[PATCH v6 0/2] powerpc/32: Implement C syscall entry/exit (complement)

[PATCH v6 0/2] powerpc/32: Implement C syscall entry/exit (complement)

[Christophe Leroy]

This series implements C syscall entry/exit for PPC32. It reuses
the work already done for PPC64.

This series is based on today's next-test (f538b53fd47a) where main patchs from v5 are merged in.

The first patch is important for performance.

v6:
- Forced scv param to 0 on syscall_exit_prepare(), and added is_not_scv bool.
- Reworked the last patch to avoid code duplication.

Christophe Leroy (2):
  powerpc/syscall: Do not check unsupported scv vector on PPC32
  powerpc/32: Handle bookE debugging in C in syscall entry/exit

 arch/powerpc/include/asm/interrupt.h | 12 +++++++
 arch/powerpc/include/asm/ptrace.h    |  5 +++
 arch/powerpc/include/asm/reg_booke.h |  3 ++
 arch/powerpc/kernel/entry_32.S       |  7 ----
 arch/powerpc/kernel/head_32.h        | 15 ---------
 arch/powerpc/kernel/head_booke.h     | 19 -----------
 arch/powerpc/kernel/interrupt.c      | 50 ++++++++++++++++++----------
 7 files changed, 52 insertions(+), 59 deletions(-)

-- 
2.25.0

[PATCH v6 0/2] powerpc/32: Implement C syscall entry/exit (complement)

[Christophe Leroy]

This series implements C syscall entry/exit for PPC32. It reuses
the work already done for PPC64.

This series is based on today's next-test (f538b53fd47a) where main patchs from v5 are merged in.

The first patch is important for performance.

v6:
- Forced scv param to 0 on syscall_exit_prepare(), and added is_not_scv bool.
- Reworked the last patch to avoid code duplication.

Christophe Leroy (2):
  powerpc/syscall: Do not check unsupported scv vector on PPC32
  powerpc/32: Handle bookE debugging in C in syscall entry/exit

 arch/powerpc/include/asm/interrupt.h | 12 +++++++
 arch/powerpc/include/asm/ptrace.h    |  5 +++
 arch/powerpc/include/asm/reg_booke.h |  3 ++
 arch/powerpc/kernel/entry_32.S       |  7 ----
 arch/powerpc/kernel/head_32.h        | 15 ---------
 arch/powerpc/kernel/head_booke.h     | 19 -----------
 arch/powerpc/kernel/interrupt.c      | 50 ++++++++++++++++++----------
 7 files changed, 52 insertions(+), 59 deletions(-)

-- 
2.25.0

[PATCH v6 1/2] powerpc/syscall: Do not check unsupported scv vector on PPC32

[Christophe Leroy]

Only book3s/64 has scv. No need to check the 0x7ff0 trap on 32 or 64e.
For that, add a helper trap_is_unsupported_scv() similar to
trap_is_scv().

And ignore the scv parameter in syscall_exit_prepare (Save 14 cycles
346 => 332 cycles)

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
v5: Added a helper trap_is_unsupported_scv()
v6: Still set r5 when calling syscall_exit_prepare() and introduce a local bool 'is_not_scv'
---
 arch/powerpc/include/asm/ptrace.h | 5 +++++
 arch/powerpc/kernel/interrupt.c   | 9 +++++----
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/include/asm/ptrace.h b/arch/powerpc/include/asm/ptrace.h
index 8236c5e749e4..975ba260006a 100644
--- a/arch/powerpc/include/asm/ptrace.h
+++ b/arch/powerpc/include/asm/ptrace.h
@@ -232,6 +232,11 @@ static inline bool trap_is_scv(struct pt_regs *regs)
 	return (IS_ENABLED(CONFIG_PPC_BOOK3S_64) && TRAP(regs) == 0x3000);
 }
 
+static inline bool trap_is_unsupported_scv(struct pt_regs *regs)
+{
+	return IS_ENABLED(CONFIG_PPC_BOOK3S_64) && TRAP(regs) == 0x7ff0;
+}
+
 static inline bool trap_is_syscall(struct pt_regs *regs)
 {
 	return (trap_is_scv(regs) || TRAP(regs) == 0xc00);
diff --git a/arch/powerpc/kernel/interrupt.c b/arch/powerpc/kernel/interrupt.c
index 107ec39f05cb..75d657b63332 100644
--- a/arch/powerpc/kernel/interrupt.c
+++ b/arch/powerpc/kernel/interrupt.c
@@ -88,7 +88,7 @@ notrace long system_call_exception(long r3, long r4, long r5,
 	local_irq_enable();
 
 	if (unlikely(current_thread_info()->flags & _TIF_SYSCALL_DOTRACE)) {
-		if (unlikely(regs->trap == 0x7ff0)) {
+		if (unlikely(trap_is_unsupported_scv(regs))) {
 			/* Unsupported scv vector */
 			_exception(SIGILL, regs, ILL_ILLOPC, regs->nip);
 			return regs->gpr[3];
@@ -111,7 +111,7 @@ notrace long system_call_exception(long r3, long r4, long r5,
 		r8 = regs->gpr[8];
 
