powerpc/64s: Implement interrupt exit logic in C

Implement the bulk of interrupt return logic in C. The asm return code
must handle a few cases: restoring full GPRs, and emulating stack
store.

The stack store emulation is significantly simplfied, rather than
creating a new return frame and switching to that before performing
the store, it uses the PACA to keep a scratch register around to
perform the store.

The asm return code is moved into 64e for now. The new logic has made
allowance for 64e, but I don't have a full environment that works well
to test it, and even booting in emulated qemu is not great for stress
testing. 64e shouldn't be too far off working with this, given a bit
more testing and auditing of the logic.

This is slightly faster on a POWER9 (page fault speed increases about
1.1%), probably due to reduced mtmsrd.

mpe: Includes fixes from Nick for _TIF_EMULATE_STACK_STORE
handling (including the fast_interrupt_return path), to remove
trace_hardirqs_on(), and fixes the interrupt-return part of the
MSR_VSX restore bug caught by tm-unavailable selftest.

mpe: Incorporate fix from Nick:

The return-to-kernel path has to replay any soft-pending interrupts if
it is returning to a context that had interrupts soft-enabled. It has
to do this carefully and avoid plain enabling interrupts if this is an
irq context, which can cause multiple nesting of interrupts on the
stack, and other unexpected issues.

The code which avoided this case got the soft-mask state wrong, and
marked interrupts as enabled before going around again to retry. This
seems to be mostly harmless except when PREEMPT=y, this calls
preempt_schedule_irq with irqs apparently enabled and runs into a BUG
in kernel/sched/core.c
Signed-off-by: NNicholas Piggin <npiggin@gmail.com>
Signed-off-by: NMichal Suchanek <msuchanek@suse.de>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200225173541.1549955-29-npiggin@gmail.com

arch/powerpc/include/asm/asm-prototypes.h

@@ -99,6 +99,8 @@ void __init machine_init(u64 dt_ptr);
 #endif
 long system_call_exception(long r3, long r4, long r5, long r6, long r7, long r8, unsigned long r0, struct pt_regs *regs);
 notrace unsigned long syscall_exit_prepare(unsigned long r3, struct pt_regs *regs);
+notrace unsigned long interrupt_exit_user_prepare(struct pt_regs *regs, unsigned long msr);
+notrace unsigned long interrupt_exit_kernel_prepare(struct pt_regs *regs, unsigned long msr);
 
 long ppc_fadvise64_64(int fd, int advice, u32 offset_high, u32 offset_low,
 		      u32 len_high, u32 len_low);

arch/powerpc/include/asm/book3s/64/kup-radix.h

@@ -60,6 +60,12 @@
 #include <asm/mmu.h>
 #include <asm/ptrace.h>
 
+static inline void kuap_restore_amr(struct pt_regs *regs)
+{
+	if (mmu_has_feature(MMU_FTR_RADIX_KUAP))
+		mtspr(SPRN_AMR, regs->kuap);
+}
+
 static inline void kuap_check_amr(void)
 {
 	if (IS_ENABLED(CONFIG_PPC_KUAP_DEBUG) && mmu_has_feature(MMU_FTR_RADIX_KUAP))
@@ -136,6 +142,10 @@ bad_kuap_fault(struct pt_regs *regs, unsigned long address, bool is_write)
 		    "Bug: %s fault blocked by AMR!", is_write ? "Write" : "Read");
 }
 #else /* CONFIG_PPC_KUAP */
+static inline void kuap_restore_amr(struct pt_regs *regs)
+{
+}
+
 static inline void kuap_check_amr(void)
 {
 }

arch/powerpc/include/asm/hw_irq.h

@@ -52,6 +52,7 @@
 #ifndef __ASSEMBLY__
 
 extern void replay_system_reset(void);
+extern void replay_soft_interrupts(void);
 
 extern void timer_interrupt(struct pt_regs *);
 extern void timer_broadcast_interrupt(void);

arch/powerpc/include/asm/switch_to.h

@@ -23,7 +23,13 @@ extern void switch_booke_debug_regs(struct debug_reg *new_debug);
 
 extern int emulate_altivec(struct pt_regs *);
 
+#ifdef CONFIG_PPC_BOOK3S_64
 void restore_math(struct pt_regs *regs);
+#else
+static inline void restore_math(struct pt_regs *regs)
+{
+}
+#endif
 
 void restore_tm_state(struct pt_regs *regs);
 

arch/powerpc/kernel/entry_64.S

@@ -16,6 +16,7 @@
 
 #include <linux/errno.h>
 #include <linux/err.h>
+#include <asm/cache.h>
 #include <asm/unistd.h>
 #include <asm/processor.h>
 #include <asm/page.h>
@@ -228,6 +229,7 @@ _GLOBAL(ret_from_kernel_thread)
 	li	r3,0
 	b	.Lsyscall_exit
 
+#ifdef CONFIG_PPC_BOOK3E
 /* Save non-volatile GPRs, if not already saved. */
 _GLOBAL(save_nvgprs)
 	ld	r11,_TRAP(r1)
@@ -238,6 +240,7 @@ _GLOBAL(save_nvgprs)
 	std	r0,_TRAP(r1)
 	blr
 _ASM_NOKPROBE_SYMBOL(save_nvgprs);
+#endif
 
 #ifdef CONFIG_PPC_BOOK3S_64
 
@@ -301,7 +304,7 @@ flush_count_cache:
  * state of one is saved on its kernel stack.  Then the state
  * of the other is restored from its kernel stack.  The memory
  * management hardware is updated to the second process's state.
- * Finally, we can return to the second process, via ret_from_except.
+ * Finally, we can return to the second process, via interrupt_return.
  * On entry, r3 points to the THREAD for the current task, r4
  * points to the THREAD for the new task.
  *
@@ -453,408 +456,152 @@ END_FTR_SECTION_IFCLR(CPU_FTR_ARCH_207S)
 	addi	r1,r1,SWITCH_FRAME_SIZE
 	blr
 
-	.align	7
-_GLOBAL(ret_from_except)
-	ld	r11,_TRAP(r1)
-	andi.	r0,r11,1
-	bne	ret_from_except_lite
-	REST_NVGPRS(r1)
-
-_GLOBAL(ret_from_except_lite)
+#ifdef CONFIG_PPC_BOOK3S
 	/*
-	 * Disable interrupts so that current_thread_info()->flags
-	 * can't change between when we test it and when we return
-	 * from the interrupt.
-	 */
-#ifdef CONFIG_PPC_BOOK3E
-	wrteei	0
-#else
-	li	r10,MSR_RI
-	mtmsrd	r10,1		  /* Update machine state */
-#endif /* CONFIG_PPC_BOOK3E */
+	 * If MSR EE/RI was never enabled, IRQs not reconciled, NVGPRs not
+	 * touched, AMR not set, no exit work created, then this can be used.
+	 */
+	.balign IFETCH_ALIGN_BYTES
+	.globl fast_interrupt_return
+fast_interrupt_return:
+_ASM_NOKPROBE_SYMBOL(fast_interrupt_return)
+	ld	r4,_MSR(r1)
+	andi.	r0,r4,MSR_PR
+	bne	.Lfast_user_interrupt_return
+	andi.	r0,r4,MSR_RI
+	li	r3,0 /* 0 return value, no EMULATE_STACK_STORE */
+	bne+	.Lfast_kernel_interrupt_return
+	addi	r3,r1,STACK_FRAME_OVERHEAD
+	bl	unrecoverable_exception
+	b	. /* should not get here */
 
-	ld	r9, PACA_THREAD_INFO(r13)
-	ld	r3,_MSR(r1)
-#ifdef CONFIG_PPC_BOOK3E
-	ld	r10,PACACURRENT(r13)
-#endif /* CONFIG_PPC_BOOK3E */
-	ld	r4,TI_FLAGS(r9)
-	andi.	r3,r3,MSR_PR
-	beq	resume_kernel
-#ifdef CONFIG_PPC_BOOK3E
-	lwz	r3,(THREAD+THREAD_DBCR0)(r10)
-#endif /* CONFIG_PPC_BOOK3E */
+	.balign IFETCH_ALIGN_BYTES
+	.globl interrupt_return
+interrupt_return:
+_ASM_NOKPROBE_SYMBOL(interrupt_return)
+	REST_NVGPRS(r1)
 
