[PATCH v2 11/11] powerpc/64: use interrupt restart table to speed up return from interrupt

@@ -18,8 +18,17 @@
  * PACA flags in paca->irq_happened.
  *
  * This bits are set when interrupts occur while soft-disabled
- * and allow a proper replay. Additionally, PACA_IRQ_HARD_DIS
- * is set whenever we manually hard disable.
+ * and allow a proper replay.
+ *
+ * The PACA_IRQ_HARD_DIS is set whenever we hard disable. It is almost
+ * always in synch with the MSR[EE] state, except:
+ * - A window in interrupt entry, where hardware disables MSR[EE] and that
+ *   must be "reconciled" with the soft mask state.
+ * - NMI interrupts that hit in awkward places, until they fix the state.
+ * - When local irqs are being enabled and state is being fixed up.
+ * - When returning from an interrupt there are some windows where this
+ *   can become out of synch, but gets fixed before the RFI or before
+ *   executing the next user instruction (see arch/powerpc/kernel/interrupt.c).
  */
 #define PACA_IRQ_HARD_DIS	0x01
 #define PACA_IRQ_DBELL		0x02

@@ -79,6 +79,8 @@ unsigned long search_kernel_restart_table(unsigned long addr);
 #endif
 
 #ifdef CONFIG_PPC_BOOK3S_64
+DECLARE_STATIC_KEY_FALSE(interrupt_exit_not_reentrant);
+
 static inline void srr_regs_clobbered(void)
 {
 	local_paca->srr_valid = 0;

@@ -167,6 +167,9 @@ struct paca_struct {
 	u64 kstack;			/* Saved Kernel stack addr */
 	u64 saved_r1;			/* r1 save for RTAS calls or PM or EE=0 */
 	u64 saved_msr;			/* MSR saved here by enter_rtas */
+#ifdef CONFIG_PPC64
+	u64 exit_save_r1;		/* Syscall/interrupt R1 save */
+#endif
 #ifdef CONFIG_PPC_BOOK3E
 	u16 trap_save;			/* Used when bad stack is encountered */
 #endif

@@ -52,6 +52,7 @@ struct pt_regs
 		struct {
 #ifdef CONFIG_PPC64
 			unsigned long ppr;
+			unsigned long exit_result;
 #endif
 			union {
 #ifdef CONFIG_PPC_KUAP

@@ -286,6 +286,9 @@ int main(void)
 	OFFSET(PACAHWCPUID, paca_struct, hw_cpu_id);
 	OFFSET(PACAKEXECSTATE, paca_struct, kexec_state);
 	OFFSET(PACA_DSCR_DEFAULT, paca_struct, dscr_default);
+#ifdef CONFIG_PPC64
+	OFFSET(PACA_EXIT_SAVE_R1, paca_struct, exit_save_r1);
+#endif
 #ifdef CONFIG_PPC_BOOK3E
 	OFFSET(PACA_TRAP_SAVE, paca_struct, trap_save);
 #endif

@@ -26,6 +26,83 @@ unsigned long global_dbcr0[NR_CPUS];
 
 typedef long (*syscall_fn)(long, long, long, long, long, long);
 