 	} else if (unlikely(r0 >= NR_syscalls)) {
-		if (unlikely(regs->trap == 0x7ff0)) {
+		if (unlikely(trap_is_unsupported_scv(regs))) {
 			/* Unsupported scv vector */
 			_exception(SIGILL, regs, ILL_ILLOPC, regs->nip);
 			return regs->gpr[3];
@@ -220,6 +220,7 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3,
 	unsigned long *ti_flagsp = &current_thread_info()->flags;
 	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);
 
@@ -234,7 +235,7 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3,
 
 	ti_flags = *ti_flagsp;
 
-	if (unlikely(r3 >= (unsigned long)-MAX_ERRNO) && !scv) {
+	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 */
@@ -305,7 +306,7 @@ 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(!scv))) {
+	if (unlikely(!__prep_irq_for_enabled_exit(is_not_scv))) {
 		user_exit_irqoff();
 		local_irq_enable();
 		local_irq_disable();
-- 
2.25.0

[PATCH v6 1/2] powerpc/syscall: Do not check unsupported scv vector on PPC32

[Christophe Leroy]

Only book3s/64 has scv. No need to check the 0x7ff0 trap on 32 or 64e.
For that, add a helper trap_is_unsupported_scv() similar to
trap_is_scv().

And ignore the scv parameter in syscall_exit_prepare (Save 14 cycles
346 => 332 cycles)

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
v5: Added a helper trap_is_unsupported_scv()
v6: Still set r5 when calling syscall_exit_prepare() and introduce a local bool 'is_not_scv'
---
 arch/powerpc/include/asm/ptrace.h | 5 +++++
 arch/powerpc/kernel/interrupt.c   | 9 +++++----
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/include/asm/ptrace.h b/arch/powerpc/include/asm/ptrace.h
index 8236c5e749e4..975ba260006a 100644
--- a/arch/powerpc/include/asm/ptrace.h
+++ b/arch/powerpc/include/asm/ptrace.h
@@ -232,6 +232,11 @@ static inline bool trap_is_scv(struct pt_regs *regs)
 	return (IS_ENABLED(CONFIG_PPC_BOOK3S_64) && TRAP(regs) == 0x3000);
 }
 
+static inline bool trap_is_unsupported_scv(struct pt_regs *regs)
+{
+	return IS_ENABLED(CONFIG_PPC_BOOK3S_64) && TRAP(regs) == 0x7ff0;
+}
+
 static inline bool trap_is_syscall(struct pt_regs *regs)
 {
 	return (trap_is_scv(regs) || TRAP(regs) == 0xc00);
diff --git a/arch/powerpc/kernel/interrupt.c b/arch/powerpc/kernel/interrupt.c
index 107ec39f05cb..75d657b63332 100644
--- a/arch/powerpc/kernel/interrupt.c
+++ b/arch/powerpc/kernel/interrupt.c
@@ -88,7 +88,7 @@ notrace long system_call_exception(long r3, long r4, long r5,
 	local_irq_enable();
 
 	if (unlikely(current_thread_info()->flags & _TIF_SYSCALL_DOTRACE)) {
-		if (unlikely(regs->trap == 0x7ff0)) {
+		if (unlikely(trap_is_unsupported_scv(regs))) {
 			/* Unsupported scv vector */
 			_exception(SIGILL, regs, ILL_ILLOPC, regs->nip);
 			return regs->gpr[3];
@@ -111,7 +111,7 @@ notrace long system_call_exception(long r3, long r4, long r5,
 		r8 = regs->gpr[8];
 
 	} else if (unlikely(r0 >= NR_syscalls)) {
-		if (unlikely(regs->trap == 0x7ff0)) {
+		if (unlikely(trap_is_unsupported_scv(regs))) {
 			/* Unsupported scv vector */
 			_exception(SIGILL, regs, ILL_ILLOPC, regs->nip);
 			return regs->gpr[3];
@@ -220,6 +220,7 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3,
 	unsigned long *ti_flagsp = &current_thread_info()->flags;
 	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);
 
@@ -234,7 +235,7 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3,
 
 	ti_flags = *ti_flagsp;
 
-	if (unlikely(r3 >= (unsigned long)-MAX_ERRNO) && !scv) {
+	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 */
@@ -305,7 +306,7 @@ 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(!scv))) {
+	if (unlikely(!__prep_irq_for_enabled_exit(is_not_scv))) {
 		user_exit_irqoff();
 		local_irq_enable();
 		local_irq_disable();
-- 
2.25.0

[PATCH v6 2/2] powerpc/32: Handle bookE debugging in C in syscall entry/exit

[Christophe Leroy]

The handling of SPRN_DBCR0 and other registers can easily
be done in C instead of ASM.

For that, create booke_load_dbcr0() and booke_restore_dbcr0().