-	/* Check current_thread_info()->flags */
-	andi.	r0,r4,_TIF_USER_WORK_MASK
-	bne	1f
-#ifdef CONFIG_PPC_BOOK3E
-	/*
-	 * Check to see if the dbcr0 register is set up to debug.
-	 * Use the internal debug mode bit to do this.
-	 */
-	andis.	r0,r3,DBCR0_IDM@h
-	beq	restore
-	mfmsr	r0
-	rlwinm	r0,r0,0,~MSR_DE	/* Clear MSR.DE */
-	mtmsr	r0
-	mtspr	SPRN_DBCR0,r3
-	li	r10, -1
-	mtspr	SPRN_DBSR,r10
-	b	restore
-#else
-	addi	r3,r1,STACK_FRAME_OVERHEAD
-	bl	restore_math
-	b	restore
-#endif
-1:	andi.	r0,r4,_TIF_NEED_RESCHED
-	beq	2f
-	bl	restore_interrupts
-	SCHEDULE_USER
-	b	ret_from_except_lite
-2:
-#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
-	andi.	r0,r4,_TIF_USER_WORK_MASK & ~_TIF_RESTORE_TM
-	bne	3f		/* only restore TM if nothing else to do */
+	.balign IFETCH_ALIGN_BYTES
+	.globl interrupt_return_lite
+interrupt_return_lite:
+_ASM_NOKPROBE_SYMBOL(interrupt_return_lite)
+	ld	r4,_MSR(r1)
+	andi.	r0,r4,MSR_PR
+	beq	.Lkernel_interrupt_return
 	addi	r3,r1,STACK_FRAME_OVERHEAD
-	bl	restore_tm_state
-	b	restore
-3:
-#endif
-	bl	save_nvgprs
-	/*
-	 * Use a non volatile GPR to save and restore our thread_info flags
-	 * across the call to restore_interrupts.
-	 */
-	mr	r30,r4
-	bl	restore_interrupts
-	mr	r4,r30
-	addi	r3,r1,STACK_FRAME_OVERHEAD
-	bl	do_notify_resume
-	b	ret_from_except
-
-resume_kernel:
-	/* check current_thread_info, _TIF_EMULATE_STACK_STORE */
-	andis.	r8,r4,_TIF_EMULATE_STACK_STORE@h
-	beq+	1f
+	bl	interrupt_exit_user_prepare
+	cmpdi	r3,0
+	bne-	.Lrestore_nvgprs
 
-	addi	r8,r1,INT_FRAME_SIZE	/* Get the kprobed function entry */
+.Lfast_user_interrupt_return:
+	ld	r11,_NIP(r1)
+	ld	r12,_MSR(r1)
+BEGIN_FTR_SECTION
+	ld	r10,_PPR(r1)
+	mtspr	SPRN_PPR,r10
+END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
+	mtspr	SPRN_SRR0,r11
+	mtspr	SPRN_SRR1,r12
 
-	ld	r3,GPR1(r1)
-	subi	r3,r3,INT_FRAME_SIZE	/* dst: Allocate a trampoline exception frame */
-	mr	r4,r1			/* src:  current exception frame */
-	mr	r1,r3			/* Reroute the trampoline frame to r1 */
+BEGIN_FTR_SECTION
+	stdcx.	r0,0,r1		/* to clear the reservation */
+FTR_SECTION_ELSE
+	ldarx	r0,0,r1
+ALT_FTR_SECTION_END_IFCLR(CPU_FTR_STCX_CHECKS_ADDRESS)
 
-	/* Copy from the original to the trampoline. */
-	li	r5,INT_FRAME_SIZE/8	/* size: INT_FRAME_SIZE */
-	li	r6,0			/* start offset: 0 */
-	mtctr	r5
-2:	ldx	r0,r6,r4
-	stdx	r0,r6,r3
-	addi	r6,r6,8
-	bdnz	2b
-
-	/* Do real store operation to complete stdu */
-	ld	r5,GPR1(r1)
-	std	r8,0(r5)
-
-	/* Clear _TIF_EMULATE_STACK_STORE flag */
-	lis	r11,_TIF_EMULATE_STACK_STORE@h
-	addi	r5,r9,TI_FLAGS
-0:	ldarx	r4,0,r5
-	andc	r4,r4,r11
-	stdcx.	r4,0,r5
-	bne-	0b
-1:
-
-#ifdef CONFIG_PREEMPTION
-	/* Check if we need to preempt */
-	andi.	r0,r4,_TIF_NEED_RESCHED
-	beq+	restore
-	/* Check that preempt_count() == 0 and interrupts are enabled */
-	lwz	r8,TI_PREEMPT(r9)
-	cmpwi	cr0,r8,0
-	bne	restore
-	ld	r0,SOFTE(r1)
-	andi.	r0,r0,IRQS_DISABLED
-	bne	restore
+	ld	r3,_CCR(r1)
+	ld	r4,_LINK(r1)
+	ld	r5,_CTR(r1)
+	ld	r6,_XER(r1)
+	li	r0,0
 
-	/*
-	 * Here we are preempting the current task. We want to make
-	 * sure we are soft-disabled first and reconcile irq state.
-	 */
-	RECONCILE_IRQ_STATE(r3,r4)
-	bl	preempt_schedule_irq
+	REST_4GPRS(7, r1)
+	REST_2GPRS(11, r1)
+	REST_GPR(13, r1)
 
-	/*
-	 * arch_local_irq_restore() from preempt_schedule_irq above may
-	 * enable hard interrupt but we really should disable interrupts
-	 * when we return from the interrupt, and so that we don't get
-	 * interrupted after loading SRR0/1.
-	 */
-#ifdef CONFIG_PPC_BOOK3E
-	wrteei	0
-#else
-	li	r10,MSR_RI
-	mtmsrd	r10,1		  /* Update machine state */
-#endif /* CONFIG_PPC_BOOK3E */
-#endif /* CONFIG_PREEMPTION */
+	mtcr	r3
+	mtlr	r4
+	mtctr	r5
+	mtspr	SPRN_XER,r6
 
-	.globl	fast_exc_return_irq
-fast_exc_return_irq:
-restore:
-	/*
-	 * This is the main kernel exit path. First we check if we
-	 * are about to re-enable interrupts
-	 */
-	ld	r5,SOFTE(r1)
-	lbz	r6,PACAIRQSOFTMASK(r13)
-	andi.	r5,r5,IRQS_DISABLED
-	bne	.Lrestore_irq_off
+	REST_4GPRS(2, r1)
+	REST_GPR(6, r1)
+	REST_GPR(0, r1)
+	REST_GPR(1, r1)
+	RFI_TO_USER
+	b	.	/* prevent speculative execution */
 
-	/* We are enabling, were we already enabled ? Yes, just return */
-	andi.	r6,r6,IRQS_DISABLED
-	beq	cr0,.Ldo_restore
+.Lrestore_nvgprs:
+	REST_NVGPRS(r1)
+	b	.Lfast_user_interrupt_return
 
-	/*
-	 * We are about to soft-enable interrupts (we are hard disabled
-	 * at this point). We check if there's anything that needs to
-	 * be replayed first.
-	 */
-	lbz	r0,PACAIRQHAPPENED(r13)
-	cmpwi	cr0,r0,0
-	bne-	.Lrestore_check_irq_replay
+	.balign IFETCH_ALIGN_BYTES
+.Lkernel_interrupt_return:
+	addi	r3,r1,STACK_FRAME_OVERHEAD
+	bl	interrupt_exit_kernel_prepare
 
-	/*
-	 * Get here when nothing happened while soft-disabled, just
-	 * soft-enable and move-on. We will hard-enable as a side
-	 * effect of rfi
-	 */
-.Lrestore_no_replay:
-	TRACE_ENABLE_INTS
-	li	r0,IRQS_ENABLED
-	stb	r0,PACAIRQSOFTMASK(r13);
+.Lfast_kernel_interrupt_return:
+	cmpdi	cr1,r3,0
+	ld	r11,_NIP(r1)
+	ld	r12,_MSR(r1)
+	mtspr	SPRN_SRR0,r11
+	mtspr	SPRN_SRR1,r12
 
-	/*
-	 * Final return path. BookE is handled in a different file
-	 */
-.Ldo_restore:
-#ifdef CONFIG_PPC_BOOK3E
-	b	exception_return_book3e
-#else
-	/*
-	 * Clear the reservation. If we know the CPU tracks the address of
-	 * the reservation then we can potentially save some cycles and use
-	 * a larx. On POWER6 and POWER7 this is significantly faster.
-	 */
 BEGIN_FTR_SECTION
 	stdcx.	r0,0,r1		/* to clear the reservation */
 FTR_SECTION_ELSE
-	ldarx	r4,0,r1
+	ldarx	r0,0,r1
 ALT_FTR_SECTION_END_IFCLR(CPU_FTR_STCX_CHECKS_ADDRESS)
 