+#ifdef CONFIG_PPC_BOOK3S_64
+DEFINE_STATIC_KEY_FALSE(interrupt_exit_not_reentrant);
+static inline bool exit_must_hard_disable(void)
+{
+	return static_branch_unlikely(&interrupt_exit_not_reentrant);
+}
+#else
+static inline bool exit_must_hard_disable(void)
+{
+	return false;
+}
+#endif
+
+/*
+ * local irqs must be disabled. Returns false if the caller must re-enable
+ * them, check for new work, and try again.
+ *
+ * This should be called with local irqs disabled, but if they were previously
+ * enabled when the interrupt handler returns (indicating a process-context /
+ * synchronous interrupt) then irqs_enabled should be true.
+ */
+static notrace __always_inline bool prep_irq_for_user_exit(void)
+{
+	user_enter_irqoff();
+	/* This must be done with RI=1 because tracing may touch vmaps */
+	trace_hardirqs_on();
+
+#ifdef CONFIG_PPC32
+	__hard_EE_RI_disable();
+#else
+	if (exit_must_hard_disable())
+		__hard_EE_RI_disable();
+
+	/* This pattern matches prep_irq_for_idle */
+	if (unlikely(lazy_irq_pending_nocheck())) {
+		if (exit_must_hard_disable()) {
+			local_paca->irq_happened |= PACA_IRQ_HARD_DIS;
+			__hard_RI_enable();
+		}
+		trace_hardirqs_off();
+		user_exit_irqoff();
+
+		return false;
+	}
+#endif
+	return true;
+}
+
+/*
+ * restartable is true then EE/RI can be left on because interrupts are handled
+ * with a restart sequence.
+ */
+static notrace __always_inline bool prep_irq_for_kernel_enabled_exit(bool restartable)
+{
+	/* This must be done with RI=1 because tracing may touch vmaps */
+	trace_hardirqs_on();
+
+#ifdef CONFIG_PPC32
+	__hard_EE_RI_disable();
+#else
+	if (exit_must_hard_disable() || !restartable)
+		__hard_EE_RI_disable();
+
+	/* This pattern matches prep_irq_for_idle */
+	if (unlikely(lazy_irq_pending_nocheck())) {
+		if (exit_must_hard_disable() || !restartable) {
+			local_paca->irq_happened |= PACA_IRQ_HARD_DIS;
+			__hard_RI_enable();
+		}
+		trace_hardirqs_off();
+
+		return false;
+	}
+#endif
+	return true;
+}
+
 /* Has to run notrace because it is entered not completely "reconciled" */
 notrace long system_call_exception(long r3, long r4, long r5,
 				   long r6, long r7, long r8,

@@ -144,71 +221,6 @@ notrace long system_call_exception(long r3, long r4, long r5,
 	return f(r3, r4, r5, r6, r7, r8);
 }
 
-/*
- * local irqs must be disabled. Returns false if the caller must re-enable
- * them, check for new work, and try again.
- *
- * This should be called with local irqs disabled, but if they were previously
- * enabled when the interrupt handler returns (indicating a process-context /
- * synchronous interrupt) then irqs_enabled should be true.
- */
-static notrace __always_inline bool __prep_irq_for_enabled_exit(bool clear_ri)
-{
-	/* This must be done with RI=1 because tracing may touch vmaps */
-	trace_hardirqs_on();
-
-	/* This pattern matches prep_irq_for_idle */
-	if (clear_ri)
-		__hard_EE_RI_disable();
-	else
-		__hard_irq_disable();
-#ifdef CONFIG_PPC64
-	if (unlikely(lazy_irq_pending_nocheck())) {
-		/* Took an interrupt, may have more exit work to do. */
-		if (clear_ri)
-			__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);
-#endif
-	return true;
-}
-
-static notrace inline bool prep_irq_for_enabled_exit(bool clear_ri, bool irqs_enabled)
-{
-	if (__prep_irq_for_enabled_exit(clear_ri))
-		return true;
-
-	/*
-	 * Must replay pending soft-masked interrupts now. Don't just
-	 * local_irq_enabe(); local_irq_disable(); because if we are
-	 * returning from an asynchronous interrupt here, another one
-	 * might hit after irqs are enabled, and it would exit via this
-	 * same path allowing another to fire, and so on unbounded.
-	 *
-	 * If interrupts were enabled when this interrupt exited,
-	 * indicating a process context (synchronous) interrupt,
-	 * local_irq_enable/disable can be used, which will enable
-	 * interrupts rather than keeping them masked (unclear how
-	 * much benefit this is over just replaying for all cases,
-	 * because we immediately disable again, so all we're really
-	 * doing is allowing hard interrupts to execute directly for
-	 * a very small time, rather than being masked and replayed).
-	 */
-	if (irqs_enabled) {
-		local_irq_enable();
-		local_irq_disable();
-	} else {
-		replay_soft_interrupts();
-	}
-
-	return false;
-}
-
 static notrace void booke_load_dbcr0(void)
 {
 #ifdef CONFIG_PPC_ADV_DEBUG_REGS