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
v5: New
v6: Refactor into helpers
---
 arch/powerpc/include/asm/interrupt.h | 12 ++++++++
 arch/powerpc/include/asm/reg_booke.h |  3 ++
 arch/powerpc/kernel/entry_32.S       |  7 -----
 arch/powerpc/kernel/head_32.h        | 15 ----------
 arch/powerpc/kernel/head_booke.h     | 19 -------------
 arch/powerpc/kernel/interrupt.c      | 41 ++++++++++++++++++----------
 6 files changed, 42 insertions(+), 55 deletions(-)

diff --git a/arch/powerpc/include/asm/interrupt.h b/arch/powerpc/include/asm/interrupt.h
index 4badb3e51c19..e62c37915bbe 100644
--- a/arch/powerpc/include/asm/interrupt.h
+++ b/arch/powerpc/include/asm/interrupt.h
@@ -14,6 +14,18 @@ struct interrupt_state {
 #endif
 };
 
+static inline void booke_restore_dbcr0(void)
+{
+#ifdef CONFIG_PPC_ADV_DEBUG_REGS
+	unsigned long dbcr0 = current->thread.debug.dbcr0;
+
+	if (IS_ENABLED(CONFIG_PPC32) && unlikely(dbcr0 & DBCR0_IDM)) {
+		mtspr(SPRN_DBSR, -1);
+		mtspr(SPRN_DBCR0, global_dbcr0[smp_processor_id()]);
+	}
+#endif
+}
+
 static inline void interrupt_enter_prepare(struct pt_regs *regs, struct interrupt_state *state)
 {
 	/*
diff --git a/arch/powerpc/include/asm/reg_booke.h b/arch/powerpc/include/asm/reg_booke.h
index 262782f08fd4..17b8dcd9a40d 100644
--- a/arch/powerpc/include/asm/reg_booke.h
+++ b/arch/powerpc/include/asm/reg_booke.h
@@ -691,6 +691,9 @@
 #define mttmr(rn, v)	asm volatile(MTTMR(rn, %0) : \
 				     : "r" ((unsigned long)(v)) \
 				     : "memory")
+
+extern unsigned long global_dbcr0[];
+
 #endif /* !__ASSEMBLY__ */
 
 #endif /* __ASM_POWERPC_REG_BOOKE_H__ */
diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index 9dd90be9f8a5..78c430b7f9d9 100644
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -343,13 +343,6 @@ ret_from_syscall:
 	addi    r4,r1,STACK_FRAME_OVERHEAD
 	li	r5,0
 	bl	syscall_exit_prepare
-#if defined(CONFIG_4xx) || defined(CONFIG_BOOKE)
-	/* If the process has its own DBCR0 value, load it up.  The internal
-	   debug mode bit tells us that dbcr0 should be loaded. */
-	lwz	r0,THREAD+THREAD_DBCR0(r2)
-	andis.	r10,r0,DBCR0_IDM@h
-	bnel-	load_dbcr0
-#endif
 #ifdef CONFIG_PPC_47x
 	lis	r4,icache_44x_need_flush@ha
 	lwz	r5,icache_44x_need_flush@l(r4)
diff --git a/arch/powerpc/kernel/head_32.h b/arch/powerpc/kernel/head_32.h
index 1afad7bc3395..5d4706c14572 100644
--- a/arch/powerpc/kernel/head_32.h
+++ b/arch/powerpc/kernel/head_32.h
@@ -153,21 +153,6 @@
 	SAVE_4GPRS(3, r11)
 	SAVE_2GPRS(7, r11)
 	addi	r2,r12,-THREAD
-#if defined(CONFIG_40x)
-	/* Check to see if the dbcr0 register is set up to debug.  Use the
-	   internal debug mode bit to do this. */
-	lwz	r12,THREAD_DBCR0(r12)
-	andis.	r12,r12,DBCR0_IDM@h
-	beq+	3f
-	/* From user and task is ptraced - load up global dbcr0 */
-	li	r12,-1			/* clear all pending debug events */
-	mtspr	SPRN_DBSR,r12
-	lis	r11,global_dbcr0@ha
-	addi	r11,r11,global_dbcr0@l
-	lwz	r12,0(r11)
-	mtspr	SPRN_DBCR0,r12
-3:
-#endif
 	b	transfer_to_syscall		/* jump to handler */
 .endm
 
diff --git a/arch/powerpc/kernel/head_booke.h b/arch/powerpc/kernel/head_booke.h
index 5f565232b99d..47857795f50a 100644
--- a/arch/powerpc/kernel/head_booke.h
+++ b/arch/powerpc/kernel/head_booke.h
@@ -130,25 +130,6 @@ ALT_FTR_SECTION_END_IFSET(CPU_FTR_EMB_HV)
 	SAVE_2GPRS(7, r11)
 