-	/*
-	 * Some code path such as load_up_fpu or altivec return directly
-	 * here. They run entirely hard disabled and do not alter the
-	 * interrupt state. They also don't use lwarx/stwcx. and thus
-	 * are known not to leave dangling reservations.
-	 */
-	.globl	fast_exception_return
-fast_exception_return:
-	ld	r3,_MSR(r1)
+	ld	r3,_LINK(r1)
 	ld	r4,_CTR(r1)
-	ld	r0,_LINK(r1)
-	mtctr	r4
-	mtlr	r0
-	ld	r4,_XER(r1)
-	mtspr	SPRN_XER,r4
-
-	kuap_check_amr r5, r6
-
-	REST_8GPRS(5, r1)
-
-	andi.	r0,r3,MSR_RI
-	beq-	.Lunrecov_restore
-
-	/*
-	 * Clear RI before restoring r13.  If we are returning to
-	 * userspace and we take an exception after restoring r13,
-	 * we end up corrupting the userspace r13 value.
-	 */
-	li	r4,0
-	mtmsrd	r4,1
-
-#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
-	/* TM debug */
-	std	r3, PACATMSCRATCH(r13) /* Stash returned-to MSR */
-#endif
-	/*
-	 * r13 is our per cpu area, only restore it if we are returning to
-	 * userspace the value stored in the stack frame may belong to
-	 * another CPU.
-	 */
-	andi.	r0,r3,MSR_PR
-	beq	1f
-BEGIN_FTR_SECTION
-	/* Restore PPR */
-	ld	r2,_PPR(r1)
-	mtspr	SPRN_PPR,r2
-END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
-	ACCOUNT_CPU_USER_EXIT(r13, r2, r4)
-	REST_GPR(13, r1)
-
-	/*
-	 * 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.
-	 */
-	mtspr	SPRN_SRR1,r3
-
-	ld	r2,_CCR(r1)
-	mtcrf	0xFF,r2
-	ld	r2,_NIP(r1)
-	mtspr	SPRN_SRR0,r2
-
-	ld	r0,GPR0(r1)
-	ld	r2,GPR2(r1)
-	ld	r3,GPR3(r1)
-	ld	r4,GPR4(r1)
-	ld	r1,GPR1(r1)
-	RFI_TO_USER
-	b	.	/* prevent speculative execution */
+	ld	r5,_XER(r1)
+	ld	r6,_CCR(r1)
+	li	r0,0
 
-1:	mtspr	SPRN_SRR1,r3
+	REST_4GPRS(7, r1)
+	REST_2GPRS(11, r1)
 
-	ld	r2,_CCR(r1)
-	mtcrf	0xFF,r2
-	ld	r2,_NIP(r1)
-	mtspr	SPRN_SRR0,r2
+	mtlr	r3
+	mtctr	r4
+	mtspr	SPRN_XER,r5
 
 	/*
 	 * Leaving a stale exception_marker on the stack can confuse
 	 * the reliable stack unwinder later on. Clear it.
 	 */
-	li	r2,0
-	std	r2,STACK_FRAME_OVERHEAD-16(r1)
+	std	r0,STACK_FRAME_OVERHEAD-16(r1)
 
-	ld	r0,GPR0(r1)
-	ld	r2,GPR2(r1)
-	ld	r3,GPR3(r1)
+	REST_4GPRS(2, r1)
 
-	kuap_restore_amr r4
-
-	ld	r4,GPR4(r1)
-	ld	r1,GPR1(r1)
+	bne-	cr1,1f /* emulate stack store */
+	mtcr	r6
+	REST_GPR(6, r1)
+	REST_GPR(0, r1)
+	REST_GPR(1, r1)
 	RFI_TO_KERNEL
 	b	.	/* prevent speculative execution */
 
-#endif /* CONFIG_PPC_BOOK3E */
-
-	/*
-	 * We are returning to a context with interrupts soft disabled.
-	 *
-	 * However, we may also about to hard enable, so we need to
-	 * make sure that in this case, we also clear PACA_IRQ_HARD_DIS
-	 * or that bit can get out of sync and bad things will happen
-	 */
-.Lrestore_irq_off:
-	ld	r3,_MSR(r1)
-	lbz	r7,PACAIRQHAPPENED(r13)
-	andi.	r0,r3,MSR_EE
-	beq	1f
-	rlwinm	r7,r7,0,~PACA_IRQ_HARD_DIS
-	stb	r7,PACAIRQHAPPENED(r13)
-1:
-#if defined(CONFIG_PPC_IRQ_SOFT_MASK_DEBUG) && defined(CONFIG_BUG)
-	/* The interrupt should not have soft enabled. */
-	lbz	r7,PACAIRQSOFTMASK(r13)
-1:	tdeqi	r7,IRQS_ENABLED
-	EMIT_BUG_ENTRY 1b,__FILE__,__LINE__,BUGFLAG_WARNING
-#endif
-	b	.Ldo_restore
-
-	/*
-	 * Something did happen, check if a re-emit is needed
-	 * (this also clears paca->irq_happened)
-	 */
-.Lrestore_check_irq_replay:
-	/* XXX: We could implement a fast path here where we check
-	 * for irq_happened being just 0x01, in which case we can
-	 * clear it and return. That means that we would potentially
-	 * miss a decrementer having wrapped all the way around.
-	 *
-	 * Still, this might be useful for things like hash_page
-	 */
-	bl	__check_irq_replay
-	cmpwi	cr0,r3,0
-	beq	.Lrestore_no_replay
- 
-	/*
-	 * We need to re-emit an interrupt. We do so by re-using our
-	 * existing exception frame. We first change the trap value,
-	 * but we need to ensure we preserve the low nibble of it
-	 */
-	ld	r4,_TRAP(r1)
-	clrldi	r4,r4,60
-	or	r4,r4,r3
-	std	r4,_TRAP(r1)
-
-	/*
-	 * PACA_IRQ_HARD_DIS won't always be set here, so set it now
-	 * to reconcile the IRQ state. Tracing is already accounted for.
-	 */
-	lbz	r4,PACAIRQHAPPENED(r13)
-	ori	r4,r4,PACA_IRQ_HARD_DIS
-	stb	r4,PACAIRQHAPPENED(r13)
-
-	/*
-	 * Then find the right handler and call it. Interrupts are
-	 * still soft-disabled and we keep them that way.
-	*/
-	cmpwi	cr0,r3,0x500
-	bne	1f
-	addi	r3,r1,STACK_FRAME_OVERHEAD;
- 	bl	do_IRQ
-	b	ret_from_except
-1:	cmpwi	cr0,r3,0xf00
-	bne	1f
-	addi	r3,r1,STACK_FRAME_OVERHEAD;
-	bl	performance_monitor_exception
-	b	ret_from_except
-1:	cmpwi	cr0,r3,0xe60
-	bne	1f
-	addi	r3,r1,STACK_FRAME_OVERHEAD;
-	bl	handle_hmi_exception
-	b	ret_from_except
-1:	cmpwi	cr0,r3,0x900
-	bne	1f
-	addi	r3,r1,STACK_FRAME_OVERHEAD;
-	bl	timer_interrupt
-	b	ret_from_except
-#ifdef CONFIG_PPC_DOORBELL
-1:
-#ifdef CONFIG_PPC_BOOK3E
-	cmpwi	cr0,r3,0x280
-#else
-	cmpwi	cr0,r3,0xa00
-#endif /* CONFIG_PPC_BOOK3E */
-	bne	1f
-	addi	r3,r1,STACK_FRAME_OVERHEAD;
-	bl	doorbell_exception
-#endif /* CONFIG_PPC_DOORBELL */
-1:	b	ret_from_except /* What else to do here ? */
- 
-.Lunrecov_restore:
-	addi	r3,r1,STACK_FRAME_OVERHEAD
-	bl	unrecoverable_exception
-	b	.Lunrecov_restore
-
-_ASM_NOKPROBE_SYMBOL(ret_from_except);
-_ASM_NOKPROBE_SYMBOL(ret_from_except_lite);
-_ASM_NOKPROBE_SYMBOL(resume_kernel);
-_ASM_NOKPROBE_SYMBOL(fast_exc_return_irq);
-_ASM_NOKPROBE_SYMBOL(restore);
-_ASM_NOKPROBE_SYMBOL(fast_exception_return);
+1:	/*
+	 * Emulate stack store with update. New r1 value was already calculated
+	 * and updated in our interrupt regs by emulate_loadstore, but we can't
+	 * store the previous value of r1 to the stack before re-loading our
+	 * registers from it, otherwise they could be clobbered.  Use
+	 * PACA_EXGEN as temporary storage to hold the store data, as
+	 * interrupts are disabled here so it won't be clobbered.
+	 */
+	mtcr	r6
+	std	r9,PACA_EXGEN+0(r13)
+	addi	r9,r1,INT_FRAME_SIZE /* get original r1 */
+	REST_GPR(6, r1)
+	REST_GPR(0, r1)
+	REST_GPR(1, r1)
+	std	r9,0(r1) /* perform store component of stdu */
+	ld	r9,PACA_EXGEN+0(r13)
 