@@ -231,57 +243,11 @@ static notrace void booke_load_dbcr0(void)
 #endif
 }
 
-/*
- * 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
- * from the interrupt frame.
- *
- * The function graph tracer can not trace the return side of this function,
- * because RI=0 and soft mask state is "unreconciled", so it is marked notrace.
- */
-notrace unsigned long syscall_exit_prepare(unsigned long r3,
-					   struct pt_regs *regs,
-					   long scv)
+notrace unsigned long syscall_exit_prepare_main(unsigned long r3,
+						struct pt_regs *regs)
 {
 	unsigned long ti_flags;
 	unsigned long ret = 0;
-	bool is_not_scv = !IS_ENABLED(CONFIG_PPC_BOOK3S_64) || !scv;
-
-	CT_WARN_ON(ct_state() == CONTEXT_USER);
-
-	kuap_assert_locked();
-
-	regs->result = r3;
-
-	/* Check whether the syscall is issued inside a restartable sequence */
-	rseq_syscall(regs);
-
-	ti_flags = current_thread_info()->flags;
-
-	if (unlikely(r3 >= (unsigned long)-MAX_ERRNO) && is_not_scv) {
-		if (likely(!(ti_flags & (_TIF_NOERROR | _TIF_RESTOREALL)))) {
-			r3 = -r3;
-			regs->ccr |= 0x10000000; /* Set SO bit in CR */
-		}
-	}
-
-	if (unlikely(ti_flags & _TIF_PERSYSCALL_MASK)) {
-		if (ti_flags & _TIF_RESTOREALL)
-			ret = _TIF_RESTOREALL;
-		else
-			regs->gpr[3] = r3;
-		clear_bits(_TIF_PERSYSCALL_MASK, &current_thread_info()->flags);
-	} else {
-		regs->gpr[3] = r3;
-	}
-
-	if (unlikely(ti_flags & _TIF_SYSCALL_DOTRACE)) {
-		do_syscall_trace_leave(regs);
-		ret |= _TIF_RESTOREALL;
-	}
-
-	local_irq_disable();
 
 again:
 	ti_flags = READ_ONCE(current_thread_info()->flags);

@@ -327,11 +293,7 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3,
 		}
 	}
 
-	user_enter_irqoff();
-
-	/* scv need not set RI=0 because SRRs are not used */
-	if (unlikely(!__prep_irq_for_enabled_exit(is_not_scv))) {
-		user_exit_irqoff();
+	if (!prep_irq_for_user_exit()) {
 		local_irq_enable();
 		local_irq_disable();
 		goto again;

@@ -352,6 +314,91 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3,
 	return ret;
 }
 
+/*
+ * 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
+ * from the interrupt frame.
+ *
+ * The function graph tracer can not trace the return side of this function,
+ * because RI=0 and soft mask state is "unreconciled", so it is marked notrace.
+ */
+notrace unsigned long syscall_exit_prepare(unsigned long r3,
+					   struct pt_regs *regs,
+					   long scv)
+{
+	unsigned long ti_flags;
+	unsigned long ret = 0;
+	bool is_not_scv = !IS_ENABLED(CONFIG_PPC_BOOK3S_64) || !scv;
+
+	CT_WARN_ON(ct_state() == CONTEXT_USER);
+
+	kuap_assert_locked();
+
+	regs->result = r3;
+
+	/* Check whether the syscall is issued inside a restartable sequence */
+	rseq_syscall(regs);
+
+	ti_flags = current_thread_info()->flags;
+
+	if (unlikely(r3 >= (unsigned long)-MAX_ERRNO) && is_not_scv) {
+		if (likely(!(ti_flags & (_TIF_NOERROR | _TIF_RESTOREALL)))) {
+			r3 = -r3;
+			regs->ccr |= 0x10000000; /* Set SO bit in CR */
+		}
+	}
+
+	if (unlikely(ti_flags & _TIF_PERSYSCALL_MASK)) {
+		if (ti_flags & _TIF_RESTOREALL)
+			ret = _TIF_RESTOREALL;
+		else
+			regs->gpr[3] = r3;
+		clear_bits(_TIF_PERSYSCALL_MASK, &current_thread_info()->flags);
+	} else {
+		regs->gpr[3] = r3;
+	}
+
+	if (unlikely(ti_flags & _TIF_SYSCALL_DOTRACE)) {
+		do_syscall_trace_leave(regs);
+		ret |= _TIF_RESTOREALL;
+	}
+
+	local_irq_disable();
+	ret |= syscall_exit_prepare_main(r3, regs);
+
+#ifdef CONFIG_PPC64
+	regs->exit_result = ret;
+#endif
+
+	return ret;
+}
+
+#ifdef CONFIG_PPC64
+notrace unsigned long syscall_exit_restart(unsigned long r3, struct pt_regs *regs)
+{
+	/*
+	 * This is called when detecting a soft-pending interrupt as well as
+	 * an alternate-return interrupt. So we can't just have the alternate
+	 * return path clear SRR1[MSR] and set PACA_IRQ_HARD_DIS (unless
+	 * the soft-pending case were to fix things up as well). RI might be
+	 * disabled, in which case it gets re-enabled by __hard_irq_disable().
+	 */
+	__hard_irq_disable();
+	local_paca->irq_happened |= PACA_IRQ_HARD_DIS;
+
+	trace_hardirqs_off();
+	user_exit_irqoff();
+	account_cpu_user_entry();
+
+	BUG_ON(!user_mode(regs));
+
+	regs->exit_result |= syscall_exit_prepare_main(r3, regs);
+
+	return regs->exit_result;
+}
+#endif
+
 notrace unsigned long interrupt_exit_user_prepare(struct pt_regs *regs)
 {
 	unsigned long ti_flags;

