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* [PATCH v4 1/2] powerpc/irq: bring back ksp_limit management in C functions.
@ 2019-10-10  5:36 Christophe Leroy
  2019-10-10  5:36 ` [PATCH v4 2/2] powerpc/irq: inline call_do_irq() and call_do_softirq() Christophe Leroy
  0 siblings, 1 reply; 2+ messages in thread
From: Christophe Leroy @ 2019-10-10  5:36 UTC (permalink / raw)
  To: Benjamin Herrenschmidt, Paul Mackerras, Michael Ellerman, segher
  Cc: linuxppc-dev, linux-kernel

Commit cbc9565ee826 ("powerpc: Remove ksp_limit on ppc64") moved
PPC32 ksp_limit handling in assembly functions call_do_softirq()
and call_do_irq() as they are different for PPC32 and PPC64.

In preparation of replacing these functions by inline assembly,
partialy revert that commit to bring back ksp_limit assignment
in the callers.

To get and set ksp_limit without a forest of #ifdefs CONFIG_PPC32,
use helpers that will void on PPC64.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>

---
v2: added forward declaration of struct task_struct to avoid build failure.
v3: included linux/sched.h, forward declaration is not enough.
v4: no change
---
 arch/powerpc/include/asm/irq.h | 22 ++++++++++++++++++++++
 arch/powerpc/kernel/irq.c      | 14 +++++++++++++-
 arch/powerpc/kernel/misc_32.S  | 14 --------------
 3 files changed, 35 insertions(+), 15 deletions(-)

diff --git a/arch/powerpc/include/asm/irq.h b/arch/powerpc/include/asm/irq.h
index 814dfab7e392..0c6469983c66 100644
--- a/arch/powerpc/include/asm/irq.h
+++ b/arch/powerpc/include/asm/irq.h
@@ -10,6 +10,7 @@
 #include <linux/threads.h>
 #include <linux/list.h>
 #include <linux/radix-tree.h>
+#include <linux/sched.h>
 
 #include <asm/types.h>
 #include <linux/atomic.h>
@@ -64,5 +65,26 @@ extern void __do_irq(struct pt_regs *regs);
 
 int irq_choose_cpu(const struct cpumask *mask);
 
+#ifdef CONFIG_PPC32
+static inline unsigned long get_ksp_limit(struct task_struct *tsk)
+{
+	return tsk->thread.ksp_limit;
+}
+
+static inline void set_ksp_limit(struct task_struct *tsk, unsigned long limit)
+{
+	tsk->thread.ksp_limit = limit;
+}
+#else
+static inline unsigned long get_ksp_limit(struct task_struct *tsk)
+{
+	return 0;
+}
+
+static inline void set_ksp_limit(struct task_struct *tsk, unsigned long limit)
+{
+}
+#endif
+
 #endif /* _ASM_IRQ_H */
 #endif /* __KERNEL__ */
diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
index 5645bc9cbc09..04204be49577 100644
--- a/arch/powerpc/kernel/irq.c
+++ b/arch/powerpc/kernel/irq.c
@@ -646,6 +646,7 @@ void do_IRQ(struct pt_regs *regs)
 {
 	struct pt_regs *old_regs = set_irq_regs(regs);
 	void *cursp, *irqsp, *sirqsp;
+	unsigned long saved_ksp_limit = get_ksp_limit(current);
 
 	/* Switch to the irq stack to handle this */
 	cursp = (void *)(current_stack_pointer() & ~(THREAD_SIZE - 1));
@@ -658,9 +659,15 @@ void do_IRQ(struct pt_regs *regs)
 		set_irq_regs(old_regs);
 		return;
 	}
+	/* Adjust the stack limit */
+	set_ksp_limit(current, (unsigned long)irqsp);
+
 	/* Switch stack and call */
 	call_do_irq(regs, irqsp);
 
+	/* Restore stack limit */
+	set_ksp_limit(current, saved_ksp_limit);
+
 	set_irq_regs(old_regs);
 }
 
@@ -681,7 +688,12 @@ void *hardirq_ctx[NR_CPUS] __read_mostly;
 
 void do_softirq_own_stack(void)
 {
-	call_do_softirq(softirq_ctx[smp_processor_id()]);
+	void *irqsp = softirq_ctx[smp_processor_id()];
+	unsigned long saved_ksp_limit = get_ksp_limit(current);
+
+	set_ksp_limit(current, (unsigned long)irqsp);
+	call_do_softirq(irqsp);
+	set_ksp_limit(current, saved_ksp_limit);
 }
 
 irq_hw_number_t virq_to_hw(unsigned int virq)
diff --git a/arch/powerpc/kernel/misc_32.S b/arch/powerpc/kernel/misc_32.S
index 82df4b09e79f..a5422f7782b3 100644
--- a/arch/powerpc/kernel/misc_32.S
+++ b/arch/powerpc/kernel/misc_32.S
@@ -33,23 +33,14 @@
 