+	RFI_TO_KERNEL
+	b	.	/* prevent speculative execution */
+#endif /* CONFIG_PPC_BOOK3S */
 
 #ifdef CONFIG_PPC_RTAS
 /*

arch/powerpc/kernel/exceptions-64e.S

@@ -24,6 +24,7 @@
 #include <asm/kvm_asm.h>
 #include <asm/kvm_booke_hv_asm.h>
 #include <asm/feature-fixups.h>
+#include <asm/context_tracking.h>
 
 /* XXX This will ultimately add space for a special exception save
  *     structure used to save things like SRR0/SRR1, SPRGs, MAS, etc...
@@ -1041,17 +1042,161 @@ alignment_more:
 	bl	alignment_exception
 	b	ret_from_except
 
-/*
- * We branch here from entry_64.S for the last stage of the exception
- * return code path. MSR:EE is expected to be off at that point
- */
-_GLOBAL(exception_return_book3e)
-	b	1f
+	.align	7
+_GLOBAL(ret_from_except)
+	ld	r11,_TRAP(r1)
+	andi.	r0,r11,1
+	bne	ret_from_except_lite
+	REST_NVGPRS(r1)
+
+_GLOBAL(ret_from_except_lite)
+	/*
+	 * Disable interrupts so that current_thread_info()->flags
+	 * can't change between when we test it and when we return
+	 * from the interrupt.
+	 */
+	wrteei	0
+
+	ld	r9, PACA_THREAD_INFO(r13)
+	ld	r3,_MSR(r1)
+	ld	r10,PACACURRENT(r13)
+	ld	r4,TI_FLAGS(r9)
+	andi.	r3,r3,MSR_PR
+	beq	resume_kernel
+	lwz	r3,(THREAD+THREAD_DBCR0)(r10)
+
+	/* Check current_thread_info()->flags */
+	andi.	r0,r4,_TIF_USER_WORK_MASK
+	bne	1f
+	/*
+	 * Check to see if the dbcr0 register is set up to debug.
+	 * Use the internal debug mode bit to do this.
+	 */
+	andis.	r0,r3,DBCR0_IDM@h
+	beq	restore
+	mfmsr	r0
+	rlwinm	r0,r0,0,~MSR_DE	/* Clear MSR.DE */
+	mtmsr	r0
+	mtspr	SPRN_DBCR0,r3
+	li	r10, -1
+	mtspr	SPRN_DBSR,r10
+	b	restore
+1:	andi.	r0,r4,_TIF_NEED_RESCHED
+	beq	2f
+	bl	restore_interrupts
+	SCHEDULE_USER
+	b	ret_from_except_lite
+2:
+	bl	save_nvgprs
+	/*
+	 * Use a non volatile GPR to save and restore our thread_info flags
+	 * across the call to restore_interrupts.
+	 */
+	mr	r30,r4
+	bl	restore_interrupts
+	mr	r4,r30
+	addi	r3,r1,STACK_FRAME_OVERHEAD
+	bl	do_notify_resume
+	b	ret_from_except
+
+resume_kernel:
+	/* check current_thread_info, _TIF_EMULATE_STACK_STORE */
+	andis.	r8,r4,_TIF_EMULATE_STACK_STORE@h
+	beq+	1f
+
+	addi	r8,r1,INT_FRAME_SIZE	/* Get the kprobed function entry */
+
+	ld	r3,GPR1(r1)
+	subi	r3,r3,INT_FRAME_SIZE	/* dst: Allocate a trampoline exception frame */
+	mr	r4,r1			/* src:  current exception frame */
+	mr	r1,r3			/* Reroute the trampoline frame to r1 */
+
+	/* Copy from the original to the trampoline. */
+	li	r5,INT_FRAME_SIZE/8	/* size: INT_FRAME_SIZE */
+	li	r6,0			/* start offset: 0 */
+	mtctr	r5
+2:	ldx	r0,r6,r4
+	stdx	r0,r6,r3
+	addi	r6,r6,8
+	bdnz	2b
+
+	/* Do real store operation to complete stdu */
+	ld	r5,GPR1(r1)
+	std	r8,0(r5)
+
+	/* Clear _TIF_EMULATE_STACK_STORE flag */
+	lis	r11,_TIF_EMULATE_STACK_STORE@h
+	addi	r5,r9,TI_FLAGS
+0:	ldarx	r4,0,r5
+	andc	r4,r4,r11
+	stdcx.	r4,0,r5
+	bne-	0b
+1:
+
+#ifdef CONFIG_PREEMPT
+	/* Check if we need to preempt */
+	andi.	r0,r4,_TIF_NEED_RESCHED
+	beq+	restore
+	/* Check that preempt_count() == 0 and interrupts are enabled */
+	lwz	r8,TI_PREEMPT(r9)
+	cmpwi	cr0,r8,0
+	bne	restore
+	ld	r0,SOFTE(r1)
+	andi.	r0,r0,IRQS_DISABLED
+	bne	restore
+
+	/*
+	 * Here we are preempting the current task. We want to make
+	 * sure we are soft-disabled first and reconcile irq state.
+	 */
+	RECONCILE_IRQ_STATE(r3,r4)
+	bl	preempt_schedule_irq
+
+	/*
+	 * arch_local_irq_restore() from preempt_schedule_irq above may
+	 * enable hard interrupt but we really should disable interrupts
+	 * when we return from the interrupt, and so that we don't get
+	 * interrupted after loading SRR0/1.
+	 */
+	wrteei	0
+#endif /* CONFIG_PREEMPT */
+
+restore:
+	/*
+	 * This is the main kernel exit path. First we check if we
+	 * are about to re-enable interrupts
+	 */
+	ld	r5,SOFTE(r1)
+	lbz	r6,PACAIRQSOFTMASK(r13)
+	andi.	r5,r5,IRQS_DISABLED
+	bne	.Lrestore_irq_off
+
+	/* We are enabling, were we already enabled ? Yes, just return */
+	andi.	r6,r6,IRQS_DISABLED
+	beq	cr0,fast_exception_return
+
+	/*
+	 * We are about to soft-enable interrupts (we are hard disabled
+	 * at this point). We check if there's anything that needs to
+	 * be replayed first.
+	 */
+	lbz	r0,PACAIRQHAPPENED(r13)
+	cmpwi	cr0,r0,0
+	bne-	.Lrestore_check_irq_replay
+
+	/*
+	 * Get here when nothing happened while soft-disabled, just
+	 * soft-enable and move-on. We will hard-enable as a side
+	 * effect of rfi
+	 */
+.Lrestore_no_replay:
+	TRACE_ENABLE_INTS
+	li	r0,IRQS_ENABLED
+	stb	r0,PACAIRQSOFTMASK(r13);
 
 /* This is the return from load_up_fpu fast path which could do with
  * less GPR restores in fact, but for now we have a single return path
  */
-	.globl fast_exception_return
 fast_exception_return:
 	wrteei	0
 1:	mr	r0,r13
@@ -1092,6 +1237,102 @@ fast_exception_return:
 	mfspr	r13,SPRN_SPRG_GEN_SCRATCH
 	rfi
 