 	addi	r2,r10,-THREAD
-	/* Check to see if the dbcr0 register is set up to debug.  Use the
-	   internal debug mode bit to do this. */
-	lwz	r12,THREAD_DBCR0(r10)
-	andis.	r12,r12,DBCR0_IDM@h
-	beq+	3f
-	/* From user and task is ptraced - load up global dbcr0 */
-	li	r12,-1			/* clear all pending debug events */
-	mtspr	SPRN_DBSR,r12
-	lis	r11,global_dbcr0@ha
-	addi	r11,r11,global_dbcr0@l
-#ifdef CONFIG_SMP
-	lwz	r10, TASK_CPU(r2)
-	slwi	r10, r10, 2
-	add	r11, r11, r10
-#endif
-	lwz	r12,0(r11)
-	mtspr	SPRN_DBCR0,r12
-
-3:
 	b	transfer_to_syscall	/* jump to handler */
 .endm
 
diff --git a/arch/powerpc/kernel/interrupt.c b/arch/powerpc/kernel/interrupt.c
index 75d657b63332..f93664ad4a5e 100644
--- a/arch/powerpc/kernel/interrupt.c
+++ b/arch/powerpc/kernel/interrupt.c
@@ -73,6 +73,8 @@ notrace long system_call_exception(long r3, long r4, long r5,
 		kuap_check_amr();
 #endif
 
+	booke_restore_dbcr0();
+
 	account_cpu_user_entry();
 
 	account_stolen_time();
@@ -204,6 +206,28 @@ static notrace inline bool prep_irq_for_enabled_exit(bool clear_ri, bool irqs_en
 	return false;
 }
 
+static notrace void booke_load_dbcr0(void)
+{
+#ifdef CONFIG_PPC_ADV_DEBUG_REGS
+	unsigned long dbcr0 = current->thread.debug.dbcr0;
+
+	if (likely(!(dbcr0 & DBCR0_IDM)))
+		return;
+
+	/*
+	 * 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);
+	if (IS_ENABLED(CONFIG_PPC32)) {
+		isync();
+		global_dbcr0[smp_processor_id()] = mfspr(SPRN_DBCR0);
+	}
+	mtspr(SPRN_DBCR0, dbcr0);
+	mtspr(SPRN_DBSR, -1);
+#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
@@ -317,6 +341,8 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3,
 	local_paca->tm_scratch = regs->msr;
 #endif
 
+	booke_load_dbcr0();
+
 	account_cpu_user_exit();
 
 #ifdef CONFIG_PPC_BOOK3S_64 /* BOOK3E and ppc32 not using this */
@@ -331,9 +357,6 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3,
 #ifndef CONFIG_PPC_BOOK3E_64 /* 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;
@@ -398,17 +421,7 @@ notrace unsigned long interrupt_exit_user_prepare(struct pt_regs *regs, unsigned
 		goto again;
 	}
 
-#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
+	booke_load_dbcr0();
 
 #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
 	local_paca->tm_scratch = regs->msr;
-- 
2.25.0

[PATCH v6 2/2] powerpc/32: Handle bookE debugging in C in syscall entry/exit

[Christophe Leroy]

The handling of SPRN_DBCR0 and other registers can easily
be done in C instead of ASM.

For that, create booke_load_dbcr0() and booke_restore_dbcr0().

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
v5: New
v6: Refactor into helpers
---
 arch/powerpc/include/asm/interrupt.h | 12 ++++++++
 arch/powerpc/include/asm/reg_booke.h |  3 ++
 arch/powerpc/kernel/entry_32.S       |  7 -----
 arch/powerpc/kernel/head_32.h        | 15 ----------
 arch/powerpc/kernel/head_booke.h     | 19 -------------
 arch/powerpc/kernel/interrupt.c      | 41 ++++++++++++++++++----------
 6 files changed, 42 insertions(+), 55 deletions(-)

diff --git a/arch/powerpc/include/asm/interrupt.h b/arch/powerpc/include/asm/interrupt.h
index 4badb3e51c19..e62c37915bbe 100644
--- a/arch/powerpc/include/asm/interrupt.h
+++ b/arch/powerpc/include/asm/interrupt.h
@@ -14,6 +14,18 @@ struct interrupt_state {
 #endif
 };
 
+static inline void booke_restore_dbcr0(void)
+{
+#ifdef CONFIG_PPC_ADV_DEBUG_REGS
+	unsigned long dbcr0 = current->thread.debug.dbcr0;
+
+	if (IS_ENABLED(CONFIG_PPC32) && unlikely(dbcr0 & DBCR0_IDM)) {
+		mtspr(SPRN_DBSR, -1);
+		mtspr(SPRN_DBCR0, global_dbcr0[smp_processor_id()]);
+	}
+#endif
+}
+
 static inline void interrupt_enter_prepare(struct pt_regs *regs, struct interrupt_state *state)
 {
 	/*
diff --git a/arch/powerpc/include/asm/reg_booke.h b/arch/powerpc/include/asm/reg_booke.h
index 262782f08fd4..17b8dcd9a40d 100644
--- a/arch/powerpc/include/asm/reg_booke.h
+++ b/arch/powerpc/include/asm/reg_booke.h
@@ -691,6 +691,9 @@
 #define mttmr(rn, v)	asm volatile(MTTMR(rn, %0) : \
 				     : "r" ((unsigned long)(v)) \
 				     : "memory")
+
+extern unsigned long global_dbcr0[];
+
 #endif /* !__ASSEMBLY__ */
 