 	.text
 
-/*
- * We store the saved ksp_limit in the unused part
- * of the STACK_FRAME_OVERHEAD
- */
 _GLOBAL(call_do_softirq)
 	mflr	r0
 	stw	r0,4(r1)
-	lwz	r10,THREAD+KSP_LIMIT(r2)
-	stw	r3, THREAD+KSP_LIMIT(r2)
 	stwu	r1,THREAD_SIZE-STACK_FRAME_OVERHEAD(r3)
 	mr	r1,r3
-	stw	r10,8(r1)
 	bl	__do_softirq
-	lwz	r10,8(r1)
 	lwz	r1,0(r1)
 	lwz	r0,4(r1)
-	stw	r10,THREAD+KSP_LIMIT(r2)
 	mtlr	r0
 	blr
 
@@ -59,16 +50,11 @@ _GLOBAL(call_do_softirq)
 _GLOBAL(call_do_irq)
 	mflr	r0
 	stw	r0,4(r1)
-	lwz	r10,THREAD+KSP_LIMIT(r2)
-	stw	r4, THREAD+KSP_LIMIT(r2)
 	stwu	r1,THREAD_SIZE-STACK_FRAME_OVERHEAD(r4)
 	mr	r1,r4
-	stw	r10,8(r1)
 	bl	__do_irq
-	lwz	r10,8(r1)
 	lwz	r1,0(r1)
 	lwz	r0,4(r1)
-	stw	r10,THREAD+KSP_LIMIT(r2)
 	mtlr	r0
 	blr
 
-- 
2.13.3


^ permalink raw reply	[flat|nested] 2+ messages in thread

* [PATCH v4 2/2] powerpc/irq: inline call_do_irq() and call_do_softirq()
  2019-10-10  5:36 [PATCH v4 1/2] powerpc/irq: bring back ksp_limit management in C functions Christophe Leroy
@ 2019-10-10  5:36 ` Christophe Leroy
  0 siblings, 0 replies; 2+ messages in thread
From: Christophe Leroy @ 2019-10-10  5:36 UTC (permalink / raw)
  To: Benjamin Herrenschmidt, Paul Mackerras, Michael Ellerman, segher
  Cc: linuxppc-dev, linux-kernel

call_do_irq() and call_do_softirq() are quite similar on PPC32 and
PPC64 and are simple enough to be worth inlining.

Inlining them avoids an mflr/mtlr pair plus a save/reload on stack.

This is inspired from S390 arch. Several other arches do more or
less the same. The way sparc arch does seems odd thought.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Reviewed-by: Segher Boessenkool <segher@kernel.crashing.org>

---
v2: no change.
v3: no change.
v4:
- comment reminding the purpose of the inline asm block.
- added r2 as clobbered reg
---
 arch/powerpc/include/asm/irq.h |  2 --
 arch/powerpc/kernel/irq.c      | 32 ++++++++++++++++++++++++++++++++
 arch/powerpc/kernel/misc_32.S  | 25 -------------------------
 arch/powerpc/kernel/misc_64.S  | 22 ----------------------
 4 files changed, 32 insertions(+), 49 deletions(-)

diff --git a/arch/powerpc/include/asm/irq.h b/arch/powerpc/include/asm/irq.h
index 0c6469983c66..10476d5283dc 100644
--- a/arch/powerpc/include/asm/irq.h
+++ b/arch/powerpc/include/asm/irq.h
@@ -57,8 +57,6 @@ extern void *mcheckirq_ctx[NR_CPUS];
 extern void *hardirq_ctx[NR_CPUS];
 extern void *softirq_ctx[NR_CPUS];
 
-void call_do_softirq(void *sp);
-void call_do_irq(struct pt_regs *regs, void *sp);
 extern void do_IRQ(struct pt_regs *regs);
 extern void __init init_IRQ(void);
 extern void __do_irq(struct pt_regs *regs);
diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
index 04204be49577..d62fe18405a0 100644
--- a/arch/powerpc/kernel/irq.c
+++ b/arch/powerpc/kernel/irq.c
@@ -642,6 +642,22 @@ void __do_irq(struct pt_regs *regs)
 	irq_exit();
 }
 