+	/*
+	 * We are returning to a context with interrupts soft disabled.
+	 *
+	 * However, we may also about to hard enable, so we need to
+	 * make sure that in this case, we also clear PACA_IRQ_HARD_DIS
+	 * or that bit can get out of sync and bad things will happen
+	 */
+.Lrestore_irq_off:
+	ld	r3,_MSR(r1)
+	lbz	r7,PACAIRQHAPPENED(r13)
+	andi.	r0,r3,MSR_EE
+	beq	1f
+	rlwinm	r7,r7,0,~PACA_IRQ_HARD_DIS
+	stb	r7,PACAIRQHAPPENED(r13)
+1:
+#if defined(CONFIG_PPC_IRQ_SOFT_MASK_DEBUG) && defined(CONFIG_BUG)
+	/* The interrupt should not have soft enabled. */
+	lbz	r7,PACAIRQSOFTMASK(r13)
+1:	tdeqi	r7,IRQS_ENABLED
+	EMIT_BUG_ENTRY 1b,__FILE__,__LINE__,BUGFLAG_WARNING
+#endif
+	b	fast_exception_return
+
+	/*
+	 * Something did happen, check if a re-emit is needed
+	 * (this also clears paca->irq_happened)
+	 */
+.Lrestore_check_irq_replay:
+	/* XXX: We could implement a fast path here where we check
+	 * for irq_happened being just 0x01, in which case we can
+	 * clear it and return. That means that we would potentially
+	 * miss a decrementer having wrapped all the way around.
+	 *
+	 * Still, this might be useful for things like hash_page
+	 */
+	bl	__check_irq_replay
+	cmpwi	cr0,r3,0
+	beq	.Lrestore_no_replay
+
+	/*
+	 * We need to re-emit an interrupt. We do so by re-using our
+	 * existing exception frame. We first change the trap value,
+	 * but we need to ensure we preserve the low nibble of it
+	 */
+	ld	r4,_TRAP(r1)
+	clrldi	r4,r4,60
+	or	r4,r4,r3
+	std	r4,_TRAP(r1)
+
+	/*
+	 * PACA_IRQ_HARD_DIS won't always be set here, so set it now
+	 * to reconcile the IRQ state. Tracing is already accounted for.
+	 */
+	lbz	r4,PACAIRQHAPPENED(r13)
+	ori	r4,r4,PACA_IRQ_HARD_DIS
+	stb	r4,PACAIRQHAPPENED(r13)
+
+	/*
+	 * Then find the right handler and call it. Interrupts are
+	 * still soft-disabled and we keep them that way.
+	*/
+	cmpwi	cr0,r3,0x500
+	bne	1f
+	addi	r3,r1,STACK_FRAME_OVERHEAD;
+	bl	do_IRQ
+	b	ret_from_except
+1:	cmpwi	cr0,r3,0xf00
+	bne	1f
+	addi	r3,r1,STACK_FRAME_OVERHEAD;
+	bl	performance_monitor_exception
+	b	ret_from_except
+1:	cmpwi	cr0,r3,0xe60
+	bne	1f
+	addi	r3,r1,STACK_FRAME_OVERHEAD;
+	bl	handle_hmi_exception
+	b	ret_from_except
+1:	cmpwi	cr0,r3,0x900
+	bne	1f
+	addi	r3,r1,STACK_FRAME_OVERHEAD;
+	bl	timer_interrupt
+	b	ret_from_except
+#ifdef CONFIG_PPC_DOORBELL
+1:
+	cmpwi	cr0,r3,0x280
+	bne	1f
+	addi	r3,r1,STACK_FRAME_OVERHEAD;
+	bl	doorbell_exception
+#endif /* CONFIG_PPC_DOORBELL */
+1:	b	ret_from_except /* What else to do here ? */
+
+_ASM_NOKPROBE_SYMBOL(ret_from_except);
+_ASM_NOKPROBE_SYMBOL(ret_from_except_lite);
+_ASM_NOKPROBE_SYMBOL(resume_kernel);
+_ASM_NOKPROBE_SYMBOL(restore);
+_ASM_NOKPROBE_SYMBOL(fast_exception_return);
+
 /*
  * Trampolines used when spotting a bad kernel stack pointer in
  * the exception entry code.

arch/powerpc/kernel/exceptions-64s.S

@@ -589,6 +589,8 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
 	std	r10,GPR12(r1)
 	std	r11,GPR13(r1)
 
+	SAVE_NVGPRS(r1)
+
 	.if IDAR
 	.if IISIDE
 	ld	r10,_NIP(r1)
@@ -625,7 +627,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_CFAR)
 	mfspr	r11,SPRN_XER		/* save XER in stackframe	*/
 	std	r10,SOFTE(r1)
 	std	r11,_XER(r1)
-	li	r9,(IVEC)+1
+	li	r9,IVEC
 	std	r9,_TRAP(r1)		/* set trap number		*/
 	li	r10,0
 	ld	r11,exception_marker@toc(r2)
@@ -932,7 +934,6 @@ EXC_COMMON_BEGIN(system_reset_common)
 	ld	r1,PACA_NMI_EMERG_SP(r13)
 	subi	r1,r1,INT_FRAME_SIZE
 	__GEN_COMMON_BODY system_reset
-	bl	save_nvgprs
 	/*
 	 * Set IRQS_ALL_DISABLED unconditionally so irqs_disabled() does
 	 * the right thing. We do not want to reconcile because that goes
@@ -1115,7 +1116,6 @@ END_FTR_SECTION_IFSET(CPU_FTR_HVMODE)
 	li	r10,MSR_RI
 	mtmsrd	r10,1
 
-	bl	save_nvgprs
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 	bl	machine_check_early
 	std	r3,RESULT(r1)	/* Save result */
@@ -1208,10 +1208,9 @@ EXC_COMMON_BEGIN(machine_check_common)
 	/* Enable MSR_RI when finished with PACA_EXMC */
 	li	r10,MSR_RI
 	mtmsrd 	r10,1
-	bl	save_nvgprs
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 	bl	machine_check_exception
-	b	ret_from_except
+	b	interrupt_return
 
 	GEN_KVM machine_check
 
@@ -1378,20 +1377,19 @@ BEGIN_MMU_FTR_SECTION
 	bl	do_slb_fault
 	cmpdi	r3,0
 	bne-	1f
-	b	fast_exception_return
+	b	fast_interrupt_return
 1:	/* Error case */
 MMU_FTR_SECTION_ELSE
 	/* Radix case, access is outside page table range */
 	li	r3,-EFAULT
 ALT_MMU_FTR_SECTION_END_IFCLR(MMU_FTR_TYPE_RADIX)
 	std	r3,RESULT(r1)
-	bl	save_nvgprs
 	RECONCILE_IRQ_STATE(r10, r11)
 	ld	r4,_DAR(r1)
 	ld	r5,RESULT(r1)
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 	bl	do_bad_slb_fault
-	b	ret_from_except
+	b	interrupt_return
 
 	GEN_KVM data_access_slb
 
@@ -1471,20 +1469,19 @@ BEGIN_MMU_FTR_SECTION
 	bl	do_slb_fault
 	cmpdi	r3,0
 	bne-	1f
-	b	fast_exception_return
+	b	fast_interrupt_return
 1:	/* Error case */
 MMU_FTR_SECTION_ELSE
 	/* Radix case, access is outside page table range */
 	li	r3,-EFAULT
 ALT_MMU_FTR_SECTION_END_IFCLR(MMU_FTR_TYPE_RADIX)
 	std	r3,RESULT(r1)
-	bl	save_nvgprs
 	RECONCILE_IRQ_STATE(r10, r11)
 	ld	r4,_DAR(r1)
 	ld	r5,RESULT(r1)
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 	bl	do_bad_slb_fault
-	b	ret_from_except
+	b	interrupt_return
 
 	GEN_KVM instruction_access_slb
 
@@ -1532,7 +1529,7 @@ EXC_COMMON_BEGIN(hardware_interrupt_common)
 	RUNLATCH_ON
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 	bl	do_IRQ
-	b	ret_from_except_lite
+	b	interrupt_return_lite
 
 	GEN_KVM hardware_interrupt
 
@@ -1558,10 +1555,9 @@ EXC_VIRT_BEGIN(alignment, 0x4600, 0x100)
 EXC_VIRT_END(alignment, 0x4600, 0x100)
 EXC_COMMON_BEGIN(alignment_common)
 	GEN_COMMON alignment
-	bl	save_nvgprs
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 	bl	alignment_exception
-	b	ret_from_except
+	b	interrupt_return
 
 	GEN_KVM alignment
 
@@ -1622,10 +1618,9 @@ EXC_COMMON_BEGIN(program_check_common)
 	__ISTACK(program_check)=1
 	__GEN_COMMON_BODY program_check
 3:
-	bl	save_nvgprs
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 	bl	program_check_exception
-	b	ret_from_except
+	b	interrupt_return
 
 	GEN_KVM program_check
 
@@ -1656,7 +1651,6 @@ EXC_VIRT_END(fp_unavailable, 0x4800, 0x100)
 EXC_COMMON_BEGIN(fp_unavailable_common)
 	GEN_COMMON fp_unavailable
 	bne	1f			/* if from user, just load it up */
-	bl	save_nvgprs
 	RECONCILE_IRQ_STATE(r10, r11)
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 	bl	kernel_fp_unavailable_exception
@@ -1673,14 +1667,13 @@ BEGIN_FTR_SECTION
 END_FTR_SECTION_IFSET(CPU_FTR_TM)
 #endif
 	bl	load_up_fpu
-	b	fast_exception_return
+	b	fast_interrupt_return
 #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
 2:	/* User process was in a transaction */
-	bl	save_nvgprs
 	RECONCILE_IRQ_STATE(r10, r11)
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 	bl	fp_unavailable_tm
-	b	ret_from_except
+	b	interrupt_return
 #endif
 