 #endif /* __ASM_POWERPC_REG_BOOKE_H__ */
diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index 9dd90be9f8a5..78c430b7f9d9 100644
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -343,13 +343,6 @@ ret_from_syscall:
 	addi    r4,r1,STACK_FRAME_OVERHEAD
 	li	r5,0
 	bl	syscall_exit_prepare
-#if defined(CONFIG_4xx) || defined(CONFIG_BOOKE)
-	/* If the process has its own DBCR0 value, load it up.  The internal
-	   debug mode bit tells us that dbcr0 should be loaded. */
-	lwz	r0,THREAD+THREAD_DBCR0(r2)
-	andis.	r10,r0,DBCR0_IDM@h
-	bnel-	load_dbcr0
-#endif
 #ifdef CONFIG_PPC_47x
 	lis	r4,icache_44x_need_flush@ha
 	lwz	r5,icache_44x_need_flush@l(r4)
diff --git a/arch/powerpc/kernel/head_32.h b/arch/powerpc/kernel/head_32.h
index 1afad7bc3395..5d4706c14572 100644
--- a/arch/powerpc/kernel/head_32.h
+++ b/arch/powerpc/kernel/head_32.h
@@ -153,21 +153,6 @@
 	SAVE_4GPRS(3, r11)
 	SAVE_2GPRS(7, r11)
 	addi	r2,r12,-THREAD
-#if defined(CONFIG_40x)
-	/* Check to see if the dbcr0 register is set up to debug.  Use the
-	   internal debug mode bit to do this. */
-	lwz	r12,THREAD_DBCR0(r12)
-	andis.	r12,r12,DBCR0_IDM@h
-	beq+	3f
-	/* From user and task is ptraced - load up global dbcr0 */
-	li	r12,-1			/* clear all pending debug events */
-	mtspr	SPRN_DBSR,r12
-	lis	r11,global_dbcr0@ha
-	addi	r11,r11,global_dbcr0@l
-	lwz	r12,0(r11)
-	mtspr	SPRN_DBCR0,r12
-3:
-#endif
 	b	transfer_to_syscall		/* jump to handler */
 .endm
 
diff --git a/arch/powerpc/kernel/head_booke.h b/arch/powerpc/kernel/head_booke.h
index 5f565232b99d..47857795f50a 100644
--- a/arch/powerpc/kernel/head_booke.h
+++ b/arch/powerpc/kernel/head_booke.h
@@ -130,25 +130,6 @@ ALT_FTR_SECTION_END_IFSET(CPU_FTR_EMB_HV)
 	SAVE_2GPRS(7, r11)
 
 	addi	r2,r10,-THREAD
-	/* Check to see if the dbcr0 register is set up to debug.  Use the
-	   internal debug mode bit to do this. */
-	lwz	r12,THREAD_DBCR0(r10)
-	andis.	r12,r12,DBCR0_IDM@h
-	beq+	3f
-	/* From user and task is ptraced - load up global dbcr0 */
-	li	r12,-1			/* clear all pending debug events */
-	mtspr	SPRN_DBSR,r12
-	lis	r11,global_dbcr0@ha
-	addi	r11,r11,global_dbcr0@l
-#ifdef CONFIG_SMP
-	lwz	r10, TASK_CPU(r2)
-	slwi	r10, r10, 2
-	add	r11, r11, r10
-#endif
-	lwz	r12,0(r11)
-	mtspr	SPRN_DBCR0,r12
-
-3:
 	b	transfer_to_syscall	/* jump to handler */
 .endm
 
diff --git a/arch/powerpc/kernel/interrupt.c b/arch/powerpc/kernel/interrupt.c
index 75d657b63332..f93664ad4a5e 100644
--- a/arch/powerpc/kernel/interrupt.c
+++ b/arch/powerpc/kernel/interrupt.c
@@ -73,6 +73,8 @@ notrace long system_call_exception(long r3, long r4, long r5,
 		kuap_check_amr();
 #endif
 
+	booke_restore_dbcr0();
+
 	account_cpu_user_entry();
 
 	account_stolen_time();
@@ -204,6 +206,28 @@ static notrace inline bool prep_irq_for_enabled_exit(bool clear_ri, bool irqs_en
 	return false;
 }
 