@@ -405,10 +452,7 @@ notrace unsigned long interrupt_exit_user_prepare(struct pt_regs *regs)
 		}
 	}
 
-	user_enter_irqoff();
-
-	if (unlikely(!__prep_irq_for_enabled_exit(true))) {
-		user_exit_irqoff();
+	if (!prep_irq_for_user_exit()) {
 		local_irq_enable();
 		local_irq_disable();
 		goto again;

@@ -422,6 +466,10 @@ notrace unsigned long interrupt_exit_user_prepare(struct pt_regs *regs)
 
 	account_cpu_user_exit();
 
+#ifdef CONFIG_PPC64
+	regs->exit_result = ret;
+#endif
+
 	/* Restore user access locks last */
 	kuap_user_restore(regs);
 	kuep_unlock();

@@ -436,6 +484,8 @@ notrace unsigned long interrupt_exit_kernel_prepare(struct pt_regs *regs)
 	unsigned long flags;
 	unsigned long ret = 0;
 	unsigned long kuap;
+	bool stack_store = current_thread_info()->flags &
+						_TIF_EMULATE_STACK_STORE;
 
 	if (!IS_ENABLED(CONFIG_BOOKE) && !IS_ENABLED(CONFIG_40x) &&
 	    unlikely(!(regs->msr & MSR_RI)))

@@ -450,11 +500,6 @@ notrace unsigned long interrupt_exit_kernel_prepare(struct pt_regs *regs)
 
 	kuap = kuap_get_and_assert_locked();
 
-	if (unlikely(current_thread_info()->flags & _TIF_EMULATE_STACK_STORE)) {
-		clear_bits(_TIF_EMULATE_STACK_STORE, &current_thread_info()->flags);
-		ret = 1;
-	}
-
 	local_irq_save(flags);
 
 	if (!arch_irq_disabled_regs(regs)) {

@@ -469,17 +514,54 @@ notrace unsigned long interrupt_exit_kernel_prepare(struct pt_regs *regs)
 			}
 		}
 