 	GEN_KVM fp_unavailable
@@ -1723,7 +1716,7 @@ EXC_COMMON_BEGIN(decrementer_common)
 	RUNLATCH_ON
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 	bl	timer_interrupt
-	b	ret_from_except_lite
+	b	interrupt_return_lite
 
 	GEN_KVM decrementer
 
@@ -1814,7 +1807,7 @@ EXC_COMMON_BEGIN(doorbell_super_common)
 #else
 	bl	unknown_exception
 #endif
-	b	ret_from_except_lite
+	b	interrupt_return_lite
 
 	GEN_KVM doorbell_super
 
@@ -1986,10 +1979,9 @@ EXC_VIRT_BEGIN(single_step, 0x4d00, 0x100)
 EXC_VIRT_END(single_step, 0x4d00, 0x100)
 EXC_COMMON_BEGIN(single_step_common)
 	GEN_COMMON single_step
-	bl	save_nvgprs
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 	bl	single_step_exception
-	b	ret_from_except
+	b	interrupt_return
 
 	GEN_KVM single_step
 
@@ -2024,7 +2016,6 @@ EXC_VIRT_BEGIN(h_data_storage, 0x4e00, 0x20)
 EXC_VIRT_END(h_data_storage, 0x4e00, 0x20)
 EXC_COMMON_BEGIN(h_data_storage_common)
 	GEN_COMMON h_data_storage
-	bl      save_nvgprs
 	addi    r3,r1,STACK_FRAME_OVERHEAD
 BEGIN_MMU_FTR_SECTION
 	ld	r4,_DAR(r1)
@@ -2033,7 +2024,7 @@ BEGIN_MMU_FTR_SECTION
 MMU_FTR_SECTION_ELSE
 	bl      unknown_exception
 ALT_MMU_FTR_SECTION_END_IFSET(MMU_FTR_TYPE_RADIX)
-	b       ret_from_except
+	b       interrupt_return
 
 	GEN_KVM h_data_storage
 
@@ -2058,10 +2049,9 @@ EXC_VIRT_BEGIN(h_instr_storage, 0x4e20, 0x20)
 EXC_VIRT_END(h_instr_storage, 0x4e20, 0x20)
 EXC_COMMON_BEGIN(h_instr_storage_common)
 	GEN_COMMON h_instr_storage
-	bl	save_nvgprs
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 	bl	unknown_exception
-	b	ret_from_except
+	b	interrupt_return
 
 	GEN_KVM h_instr_storage
 
@@ -2084,10 +2074,9 @@ EXC_VIRT_BEGIN(emulation_assist, 0x4e40, 0x20)
 EXC_VIRT_END(emulation_assist, 0x4e40, 0x20)
 EXC_COMMON_BEGIN(emulation_assist_common)
 	GEN_COMMON emulation_assist
-	bl	save_nvgprs
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 	bl	emulation_assist_interrupt
-	b	ret_from_except
+	b	interrupt_return
 
 	GEN_KVM emulation_assist
 
@@ -2169,10 +2158,9 @@ EXC_COMMON_BEGIN(hmi_exception_common)
 	GEN_COMMON hmi_exception
 	FINISH_NAP
 	RUNLATCH_ON
-	bl	save_nvgprs
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 	bl	handle_hmi_exception
-	b	ret_from_except
+	b	interrupt_return
 
 	GEN_KVM hmi_exception
 
@@ -2206,7 +2194,7 @@ EXC_COMMON_BEGIN(h_doorbell_common)
 #else
 	bl	unknown_exception
 #endif
-	b	ret_from_except_lite
+	b	interrupt_return_lite
 
 	GEN_KVM h_doorbell
 
@@ -2236,7 +2224,7 @@ EXC_COMMON_BEGIN(h_virt_irq_common)
 	RUNLATCH_ON
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 	bl	do_IRQ
-	b	ret_from_except_lite
+	b	interrupt_return_lite
 
 	GEN_KVM h_virt_irq
 
@@ -2283,7 +2271,7 @@ EXC_COMMON_BEGIN(performance_monitor_common)
 	RUNLATCH_ON
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 	bl	performance_monitor_exception
-	b	ret_from_except_lite
+	b	interrupt_return_lite
 
 	GEN_KVM performance_monitor
 
@@ -2323,23 +2311,21 @@ BEGIN_FTR_SECTION
   END_FTR_SECTION_NESTED(CPU_FTR_TM, CPU_FTR_TM, 69)
 #endif
 	bl	load_up_altivec
-	b	fast_exception_return
+	b	fast_interrupt_return
 #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
 2:	/* User process was in a transaction */
-	bl	save_nvgprs
 	RECONCILE_IRQ_STATE(r10, r11)
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 	bl	altivec_unavailable_tm
-	b	ret_from_except
+	b	interrupt_return
 #endif
 1:
 END_FTR_SECTION_IFSET(CPU_FTR_ALTIVEC)
 #endif
-	bl	save_nvgprs
 	RECONCILE_IRQ_STATE(r10, r11)
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 	bl	altivec_unavailable_exception
-	b	ret_from_except
+	b	interrupt_return
 
 	GEN_KVM altivec_unavailable
 
@@ -2381,20 +2367,18 @@ BEGIN_FTR_SECTION
 	b	load_up_vsx
 #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
 2:	/* User process was in a transaction */
-	bl	save_nvgprs
 	RECONCILE_IRQ_STATE(r10, r11)
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 	bl	vsx_unavailable_tm
-	b	ret_from_except
+	b	interrupt_return
 #endif
 1:
 END_FTR_SECTION_IFSET(CPU_FTR_VSX)
 #endif
-	bl	save_nvgprs
 	RECONCILE_IRQ_STATE(r10, r11)
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 	bl	vsx_unavailable_exception
-	b	ret_from_except
+	b	interrupt_return
 
 	GEN_KVM vsx_unavailable
 
@@ -2421,10 +2405,9 @@ EXC_VIRT_BEGIN(facility_unavailable, 0x4f60, 0x20)
 EXC_VIRT_END(facility_unavailable, 0x4f60, 0x20)
 EXC_COMMON_BEGIN(facility_unavailable_common)
 	GEN_COMMON facility_unavailable
-	bl	save_nvgprs
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 	bl	facility_unavailable_exception
-	b	ret_from_except
+	b	interrupt_return
 
 	GEN_KVM facility_unavailable
 
@@ -2451,10 +2434,9 @@ EXC_VIRT_BEGIN(h_facility_unavailable, 0x4f80, 0x20)
 EXC_VIRT_END(h_facility_unavailable, 0x4f80, 0x20)
 EXC_COMMON_BEGIN(h_facility_unavailable_common)
 	GEN_COMMON h_facility_unavailable
-	bl	save_nvgprs
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 	bl	facility_unavailable_exception
-	b	ret_from_except
+	b	interrupt_return
 
 	GEN_KVM h_facility_unavailable
 
@@ -2485,10 +2467,9 @@ EXC_REAL_END(cbe_system_error, 0x1200, 0x100)
 EXC_VIRT_NONE(0x5200, 0x100)
 EXC_COMMON_BEGIN(cbe_system_error_common)
 	GEN_COMMON cbe_system_error
-	bl	save_nvgprs
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 	bl	cbe_system_error_exception
-	b	ret_from_except
+	b	interrupt_return
 
 	GEN_KVM cbe_system_error
 
@@ -2514,10 +2495,9 @@ EXC_VIRT_BEGIN(instruction_breakpoint, 0x5300, 0x100)
 EXC_VIRT_END(instruction_breakpoint, 0x5300, 0x100)
 EXC_COMMON_BEGIN(instruction_breakpoint_common)
 	GEN_COMMON instruction_breakpoint
-	bl	save_nvgprs
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 	bl	instruction_breakpoint_exception
-	b	ret_from_except
+	b	interrupt_return
 
 	GEN_KVM instruction_breakpoint
 
@@ -2637,10 +2617,9 @@ END_FTR_SECTION_IFSET(CPU_FTR_CFAR)
 
 EXC_COMMON_BEGIN(denorm_exception_common)
 	GEN_COMMON denorm_exception
-	bl	save_nvgprs
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 	bl	unknown_exception
-	b	ret_from_except
+	b	interrupt_return
 
 	GEN_KVM denorm_exception
 
@@ -2659,10 +2638,9 @@ EXC_REAL_END(cbe_maintenance, 0x1600, 0x100)
 EXC_VIRT_NONE(0x5600, 0x100)
 EXC_COMMON_BEGIN(cbe_maintenance_common)
 	GEN_COMMON cbe_maintenance
-	bl	save_nvgprs
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 	bl	cbe_maintenance_exception
-	b	ret_from_except
+	b	interrupt_return
 