+static notrace void booke_load_dbcr0(void)
+{
+#ifdef CONFIG_PPC_ADV_DEBUG_REGS
+	unsigned long dbcr0 = current->thread.debug.dbcr0;
+
+	if (likely(!(dbcr0 & DBCR0_IDM)))
+		return;
+
+	/*
+	 * 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);
+	if (IS_ENABLED(CONFIG_PPC32)) {
+		isync();
+		global_dbcr0[smp_processor_id()] = mfspr(SPRN_DBCR0);
+	}
+	mtspr(SPRN_DBCR0, dbcr0);
+	mtspr(SPRN_DBSR, -1);
+#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
@@ -317,6 +341,8 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3,
 	local_paca->tm_scratch = regs->msr;
 #endif
 
+	booke_load_dbcr0();
+
 	account_cpu_user_exit();
 
 #ifdef CONFIG_PPC_BOOK3S_64 /* BOOK3E and ppc32 not using this */
@@ -331,9 +357,6 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3,
 #ifndef CONFIG_PPC_BOOK3E_64 /* 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;
@@ -398,17 +421,7 @@ notrace unsigned long interrupt_exit_user_prepare(struct pt_regs *regs, unsigned
 		goto again;
 	}
 
-#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
+	booke_load_dbcr0();
 
 #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
 	local_paca->tm_scratch = regs->msr;
-- 
2.25.0

[PATCH v6 3/2] powerpc/syscall: Avoid storing 'current' in another pointer

[Christophe Leroy]

By saving the pointer pointing to thread_info.flags, gcc copies r2
in a non-volatile register.

We know 'current' doesn't change, so avoid that intermediaite pointer.

Reduces null_syscall benchmark by 2 cycles (322 => 320 cycles)

On PPC64, gcc seems to know that 'current' is not changing, and it keeps
it in a non volatile register to avoid multiple read of 'current' in paca.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
v5: Also in interrupt exit prepare
v6: Removed change related to booke current->thread.debug
v7: Rebased on top of "powerpc/32: Handle bookE debugging in C in syscall entry/exit"
---
 arch/powerpc/kernel/interrupt.c | 21 +++++++++------------
 1 file changed, 9 insertions(+), 12 deletions(-)

diff --git a/arch/powerpc/kernel/interrupt.c b/arch/powerpc/kernel/interrupt.c
index f93664ad4a5e..398cd86b6ada 100644
--- a/arch/powerpc/kernel/interrupt.c
+++ b/arch/powerpc/kernel/interrupt.c
@@ -241,7 +241,6 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3,
 					   struct pt_regs *regs,
 					   long scv)
 {
-	unsigned long *ti_flagsp = &current_thread_info()->flags;
 	unsigned long ti_flags;
 	unsigned long ret = 0;
 	bool is_not_scv = !IS_ENABLED(CONFIG_PPC_BOOK3S_64) || !scv;
@@ -257,7 +256,7 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3,
 	/* Check whether the syscall is issued inside a restartable sequence */
 	rseq_syscall(regs);
 
-	ti_flags = *ti_flagsp;
+	ti_flags = current_thread_info()->flags;
 
 	if (unlikely(r3 >= (unsigned long)-MAX_ERRNO) && is_not_scv) {
 		if (likely(!(ti_flags & (_TIF_NOERROR | _TIF_RESTOREALL)))) {
@@ -271,7 +270,7 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3,
 			ret = _TIF_RESTOREALL;
 		else
 			regs->gpr[3] = r3;
-		clear_bits(_TIF_PERSYSCALL_MASK, ti_flagsp);
+		clear_bits(_TIF_PERSYSCALL_MASK, &current_thread_info()->flags);
 	} else {
 		regs->gpr[3] = r3;
 	}
@@ -284,7 +283,7 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3,
 	local_irq_disable();
 
 again:
-	ti_flags = READ_ONCE(*ti_flagsp);
+	ti_flags = READ_ONCE(current_thread_info()->flags);
 	while (unlikely(ti_flags & (_TIF_USER_WORK_MASK & ~_TIF_RESTORE_TM))) {
 		local_irq_enable();
 		if (ti_flags & _TIF_NEED_RESCHED) {
@@ -300,7 +299,7 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3,
 			do_notify_resume(regs, ti_flags);
 		}
 		local_irq_disable();
-		ti_flags = READ_ONCE(*ti_flagsp);
+		ti_flags = READ_ONCE(current_thread_info()->flags);
 	}
 
 	if (IS_ENABLED(CONFIG_PPC_BOOK3S) && IS_ENABLED(CONFIG_PPC_FPU)) {
@@ -357,7 +356,6 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3,
 #ifndef CONFIG_PPC_BOOK3E_64 /* BOOK3E not yet using this */
 notrace unsigned long interrupt_exit_user_prepare(struct pt_regs *regs, unsigned long msr)
 {
-	unsigned long *ti_flagsp = &current_thread_info()->flags;
 	unsigned long ti_flags;
 	unsigned long flags;
 	unsigned long ret = 0;
@@ -380,7 +378,7 @@ notrace unsigned long interrupt_exit_user_prepare(struct pt_regs *regs, unsigned
 	local_irq_save(flags);
 
