmaps */
-	trace_hardirqs_on();
-
-	/* This pattern matches prep_irq_for_idle */
-	__hard_EE_RI_disable();
-	if (unlikely(lazy_irq_pending_nocheck())) {
-		__hard_RI_enable();
-		trace_hardirqs_off();
-		local_paca->irq_happened |= PACA_IRQ_HARD_DIS;
+	if (unlikely(!prep_irq_for_enabled_exit())) {
 		local_irq_enable();
-		/* Took an interrupt, may have more exit work to do. */
 		goto again;
 	}
-	local_paca->irq_happened = 0;
-	irq_soft_mask_set(IRQS_ENABLED);
 
 #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
 	local_paca->tm_scratch = regs->msr;
@@ -228,6 +242,10 @@ notrace unsigned long interrupt_exit_user_prepare(struct pt_regs *regs, unsigned
 	BUG_ON(!FULL_REGS(regs));
 	BUG_ON(regs->softe != IRQS_ENABLED);
 
+	/*
+	 * We don't need to restore AMR on the way back to userspace for KUAP.
+	 * AMR can only have been unlocked if we interrupted the kernel.
+	 */
 	kuap_check_amr();
 
 	local_irq_save(flags);
@@ -264,19 +282,11 @@ again:
 		}
 	}
 
-	trace_hardirqs_on();
-	__hard_EE_RI_disable();
-	if (unlikely(lazy_irq_pending_nocheck())) {
-		__hard_RI_enable();
-		trace_hardirqs_off();
-		local_paca->irq_happened |= PACA_IRQ_HARD_DIS;
+	if (unlikely(!prep_irq_for_enabled_exit())) {
 		local_irq_enable();
 		local_irq_disable();
-		/* Took an interrupt, may have more exit work to do. */
 		goto again;
 	}
-	local_paca->irq_happened = 0;
-	irq_soft_mask_set(IRQS_ENABLED);
 
 #ifdef CONFIG_PPC_BOOK3E
 	if (unlikely(ts->debug.dbcr0 & DBCR0_IDM)) {
@@ -307,13 +317,14 @@ notrace unsigned long interrupt_exit_kernel_prepare(struct pt_regs *regs, unsign
 	unsigned long *ti_flagsp = &current_thread_info()->flags;
 	unsigned long flags;
 	unsigned long ret = 0;
+	unsigned long amr;
 
 	if (IS_ENABLED(CONFIG_PPC_BOOK3S) && unlikely(!(regs->msr & MSR_RI)))
 		unrecoverable_exception(regs);
 	BUG_ON(regs->msr & MSR_PR);
 	BUG_ON(!FULL_REGS(regs));
 
-	kuap_check_amr();
+	amr = kuap_get_and_check_amr();
 
 	if (unlikely(*ti_flagsp & _TIF_EMULATE_STACK_STORE)) {
 		clear_bits(_TIF_EMULATE_STACK_STORE, ti_flagsp);
@@ -334,13 +345,7 @@ again:
 			}
 		}
 
-		trace_hardirqs_on();
-		__hard_EE_RI_disable();
-		if (unlikely(lazy_irq_pending_nocheck())) {
-			__hard_RI_enable();
-			irq_soft_mask_set(IRQS_ALL_DISABLED);
-			trace_hardirqs_off();
-			local_paca->irq_happened |= PACA_IRQ_HARD_DIS;
+		if (unlikely(!prep_irq_for_enabled_exit())) {
 			/*
 			 * Can't local_irq_restore to replay if we were in
 			 * interrupt context. Must replay directly.
@@ -354,8 +359,6 @@ again:
 			/* Took an interrupt, may have more exit work to do. */
 			goto again;
 		}
-		local_paca->irq_happened = 0;
-		irq_soft_mask_set(IRQS_ENABLED);
 	} else {
 		/* Returning to a kernel context with local irqs disabled. */
 		__hard_EE_RI_disable();
@@ -369,10 +372,11 @@ again:
 #endif
 
 	/*
-	 * We don't need to restore AMR on the way back to userspace for KUAP.
-	 * The value of AMR only matters while we're in the kernel.
+	 * Don't want to mfspr(SPRN_AMR) here, because this comes after mtmsr,
+	 * which would cause Read-After-Write stalls. Hence, we take the AMR
+	 * value from the check above.
 	 */
-	kuap_restore_amr(regs);
+	kuap_restore_amr(regs, amr);
 
 	return ret;
 }