-		if (unlikely(!prep_irq_for_enabled_exit(true, !irqs_disabled_flags(flags))))
+		/*
+		 * Stack store exit can't be restarted because the interrupt
+		 * stack frame might have been clobbered.
+		 */
+		if (!prep_irq_for_kernel_enabled_exit(unlikely(stack_store))) {
+			/*
+			 * Replay pending soft-masked interrupts now. Don't
+			 * just local_irq_enabe(); local_irq_disable(); because
+			 * if we are returning from an asynchronous interrupt
+			 * here, another one might hit after irqs are enabled,
+			 * and it would exit via this same path allowing
+			 * another to fire, and so on unbounded.
+			 */
+			hard_irq_disable();
+			replay_soft_interrupts();
+			/* Took an interrupt, may have more exit work to do. */
 			goto again;
-	} else {
-		/* Returning to a kernel context with local irqs disabled. */
-		__hard_EE_RI_disable();
+		}
 #ifdef CONFIG_PPC64
+		/*
+		 * An interrupt may clear MSR[EE] and set this concurrently,
+		 * but it will be marked pending and the exit will be retried.
+		 * This leaves a racy window where MSR[EE]=0 and HARD_DIS is
+		 * clear, until interrupt_exit_kernel_restart() calls
+		 * hard_irq_disable(), which will set HARD_DIS again.
+		 */
+		local_paca->irq_happened &= ~PACA_IRQ_HARD_DIS;
+
+	} else {
+		if (unlikely(stack_store))
+			__hard_EE_RI_disable();
+		/*
+		 * Returning to a kernel context with local irqs disabled.
+		 * Here, if EE was enabled in the interrupted context, enable
+		 * it on return as well. A problem exists here where a soft
+		 * masked interrupt may have cleared MSR[EE] and set HARD_DIS
+		 * here, and it will still exist on return to the caller. This
+		 * will be resolved by the masked interrupt firing again.
+		 */
 		if (regs->msr & MSR_EE)
 			local_paca->irq_happened &= ~PACA_IRQ_HARD_DIS;
-#endif
+#endif /* CONFIG_PPC64 */
 	}
 
+	if (unlikely(stack_store)) {
+		clear_bits(_TIF_EMULATE_STACK_STORE, &current_thread_info()->flags);
+		ret = 1;
+	}
 
 #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
 	local_paca->tm_scratch = regs->msr;

@@ -494,3 +576,42 @@ notrace unsigned long interrupt_exit_kernel_prepare(struct pt_regs *regs)
 
 	return ret;
 }
+
+#ifdef CONFIG_PPC64
+notrace unsigned long interrupt_exit_user_restart(struct pt_regs *regs)
+{
+	__hard_irq_disable();
+	local_paca->irq_happened |= PACA_IRQ_HARD_DIS;
+
+	trace_hardirqs_off();
+	user_exit_irqoff();
+	account_cpu_user_entry();
+
+	BUG_ON(!user_mode(regs));
+
+	regs->exit_result |= interrupt_exit_user_prepare(regs);
+
+	return regs->exit_result;
+}
+
+/*
+ * No real need to return a value here because the stack store case does not
+ * get restarted.
+ */
+notrace unsigned long interrupt_exit_kernel_restart(struct pt_regs *regs)
+{
+	__hard_irq_disable();
+	local_paca->irq_happened |= PACA_IRQ_HARD_DIS;
+
+#ifdef CONFIG_PPC_BOOK3S_64
+	set_kuap(AMR_KUAP_BLOCKED);
+#endif
+
+	if (regs->softe == IRQS_ENABLED)
+		trace_hardirqs_off();
+
+	BUG_ON(user_mode(regs));
+
+	return interrupt_exit_kernel_prepare(regs);
+}
+#endif

@@ -117,9 +117,18 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
 	bl	system_call_exception
 
 .Lsyscall_vectored_\name\()_exit:
-	addi    r4,r1,STACK_FRAME_OVERHEAD
+	addi	r4,r1,STACK_FRAME_OVERHEAD
 	li	r5,1 /* scv */
 	bl	syscall_exit_prepare
+	std	r1,PACA_EXIT_SAVE_R1(r13) /* save r1 for restart */
+.Lsyscall_vectored_\name\()_rst_start:
+	lbz	r11,PACAIRQHAPPENED(r13)
+	andi.	r11,r11,(~PACA_IRQ_HARD_DIS)@l
+	bne-	.Lsyscall_vectored_\name\()_restart
+	li	r11,IRQS_ENABLED
+	stb	r11,PACAIRQSOFTMASK(r13)
+	li	r11,0
+	stb	r11,PACAIRQHAPPENED(r13) # clear out possible HARD_DIS
 
 	ld	r2,_CCR(r1)
 	ld	r4,_NIP(r1)