+static inline void call_do_irq(struct pt_regs *regs, void *sp)
+{
+	register unsigned long r3 asm("r3") = (unsigned long)regs;
+
+	/* Temporarily switch r1 to sp, call __do_irq() then restore r1 */
+	asm volatile(
+		"	"PPC_STLU"	1, %2(%1);\n"
+		"	mr		1, %1;\n"
+		"	bl		%3;\n"
+		"	"PPC_LL"	1, 0(1);\n" :
+		"+r"(r3) :
+		"b"(sp), "i"(THREAD_SIZE - STACK_FRAME_OVERHEAD), "i"(__do_irq) :
+		"lr", "xer", "ctr", "memory", "cr0", "cr1", "cr5", "cr6", "cr7",
+		"r0", "r2", "r4", "r5", "r6", "r7", "r8", "r9", "r10", "r11", "r12");
+}
+
 void do_IRQ(struct pt_regs *regs)
 {
 	struct pt_regs *old_regs = set_irq_regs(regs);
@@ -686,6 +702,22 @@ void *mcheckirq_ctx[NR_CPUS] __read_mostly;
 void *softirq_ctx[NR_CPUS] __read_mostly;
 void *hardirq_ctx[NR_CPUS] __read_mostly;
 
+static inline void call_do_softirq(const void *sp)
+{
+	register unsigned long ret asm("r3");
+
+	/* Temporarily switch r1 to sp, call __do_softirq() then restore r1 */
+	asm volatile(
+		"	"PPC_STLU"	1, %2(%1);\n"
+		"	mr		1, %1;\n"
+		"	bl		%3;\n"
+		"	"PPC_LL"	1, 0(1);\n" :
+		"=r"(ret) :
+		"b"(sp), "i"(THREAD_SIZE - STACK_FRAME_OVERHEAD), "i"(__do_softirq) :
+		"lr", "xer", "ctr", "memory", "cr0", "cr1", "cr5", "cr6", "cr7",
+		"r0", "r2", "r4", "r5", "r6", "r7", "r8", "r9", "r10", "r11", "r12");
+}
+
 void do_softirq_own_stack(void)
 {
 	void *irqsp = softirq_ctx[smp_processor_id()];
diff --git a/arch/powerpc/kernel/misc_32.S b/arch/powerpc/kernel/misc_32.S
index a5422f7782b3..307307b57743 100644
--- a/arch/powerpc/kernel/misc_32.S
+++ b/arch/powerpc/kernel/misc_32.S
@@ -33,31 +33,6 @@
 
 	.text
 
-_GLOBAL(call_do_softirq)
-	mflr	r0
-	stw	r0,4(r1)
-	stwu	r1,THREAD_SIZE-STACK_FRAME_OVERHEAD(r3)
-	mr	r1,r3
-	bl	__do_softirq
-	lwz	r1,0(r1)
-	lwz	r0,4(r1)
-	mtlr	r0
-	blr
-
-/*
- * void call_do_irq(struct pt_regs *regs, void *sp);
- */
-_GLOBAL(call_do_irq)
-	mflr	r0
-	stw	r0,4(r1)
-	stwu	r1,THREAD_SIZE-STACK_FRAME_OVERHEAD(r4)
-	mr	r1,r4
-	bl	__do_irq
-	lwz	r1,0(r1)
-	lwz	r0,4(r1)
-	mtlr	r0
-	blr
-
 /*
  * This returns the high 64 bits of the product of two 64-bit numbers.
  */
diff --git a/arch/powerpc/kernel/misc_64.S b/arch/powerpc/kernel/misc_64.S
index b55a7b4cb543..69fd714a5236 100644
--- a/arch/powerpc/kernel/misc_64.S
+++ b/arch/powerpc/kernel/misc_64.S
@@ -27,28 +27,6 @@
 
 	.text
 
-_GLOBAL(call_do_softirq)
-	mflr	r0
-	std	r0,16(r1)
-	stdu	r1,THREAD_SIZE-STACK_FRAME_OVERHEAD(r3)
-	mr	r1,r3
-	bl	__do_softirq
-	ld	r1,0(r1)
-	ld	r0,16(r1)
-	mtlr	r0
-	blr
-
-_GLOBAL(call_do_irq)
-	mflr	r0
-	std	r0,16(r1)
-	stdu	r1,THREAD_SIZE-STACK_FRAME_OVERHEAD(r4)
-	mr	r1,r4
-	bl	__do_irq
-	ld	r1,0(r1)
-	ld	r0,16(r1)
-	mtlr	r0
-	blr
-
 	.section	".toc","aw"
 PPC64_CACHES:
 	.tc		ppc64_caches[TC],ppc64_caches
-- 
2.13.3


^ permalink raw reply	[flat|nested] 2+ messages in thread

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2019-10-10  5:36 [PATCH v4 1/2] powerpc/irq: bring back ksp_limit management in C functions Christophe Leroy
2019-10-10  5:36 ` [PATCH v4 2/2] powerpc/irq: inline call_do_irq() and call_do_softirq() Christophe Leroy

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