 again:
-	ti_flags = READ_ONCE(*ti_flagsp);
+	ti_flags = READ_ONCE(current_thread_info()->flags);
 	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) {
@@ -391,7 +389,7 @@ notrace unsigned long interrupt_exit_user_prepare(struct pt_regs *regs, unsigned
 			do_notify_resume(regs, ti_flags);
 		}
 		local_irq_disable();
-		ti_flags = READ_ONCE(*ti_flagsp);
+		ti_flags = READ_ONCE(current_thread_info()->flags);
 	}
 
 	if (IS_ENABLED(CONFIG_PPC_BOOK3S) && IS_ENABLED(CONFIG_PPC_FPU)) {
@@ -443,7 +441,6 @@ 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;
 #ifdef CONFIG_PPC64
@@ -466,8 +463,8 @@ notrace unsigned long interrupt_exit_kernel_prepare(struct pt_regs *regs, unsign
 	amr = kuap_get_and_check_amr();
 #endif
 
-	if (unlikely(*ti_flagsp & _TIF_EMULATE_STACK_STORE)) {
-		clear_bits(_TIF_EMULATE_STACK_STORE, ti_flagsp);
+	if (unlikely(current_thread_info()->flags & _TIF_EMULATE_STACK_STORE)) {
+		clear_bits(_TIF_EMULATE_STACK_STORE, &current_thread_info()->flags);
 		ret = 1;
 	}
 
@@ -479,7 +476,7 @@ notrace unsigned long interrupt_exit_kernel_prepare(struct pt_regs *regs, unsign
 again:
 		if (IS_ENABLED(CONFIG_PREEMPT)) {
 			/* Return to preemptible kernel context */
-			if (unlikely(*ti_flagsp & _TIF_NEED_RESCHED)) {
+			if (unlikely(current_thread_info()->flags & _TIF_NEED_RESCHED)) {
 				if (preempt_count() == 0)
 					preempt_schedule_irq();
 			}
-- 
2.25.0

[PATCH v6 3/2] powerpc/syscall: Avoid storing 'current' in another pointer

[Christophe Leroy]

By saving the pointer pointing to thread_info.flags, gcc copies r2
in a non-volatile register.

We know 'current' doesn't change, so avoid that intermediaite pointer.

Reduces null_syscall benchmark by 2 cycles (322 => 320 cycles)

On PPC64, gcc seems to know that 'current' is not changing, and it keeps
it in a non volatile register to avoid multiple read of 'current' in paca.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
v5: Also in interrupt exit prepare
v6: Removed change related to booke current->thread.debug
v7: Rebased on top of "powerpc/32: Handle bookE debugging in C in syscall entry/exit"
---
 arch/powerpc/kernel/interrupt.c | 21 +++++++++------------
 1 file changed, 9 insertions(+), 12 deletions(-)

diff --git a/arch/powerpc/kernel/interrupt.c b/arch/powerpc/kernel/interrupt.c
index f93664ad4a5e..398cd86b6ada 100644
--- a/arch/powerpc/kernel/interrupt.c
+++ b/arch/powerpc/kernel/interrupt.c
@@ -241,7 +241,6 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3,
 					   struct pt_regs *regs,
 					   long scv)
 {
-	unsigned long *ti_flagsp = &current_thread_info()->flags;
 	unsigned long ti_flags;
 	unsigned long ret = 0;
 	bool is_not_scv = !IS_ENABLED(CONFIG_PPC_BOOK3S_64) || !scv;
@@ -257,7 +256,7 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3,
 	/* Check whether the syscall is issued inside a restartable sequence */
 	rseq_syscall(regs);
 
-	ti_flags = *ti_flagsp;
+	ti_flags = current_thread_info()->flags;
 
 	if (unlikely(r3 >= (unsigned long)-MAX_ERRNO) && is_not_scv) {
 		if (likely(!(ti_flags & (_TIF_NOERROR | _TIF_RESTOREALL)))) {
@@ -271,7 +270,7 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3,
 			ret = _TIF_RESTOREALL;
 		else
 			regs->gpr[3] = r3;
-		clear_bits(_TIF_PERSYSCALL_MASK, ti_flagsp);
+		clear_bits(_TIF_PERSYSCALL_MASK, &current_thread_info()->flags);
 	} else {
 		regs->gpr[3] = r3;
 	}
@@ -284,7 +283,7 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3,
 	local_irq_disable();
 
 again:
-	ti_flags = READ_ONCE(*ti_flagsp);
+	ti_flags = READ_ONCE(current_thread_info()->flags);
 	while (unlikely(ti_flags & (_TIF_USER_WORK_MASK & ~_TIF_RESTORE_TM))) {
 		local_irq_enable();
 		if (ti_flags & _TIF_NEED_RESCHED) {
@@ -300,7 +299,7 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3,
 			do_notify_resume(regs, ti_flags);
 		}
 		local_irq_disable();
-		ti_flags = READ_ONCE(*ti_flagsp);
+		ti_flags = READ_ONCE(current_thread_info()->flags);
 	}
 