@@ -169,8 +178,6 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
 	b	.	/* prevent speculative execution */
 
 .Lsyscall_vectored_\name\()_restore_regs:
-	li	r3,0
-	mtmsrd	r3,1
 	mtspr	SPRN_SRR0,r4
 	mtspr	SPRN_SRR1,r5
 

@@ -188,9 +195,26 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
 	REST_2GPRS(12, r1)
 	ld	r1,GPR1(r1)
 	RFI_TO_USER
+.Lsyscall_vectored_\name\()_rst_end:
+
+.Lsyscall_vectored_\name\()_restart:
+	GET_PACA(r13)
+	ld	r1,PACA_EXIT_SAVE_R1(r13)
+	ld	r2,PACATOC(r13)
+	ld	r3,RESULT(r1)
+	addi	r4,r1,STACK_FRAME_OVERHEAD
+	li	r11,IRQS_ALL_DISABLED
+	stb	r11,PACAIRQSOFTMASK(r13)
+	bl	syscall_exit_restart
+	std	r1,PACA_EXIT_SAVE_R1(r13) /* save r1 for restart */
+	b	.Lsyscall_vectored_\name\()_rst_start
+
+RESTART_TABLE(.Lsyscall_vectored_\name\()_rst_start, .Lsyscall_vectored_\name\()_rst_end, .Lsyscall_vectored_\name\()_restart)
+
 .endm
 
 system_call_vectored common 0x3000
+
 /*
  * We instantiate another entry copy for the SIGILL variant, with TRAP=0x7ff0
  * which is tested by system_call_exception when r0 is -1 (as set by vector

@@ -293,9 +317,18 @@ END_BTB_FLUSH_SECTION
 	bl	system_call_exception
 
 .Lsyscall_exit:
-	addi    r4,r1,STACK_FRAME_OVERHEAD
+	addi	r4,r1,STACK_FRAME_OVERHEAD
 	li	r5,0 /* !scv */
 	bl	syscall_exit_prepare
+	std	r1,PACA_EXIT_SAVE_R1(r13) /* save r1 for restart */
+.Lsyscall_rst_start:
+	lbz	r11,PACAIRQHAPPENED(r13)
+	andi.	r11,r11,(~PACA_IRQ_HARD_DIS)@l
+	bne-	.Lsyscall_restart
+	li	r11,IRQS_ENABLED
+	stb	r11,PACAIRQSOFTMASK(r13)
+	li	r11,0
+	stb	r11,PACAIRQHAPPENED(r13) # clear out possible HARD_DIS
 
 	ld	r2,_CCR(r1)
 	ld	r6,_LINK(r1)

@@ -362,6 +395,21 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
 	REST_8GPRS(4, r1)
 	ld	r12,GPR12(r1)
 	b	.Lsyscall_restore_regs_cont
+.Lsyscall_rst_end:
+
+.Lsyscall_restart:
+	GET_PACA(r13)
+	ld	r1,PACA_EXIT_SAVE_R1(r13)
+	ld	r2,PACATOC(r13)
+	ld	r3,RESULT(r1)
+	addi	r4,r1,STACK_FRAME_OVERHEAD
+	li	r11,IRQS_ALL_DISABLED
+	stb	r11,PACAIRQSOFTMASK(r13)
+	bl	syscall_exit_restart
+	std	r1,PACA_EXIT_SAVE_R1(r13) /* save r1 for restart */
+	b	.Lsyscall_rst_start
+
+RESTART_TABLE(.Lsyscall_rst_start, .Lsyscall_rst_end, .Lsyscall_restart)
 
 #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
 .Ltabort_syscall:

@@ -449,21 +497,28 @@ _ASM_NOKPROBE_SYMBOL(interrupt_return_\srr\())
 	ld	r4,_MSR(r1)
 	andi.	r0,r4,MSR_PR
 	beq	.Lkernel_interrupt_return_\srr
+.Linterrupt_return_\srr\()_user:
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 	bl	interrupt_exit_user_prepare
 	cmpdi	r3,0
 	bne-	.Lrestore_nvgprs_\srr
+.Lrestore_nvgprs_\srr\()_cont:
 