 	GEN_KVM cbe_maintenance
 
@@ -2687,14 +2665,13 @@ EXC_VIRT_BEGIN(altivec_assist, 0x5700, 0x100)
 EXC_VIRT_END(altivec_assist, 0x5700, 0x100)
 EXC_COMMON_BEGIN(altivec_assist_common)
 	GEN_COMMON altivec_assist
-	bl	save_nvgprs
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 #ifdef CONFIG_ALTIVEC
 	bl	altivec_assist_exception
 #else
 	bl	unknown_exception
 #endif
-	b	ret_from_except
+	b	interrupt_return
 
 	GEN_KVM altivec_assist
 
@@ -2713,10 +2690,9 @@ EXC_REAL_END(cbe_thermal, 0x1800, 0x100)
 EXC_VIRT_NONE(0x5800, 0x100)
 EXC_COMMON_BEGIN(cbe_thermal_common)
 	GEN_COMMON cbe_thermal
-	bl	save_nvgprs
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 	bl	cbe_thermal_exception
-	b	ret_from_except
+	b	interrupt_return
 
 	GEN_KVM cbe_thermal
 
@@ -2749,7 +2725,6 @@ EXC_COMMON_BEGIN(soft_nmi_common)
 	ld	r1,PACAEMERGSP(r13)
 	subi	r1,r1,INT_FRAME_SIZE
 	__GEN_COMMON_BODY soft_nmi
-	bl	save_nvgprs
 
 	/*
 	 * Set IRQS_ALL_DISABLED and save PACAIRQHAPPENED (see
@@ -3082,7 +3057,7 @@ do_hash_page:
         cmpdi	r3,0			/* see if __hash_page succeeded */
 
 	/* Success */
-	beq	fast_exc_return_irq	/* Return from exception on success */
+	beq	interrupt_return_lite	/* Return from exception on success */
 
 	/* Error */
 	blt-	13f
@@ -3099,17 +3074,15 @@ handle_page_fault:
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 	bl	do_page_fault
 	cmpdi	r3,0
-	beq+	ret_from_except_lite
-	bl	save_nvgprs
+	beq+	interrupt_return_lite
 	mr	r5,r3
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 	ld	r4,_DAR(r1)
 	bl	bad_page_fault
-	b	ret_from_except
+	b	interrupt_return
 
 /* We have a data breakpoint exception - handle it */
 handle_dabr_fault:
-	bl	save_nvgprs
 	ld      r4,_DAR(r1)
 	ld      r5,_DSISR(r1)
 	addi    r3,r1,STACK_FRAME_OVERHEAD
@@ -3117,21 +3090,20 @@ handle_dabr_fault:
 	/*
 	 * do_break() may have changed the NV GPRS while handling a breakpoint.
 	 * If so, we need to restore them with their updated values. Don't use
-	 * ret_from_except_lite here.
+	 * interrupt_return_lite here.
 	 */
-	b       ret_from_except
+	b       interrupt_return
 
 
 #ifdef CONFIG_PPC_BOOK3S_64
 /* We have a page fault that hash_page could handle but HV refused
  * the PTE insertion
  */
-13:	bl	save_nvgprs
-	mr	r5,r3
+13:	mr	r5,r3
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 	ld	r4,_DAR(r1)
 	bl	low_hash_fault
-	b	ret_from_except
+	b	interrupt_return
 #endif
 
 /*
@@ -3141,11 +3113,10 @@ handle_dabr_fault:
  * were soft-disabled.  We want to invoke the exception handler for
  * the access, or panic if there isn't a handler.
  */
-77:	bl	save_nvgprs
-	addi	r3,r1,STACK_FRAME_OVERHEAD
+77:	addi	r3,r1,STACK_FRAME_OVERHEAD
 	li	r5,SIGSEGV
 	bl	bad_page_fault
-	b	ret_from_except
+	b	interrupt_return
 
 /*
  * When doorbell is triggered from system reset wakeup, the message is

arch/powerpc/kernel/irq.c

@@ -110,6 +110,8 @@ static inline notrace int decrementer_check_overflow(void)
 	return now >= *next_tb;
 }
 
+#ifdef CONFIG_PPC_BOOK3E
+
 /* This is called whenever we are re-enabling interrupts
  * and returns either 0 (nothing to do) or 500/900/280/a00/e80 if
  * there's an EE, DEC or DBELL to generate.
@@ -169,41 +171,16 @@ notrace unsigned int __check_irq_replay(void)
 		}
 	}
 
-	/*
-	 * Force the delivery of pending soft-disabled interrupts on PS3.
-	 * Any HV call will have this side effect.
-	 */
-	if (firmware_has_feature(FW_FEATURE_PS3_LV1)) {
-		u64 tmp, tmp2;
-		lv1_get_version_info(&tmp, &tmp2);
-	}
-
-	/*
-	 * Check if an hypervisor Maintenance interrupt happened.
-	 * This is a higher priority interrupt than the others, so
-	 * replay it first.
-	 */
-	if (happened & PACA_IRQ_HMI) {
-		local_paca->irq_happened &= ~PACA_IRQ_HMI;
-		return 0xe60;
-	}
-
 	if (happened & PACA_IRQ_DEC) {
 		local_paca->irq_happened &= ~PACA_IRQ_DEC;
 		return 0x900;
 	}
 
-	if (happened & PACA_IRQ_PMI) {
-		local_paca->irq_happened &= ~PACA_IRQ_PMI;
-		return 0xf00;
-	}
-
 	if (happened & PACA_IRQ_EE) {
 		local_paca->irq_happened &= ~PACA_IRQ_EE;
 		return 0x500;
 	}
 
-#ifdef CONFIG_PPC_BOOK3E
 	/*
 	 * Check if an EPR external interrupt happened this bit is typically
 	 * set if we need to handle another "edge" interrupt from within the
@@ -218,20 +195,15 @@ notrace unsigned int __check_irq_replay(void)
 		local_paca->irq_happened &= ~PACA_IRQ_DBELL;
 		return 0x280;
 	}
-#else
-	if (happened & PACA_IRQ_DBELL) {
-		local_paca->irq_happened &= ~PACA_IRQ_DBELL;
-		return 0xa00;
-	}
-#endif /* CONFIG_PPC_BOOK3E */
 
 	/* There should be nothing left ! */
 	BUG_ON(local_paca->irq_happened != 0);
 
 	return 0;
 }
+#endif /* CONFIG_PPC_BOOK3E */
 
-static void replay_soft_interrupts(void)
+void replay_soft_interrupts(void)
 {
 	/*
 	 * We use local_paca rather than get_paca() to avoid all

arch/powerpc/kernel/process.c

@@ -236,23 +236,9 @@ void enable_kernel_fp(void)
 	}
 }
 EXPORT_SYMBOL(enable_kernel_fp);
-
-static int restore_fp(struct task_struct *tsk)
-{
-	if (tsk->thread.load_fp) {
-		load_fp_state(&current->thread.fp_state);
-		current->thread.load_fp++;
-		return 1;
-	}
-	return 0;
-}
-#else
-static int restore_fp(struct task_struct *tsk) { return 0; }
 #endif /* CONFIG_PPC_FPU */
 
 #ifdef CONFIG_ALTIVEC
-#define loadvec(thr) ((thr).load_vec)
-
 static void __giveup_altivec(struct task_struct *tsk)
 {
 	unsigned long msr;
@@ -318,21 +304,6 @@ void flush_altivec_to_thread(struct task_struct *tsk)
 	}
 }
 EXPORT_SYMBOL_GPL(flush_altivec_to_thread);
-
-static int restore_altivec(struct task_struct *tsk)
-{
-	if (cpu_has_feature(CPU_FTR_ALTIVEC) && (tsk->thread.load_vec)) {
-		load_vr_state(&tsk->thread.vr_state);
-		tsk->thread.used_vr = 1;
-		tsk->thread.load_vec++;
-
-		return 1;
-	}
-	return 0;
-}
-#else
-#define loadvec(thr) 0
-static inline int restore_altivec(struct task_struct *tsk) { return 0; }
 #endif /* CONFIG_ALTIVEC */
 
 #ifdef CONFIG_VSX
@@ -400,18 +371,6 @@ void flush_vsx_to_thread(struct task_struct *tsk)
 	}
 }
 EXPORT_SYMBOL_GPL(flush_vsx_to_thread);
-
-static int restore_vsx(struct task_struct *tsk)
-{
-	if (cpu_has_feature(CPU_FTR_VSX)) {
-		tsk->thread.used_vsr = 1;
-		return 1;
-	}
-
-	return 0;
-}
-#else
-static inline int restore_vsx(struct task_struct *tsk) { return 0; }
 #endif /* CONFIG_VSX */
 