 	if (IS_ENABLED(CONFIG_PPC_BOOK3S) && IS_ENABLED(CONFIG_PPC_FPU)) {
@@ -357,7 +356,6 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3,
 #ifndef CONFIG_PPC_BOOK3E_64 /* BOOK3E not yet using this */
 notrace unsigned long interrupt_exit_user_prepare(struct pt_regs *regs, unsigned long msr)
 {
-	unsigned long *ti_flagsp = &current_thread_info()->flags;
 	unsigned long ti_flags;
 	unsigned long flags;
 	unsigned long ret = 0;
@@ -380,7 +378,7 @@ notrace unsigned long interrupt_exit_user_prepare(struct pt_regs *regs, unsigned
 	local_irq_save(flags);
 
 again:
-	ti_flags = READ_ONCE(*ti_flagsp);
+	ti_flags = READ_ONCE(current_thread_info()->flags);
 	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) {
@@ -391,7 +389,7 @@ notrace unsigned long interrupt_exit_user_prepare(struct pt_regs *regs, unsigned
 			do_notify_resume(regs, ti_flags);
 		}
 		local_irq_disable();
-		ti_flags = READ_ONCE(*ti_flagsp);
+		ti_flags = READ_ONCE(current_thread_info()->flags);
 	}
 
 	if (IS_ENABLED(CONFIG_PPC_BOOK3S) && IS_ENABLED(CONFIG_PPC_FPU)) {
@@ -443,7 +441,6 @@ 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;
 #ifdef CONFIG_PPC64
@@ -466,8 +463,8 @@ notrace unsigned long interrupt_exit_kernel_prepare(struct pt_regs *regs, unsign
 	amr = kuap_get_and_check_amr();
 #endif
 
-	if (unlikely(*ti_flagsp & _TIF_EMULATE_STACK_STORE)) {
-		clear_bits(_TIF_EMULATE_STACK_STORE, ti_flagsp);
+	if (unlikely(current_thread_info()->flags & _TIF_EMULATE_STACK_STORE)) {
+		clear_bits(_TIF_EMULATE_STACK_STORE, &current_thread_info()->flags);
 		ret = 1;
 	}
 
@@ -479,7 +476,7 @@ notrace unsigned long interrupt_exit_kernel_prepare(struct pt_regs *regs, unsign
 again:
 		if (IS_ENABLED(CONFIG_PREEMPT)) {
 			/* Return to preemptible kernel context */
-			if (unlikely(*ti_flagsp & _TIF_NEED_RESCHED)) {
+			if (unlikely(current_thread_info()->flags & _TIF_NEED_RESCHED)) {
 				if (preempt_count() == 0)
 					preempt_schedule_irq();
 			}
-- 
2.25.0

Re: [PATCH v6 0/2] powerpc/32: Implement C syscall entry/exit (complement)

[Michael Ellerman]

On Tue, 9 Feb 2021 19:29:26 +0000 (UTC), Christophe Leroy wrote:
> This series implements C syscall entry/exit for PPC32. It reuses
> the work already done for PPC64.
> 
> This series is based on today's next-test (f538b53fd47a) where main patchs from v5 are merged in.
> 
> The first patch is important for performance.
> 
> [...]

Applied to powerpc/next.

[1/3] powerpc/syscall: Do not check unsupported scv vector on PPC32
      https://git.kernel.org/powerpc/c/b966f2279048ee9f30d83ef8568b99fa40917c54
[2/3] powerpc/32: Handle bookE debugging in C in syscall entry/exit
      https://git.kernel.org/powerpc/c/d524dda719f06967db4d3ba519edf9267f84c155
[3/3] powerpc/syscall: Avoid storing 'current' in another pointer
      https://git.kernel.org/powerpc/c/5b90b9661a3396e00f6e8bcbb617a0787fb683d0

cheers

Re: [PATCH v6 0/2] powerpc/32: Implement C syscall entry/exit (complement)

[Michael Ellerman]

On Tue, 9 Feb 2021 19:29:26 +0000 (UTC), Christophe Leroy wrote:
> This series implements C syscall entry/exit for PPC32. It reuses
> the work already done for PPC64.
> 
> This series is based on today's next-test (f538b53fd47a) where main patchs from v5 are merged in.
> 
> The first patch is important for performance.
> 
> [...]

Applied to powerpc/next.

[1/3] powerpc/syscall: Do not check unsupported scv vector on PPC32
      https://git.kernel.org/powerpc/c/b966f2279048ee9f30d83ef8568b99fa40917c54
[2/3] powerpc/32: Handle bookE debugging in C in syscall entry/exit
      https://git.kernel.org/powerpc/c/d524dda719f06967db4d3ba519edf9267f84c155
[3/3] powerpc/syscall: Avoid storing 'current' in another pointer
      https://git.kernel.org/powerpc/c/5b90b9661a3396e00f6e8bcbb617a0787fb683d0

cheers