 #ifdef CONFIG_PPC_BOOK3S
 .Lfast_user_interrupt_return_amr_\srr\():
 	kuap_user_restore r3, r4
 #endif
-.Lfast_user_interrupt_return_\srr\():
-
-BEGIN_FTR_SECTION
-	ld	r10,_PPR(r1)
-	mtspr	SPRN_PPR,r10
-END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
+// .Lfast_user_interrupt_return_\srr\():
+
+	std	r1,PACA_EXIT_SAVE_R1(r13) /* save r1 for restart */
+.Linterrupt_return_\srr\()_user_rst_start:
+	lbz	r11,PACAIRQHAPPENED(r13)
+	andi.	r11,r11,(~PACA_IRQ_HARD_DIS)@l
+	bne-	.Linterrupt_return_\srr\()_user_restart
+	li	r11,IRQS_ENABLED
+	stb	r11,PACAIRQSOFTMASK(r13)
+	li	r11,0
+	stb	r11,PACAIRQHAPPENED(r13) # clear out possible HARD_DIS
 
 #ifdef CONFIG_PPC_BOOK3S
 	.ifc \srr,srr

@@ -494,6 +549,17 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
 	.endif
 	DEBUG_SRR_VALID \srr
 
+.Lfast_user_interrupt_return_\srr\():
+#ifdef CONFIG_PPC_IRQ_SOFT_MASK_DEBUG
+	lbz	r4,PACAIRQSOFTMASK(r13)
+	tdnei	r4,IRQS_ENABLED
+#endif
+
+BEGIN_FTR_SECTION
+	ld	r10,_PPR(r1)
+	mtspr	SPRN_PPR,r10
+END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
+
 BEGIN_FTR_SECTION
 	stdcx.	r0,0,r1		/* to clear the reservation */
 FTR_SECTION_ELSE

@@ -525,16 +591,44 @@ ALT_FTR_SECTION_END_IFCLR(CPU_FTR_STCX_CHECKS_ADDRESS)
 	HRFI_TO_USER
 	.endif
 	b	.	/* prevent speculative execution */
+.Linterrupt_return_\srr\()_user_rst_end:
 
 .Lrestore_nvgprs_\srr\():
 	REST_NVGPRS(r1)
-	b	.Lfast_user_interrupt_return_\srr
+	b	.Lrestore_nvgprs_\srr\()_cont
+
+.Linterrupt_return_\srr\()_user_restart:
+	GET_PACA(r13)
+	ld	r1,PACA_EXIT_SAVE_R1(r13)
+	ld	r2,PACATOC(r13)
+	addi	r3,r1,STACK_FRAME_OVERHEAD
+	li	r11,IRQS_ALL_DISABLED
+	stb	r11,PACAIRQSOFTMASK(r13)
+	bl	interrupt_exit_user_restart
+	std	r1,PACA_EXIT_SAVE_R1(r13) /* save r1 for restart */
+	b	.Linterrupt_return_\srr\()_user_rst_start
+
+RESTART_TABLE(.Linterrupt_return_\srr\()_user_rst_start, .Linterrupt_return_\srr\()_user_rst_end, .Linterrupt_return_\srr\()_user_restart)
 
 	.balign IFETCH_ALIGN_BYTES
 .Lkernel_interrupt_return_\srr\():
+.Linterrupt_return_\srr\()_kernel:
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 	bl	interrupt_exit_kernel_prepare
 
+	std	r1,PACA_EXIT_SAVE_R1(r13) /* save r1 for restart */
+.Linterrupt_return_\srr\()_kernel_rst_start:
+	lbz	r11,SOFTE(r1)
+	cmpwi	r11,IRQS_ENABLED
+	stb	r11,PACAIRQSOFTMASK(r13)
+	bne	1f
+	lbz	r11,PACAIRQHAPPENED(r13)
+	andi.	r11,r11,(~PACA_IRQ_HARD_DIS)@l
+	bne-	.Linterrupt_return_\srr\()_kernel_restart
+	li	r11,0
+	stb	r11,PACAIRQHAPPENED(r13) # clear out possible HARD_DIS
+1:
+
 .Lfast_kernel_interrupt_return_\srr\():
 	cmpdi	cr1,r3,0
 #ifdef CONFIG_PPC_BOOK3S