 #ifdef CONFIG_SPE
@@ -511,6 +470,53 @@ void giveup_all(struct task_struct *tsk)
 }
 EXPORT_SYMBOL(giveup_all);
 
+#ifdef CONFIG_PPC_BOOK3S_64
+#ifdef CONFIG_PPC_FPU
+static int restore_fp(struct task_struct *tsk)
+{
+	if (tsk->thread.load_fp) {
+		load_fp_state(&current->thread.fp_state);
+		current->thread.load_fp++;
+		return 1;
+	}
+	return 0;
+}
+#else
+static int restore_fp(struct task_struct *tsk) { return 0; }
+#endif /* CONFIG_PPC_FPU */
+
+#ifdef CONFIG_ALTIVEC
+#define loadvec(thr) ((thr).load_vec)
+static int restore_altivec(struct task_struct *tsk)
+{
+	if (cpu_has_feature(CPU_FTR_ALTIVEC) && (tsk->thread.load_vec)) {
+		load_vr_state(&tsk->thread.vr_state);
+		tsk->thread.used_vr = 1;
+		tsk->thread.load_vec++;
+
+		return 1;
+	}
+	return 0;
+}
+#else
+#define loadvec(thr) 0
+static inline int restore_altivec(struct task_struct *tsk) { return 0; }
+#endif /* CONFIG_ALTIVEC */
+
+#ifdef CONFIG_VSX
+static int restore_vsx(struct task_struct *tsk)
+{
+	if (cpu_has_feature(CPU_FTR_VSX)) {
+		tsk->thread.used_vsr = 1;
+		return 1;
+	}
+
+	return 0;
+}
+#else
+static inline int restore_vsx(struct task_struct *tsk) { return 0; }
+#endif /* CONFIG_VSX */
+
 /*
  * The exception exit path calls restore_math() with interrupts hard disabled
  * but the soft irq state not "reconciled". ftrace code that calls
@@ -551,6 +557,7 @@ void notrace restore_math(struct pt_regs *regs)
 
 	regs->msr = msr;
 }
+#endif
 
 static void save_all(struct task_struct *tsk)
 {

arch/powerpc/kernel/syscall_64.c

@@ -24,7 +24,11 @@ notrace long system_call_exception(long r3, long r4, long r5, long r6, long r7,
 	unsigned long ti_flags;
 	syscall_fn f;
 
+	if (IS_ENABLED(CONFIG_PPC_BOOK3S))
+		BUG_ON(!(regs->msr & MSR_RI));
 	BUG_ON(!(regs->msr & MSR_PR));
+	BUG_ON(!FULL_REGS(regs));
+	BUG_ON(regs->softe != IRQS_ENABLED);
 
 	account_cpu_user_entry();
 
@@ -196,7 +200,7 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3,
 		trace_hardirqs_off();
 		local_paca->irq_happened |= PACA_IRQ_HARD_DIS;
 		local_irq_enable();
-		/* Took an interrupt which may have more exit work to do. */
+		/* Took an interrupt, may have more exit work to do. */
 		goto again;
 	}
 	local_paca->irq_happened = 0;
@@ -212,3 +216,168 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3,
 
 	return ret;
 }
+
+#ifdef CONFIG_PPC_BOOK3S /* BOOK3E not yet using this */
+notrace unsigned long interrupt_exit_user_prepare(struct pt_regs *regs, unsigned long msr)
+{
+#ifdef CONFIG_PPC_BOOK3E
+	struct thread_struct *ts = &current->thread;
+#endif
+	unsigned long *ti_flagsp = &current_thread_info()->flags;
+	unsigned long ti_flags;
+	unsigned long flags;
+	unsigned long ret = 0;
+
+	if (IS_ENABLED(CONFIG_PPC_BOOK3S))
+		BUG_ON(!(regs->msr & MSR_RI));
+	BUG_ON(!(regs->msr & MSR_PR));
+	BUG_ON(!FULL_REGS(regs));
+	BUG_ON(regs->softe != IRQS_ENABLED);
+
+	local_irq_save(flags);
+
+again:
+	ti_flags = READ_ONCE(*ti_flagsp);
+	while (unlikely(ti_flags & (_TIF_USER_WORK_MASK & ~_TIF_RESTORE_TM))) {
+		local_irq_enable(); /* returning to user: may enable */
+		if (ti_flags & _TIF_NEED_RESCHED) {
+			schedule();
+		} else {
+			if (ti_flags & _TIF_SIGPENDING)
+				ret |= _TIF_RESTOREALL;
+			do_notify_resume(regs, ti_flags);
+		}
+		local_irq_disable();
+		ti_flags = READ_ONCE(*ti_flagsp);
+	}
+
+	if (IS_ENABLED(CONFIG_PPC_BOOK3S) && IS_ENABLED(CONFIG_PPC_FPU)) {
+		if (IS_ENABLED(CONFIG_PPC_TRANSACTIONAL_MEM) &&
+				unlikely((ti_flags & _TIF_RESTORE_TM))) {
+			restore_tm_state(regs);
+		} else {
+			unsigned long mathflags = MSR_FP;
+
+			if (cpu_has_feature(CPU_FTR_VSX))
+				mathflags |= MSR_VEC | MSR_VSX;
+			else if (cpu_has_feature(CPU_FTR_ALTIVEC))
+				mathflags |= MSR_VEC;
+
+			if ((regs->msr & mathflags) != mathflags)
+				restore_math(regs);
+		}
+	}
+
+	trace_hardirqs_on();
+	__hard_EE_RI_disable();
+	if (unlikely(lazy_irq_pending())) {
+		__hard_RI_enable();
+		trace_hardirqs_off();
+		local_paca->irq_happened |= PACA_IRQ_HARD_DIS;
+		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)) {
+		/*
+		 * Check to see if the dbcr0 register is set up to debug.
+		 * Use the internal debug mode bit to do this.
+		 */
+		mtmsr(mfmsr() & ~MSR_DE);
+		mtspr(SPRN_DBCR0, ts->debug.dbcr0);
+		mtspr(SPRN_DBSR, -1);
+	}
+#endif
+
+#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
+	local_paca->tm_scratch = regs->msr;
+#endif
+
+	kuap_check_amr();
+
+	account_cpu_user_exit();
+
+	return ret;
+}
+
+void unrecoverable_exception(struct pt_regs *regs);
+void preempt_schedule_irq(void);
+
+notrace unsigned long interrupt_exit_kernel_prepare(struct pt_regs *regs, unsigned long msr)
+{
+	unsigned long *ti_flagsp = &current_thread_info()->flags;
+	unsigned long flags;
+	unsigned long ret = 0;
+
+	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));
+
+	if (unlikely(*ti_flagsp & _TIF_EMULATE_STACK_STORE)) {
+		clear_bits(_TIF_EMULATE_STACK_STORE, ti_flagsp);
+		ret = 1;
+	}
+
+	local_irq_save(flags);
+
+	if (regs->softe == IRQS_ENABLED) {
+		/* Returning to a kernel context with local irqs enabled. */
+		WARN_ON_ONCE(!(regs->msr & MSR_EE));
+again:
+		if (IS_ENABLED(CONFIG_PREEMPT)) {
+			/* Return to preemptible kernel context */
+			if (unlikely(*ti_flagsp & _TIF_NEED_RESCHED)) {
+				if (preempt_count() == 0)
+					preempt_schedule_irq();
+			}
+		}
+
+		trace_hardirqs_on();
+		__hard_EE_RI_disable();
+		if (unlikely(lazy_irq_pending())) {
+			__hard_RI_enable();
+			irq_soft_mask_set(IRQS_ALL_DISABLED);
+			trace_hardirqs_off();
+			local_paca->irq_happened |= PACA_IRQ_HARD_DIS;
+			/*
+			 * Can't local_irq_restore to replay if we were in
+			 * interrupt context. Must replay directly.
+			 */
+			if (irqs_disabled_flags(flags)) {
+				replay_soft_interrupts();
+			} else {
+				local_irq_restore(flags);
+				local_irq_save(flags);
+			}
+			/* 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();
+		if (regs->msr & MSR_EE)
+			local_paca->irq_happened &= ~PACA_IRQ_HARD_DIS;
+	}
+
+
+#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
+	local_paca->tm_scratch = regs->msr;
+#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.
+	 */
+	kuap_restore_amr(regs);
+
+	return ret;
+}
+#endif

arch/powerpc/kernel/vector.S

@@ -134,7 +134,7 @@ _GLOBAL(load_up_vsx)
 	/* enable use of VSX after return */
 	oris	r12,r12,MSR_VSX@h
 	std	r12,_MSR(r1)
-	b	fast_exception_return
+	b	fast_interrupt_return
 
 #endif /* CONFIG_VSX */