@@ -628,6 +722,21 @@ ALT_FTR_SECTION_END_IFCLR(CPU_FTR_STCX_CHECKS_ADDRESS)
 	HRFI_TO_KERNEL
 	.endif
 	b	.	/* prevent speculative execution */
+.Linterrupt_return_\srr\()_kernel_rst_end:
+
+.Linterrupt_return_\srr\()_kernel_restart:
+	GET_PACA(r13)
+	ld	r1,PACA_EXIT_SAVE_R1(r13)
+	ld	r2,PACATOC(r13)
+	addi	r3,r1,STACK_FRAME_OVERHEAD
+	li	r11,IRQS_ALL_DISABLED
+	stb	r11,PACAIRQSOFTMASK(r13)
+	bl	interrupt_exit_kernel_restart
+	std	r1,PACA_EXIT_SAVE_R1(r13) /* save r1 for restart */
+	b	.Linterrupt_return_\srr\()_kernel_rst_start
+
+RESTART_TABLE(.Linterrupt_return_\srr\()_kernel_rst_start, .Linterrupt_return_\srr\()_kernel_rst_end, .Linterrupt_return_\srr\()_kernel_restart)
+
 .endm
 
 interrupt_return_macro srr

@@ -17,6 +17,7 @@
 #include <linux/stop_machine.h>
 #include <asm/cputable.h>
 #include <asm/code-patching.h>
+#include <asm/interrupt.h>
 #include <asm/page.h>
 #include <asm/sections.h>
 #include <asm/setup.h>

@@ -228,10 +229,27 @@ static void do_stf_exit_barrier_fixups(enum stf_barrier_type types)
 		                                           : "unknown");
 }
 
+static bool stf_exit_not_reentrant = false;
+static bool rfi_exit_not_reentrant = false;
+
+static void update_interrupt_exit(void)
+{
+	if (stf_exit_not_reentrant || rfi_exit_not_reentrant)
+		static_branch_enable(&interrupt_exit_not_reentrant);
+	else
+		static_branch_disable(&interrupt_exit_not_reentrant);
+}
+
 static int __do_stf_barrier_fixups(void *data)
 {
 	enum stf_barrier_type *types = data;
 
+	if (*types & STF_BARRIER_FALLBACK || *types & STF_BARRIER_SYNC_ORI)
+		stf_exit_not_reentrant = true;
+	else
+		stf_exit_not_reentrant = false;
+	update_interrupt_exit();
+
 	do_stf_entry_barrier_fixups(*types);
 	do_stf_exit_barrier_fixups(*types);
 

@@ -412,12 +430,19 @@ void do_entry_flush_fixups(enum l1d_flush_type types)
 	stop_machine(__do_entry_flush_fixups, &types, NULL);
 }
 
-void do_rfi_flush_fixups(enum l1d_flush_type types)
+static int __do_rfi_flush_fixups(void *data)
 {
+	enum l1d_flush_type types = *(enum l1d_flush_type *)data;
 	unsigned int instrs[3], *dest;
 	long *start, *end;
 	int i;
 
+	if (types & L1D_FLUSH_FALLBACK)
+		rfi_exit_not_reentrant = true;
+	else
+		rfi_exit_not_reentrant = false;
+	update_interrupt_exit();
+
 	start = PTRRELOC(&__start___rfi_flush_fixup);
 	end = PTRRELOC(&__stop___rfi_flush_fixup);
 

@@ -456,6 +481,17 @@ void do_rfi_flush_fixups(enum l1d_flush_type types)
 							: "ori type" :
 		(types &  L1D_FLUSH_MTTRIG)     ? "mttrig type"
 						: "unknown");
+
+	return 0;
+}
+
+void do_rfi_flush_fixups(enum l1d_flush_type types)
+{
+	/*
+	 * The interrupt_exit_not_reentrant static branch together with the
+	 * patching is not safe to perform while other CPUs are executing.
+	 */
+	stop_machine(__do_rfi_flush_fixups, &types, NULL);
 }
 
 void do_barrier_nospec_fixups_range(bool enable, void *fixup_start, void *fixup_end)