[PATCH v7] powerpc/irq: Inline call_do_irq() and call_do_softirq()

Michael Ellerman mpe at ellerman.id.au
Sat Mar 20 23:22:27 AEDT 2021


From: Christophe Leroy <christophe.leroy at csgroup.eu>

call_do_irq() and call_do_softirq() are simple enough to be
worth inlining.

Inlining them avoids an mflr/mtlr pair plus a save/reload on stack. It
also allows GCC to keep the saved ksp_limit in an nonvolatile reg.

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 at csgroup.eu>
Signed-off-by: Michael Ellerman <mpe at ellerman.id.au>
---

v2: no change.
v3: no change.
v4:
- comment reminding the purpose of the inline asm block.
- added r2 as clobbered reg
v5:
- Limiting the change to PPC32 for now.
- removed r2 from the clobbered regs list (on PPC32 r2 points to current all the time)
- Removed patch 1 and merged ksp_limit handling in here.
v6:
- Rebase on top of merge-test (ca6e327fefb2).
- Remove the ksp_limit stuff as it's doesn't exist anymore.

v7:
mpe:
- Enable for 64-bit too. This all in-kernel code calling in-kernel
  code, and must use the kernel TOC.
- Use named parameters for the inline asm.
- Reformat inline asm.
- Mark as always_inline.
- Drop unused ret from call_do_softirq(), add r3 as clobbered.
---
 arch/powerpc/include/asm/irq.h |  2 --
 arch/powerpc/kernel/irq.c      | 41 ++++++++++++++++++++++++++++++++++
 arch/powerpc/kernel/misc_32.S  | 25 ---------------------
 arch/powerpc/kernel/misc_64.S  | 22 ------------------
 4 files changed, 41 insertions(+), 49 deletions(-)

diff --git a/arch/powerpc/include/asm/irq.h b/arch/powerpc/include/asm/irq.h
index f3f264e441a7..b2bd58830430 100644
--- a/arch/powerpc/include/asm/irq.h
+++ b/arch/powerpc/include/asm/irq.h
@@ -53,8 +53,6 @@ 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 5b72abbff96c..260effc0a435 100644
--- a/arch/powerpc/kernel/irq.c
+++ b/arch/powerpc/kernel/irq.c
@@ -667,6 +667,47 @@ static inline void check_stack_overflow(void)
 	}
 }
 
+static __always_inline void call_do_softirq(const void *sp)
+{
+	/* Temporarily switch r1 to sp, call __do_softirq() then restore r1. */
+	asm volatile (
+		 PPC_STLU "	%%r1, %[offset](%[sp])	;"
+		"mr		%%r1, %[sp]		;"
+		"bl		%[callee]		;"
+		 PPC_LL "	%%r1, 0(%%r1)		;"
+		 : // Outputs
+		 : // Inputs
+		   [sp] "b" (sp), [offset] "i" (THREAD_SIZE - STACK_FRAME_OVERHEAD),
+		   [callee] "i" (__do_softirq)
+		 : // Clobbers
+		   "lr", "xer", "ctr", "memory", "cr0", "cr1", "cr5", "cr6",
+		   "cr7", "r0", "r3", "r4", "r5", "r6", "r7", "r8", "r9", "r10",
+		   "r11", "r12"
+	);
+}
+
+static __always_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 "	%%r1, %[offset](%[sp])	;"
+		"mr		%%r1, %[sp]		;"
+		"bl		%[callee]		;"
+		 PPC_LL "	%%r1, 0(%%r1)		;"
+		 : // Outputs
+		   "+r" (r3)
+		 : // Inputs
+		   [sp] "b" (sp), [offset] "i" (THREAD_SIZE - STACK_FRAME_OVERHEAD),
+		   [callee] "i" (__do_irq)
+		 : // Clobbers
+		   "lr", "xer", "ctr", "memory", "cr0", "cr1", "cr5", "cr6",
+		   "cr7", "r0", "r4", "r5", "r6", "r7", "r8", "r9", "r10",
+		   "r11", "r12"
+	);
+}
+
 void __do_irq(struct pt_regs *regs)
 {
 	unsigned int irq;
diff --git a/arch/powerpc/kernel/misc_32.S b/arch/powerpc/kernel/misc_32.S
index acc410043b96..6a076bef2932 100644
--- a/arch/powerpc/kernel/misc_32.S
+++ b/arch/powerpc/kernel/misc_32.S
@@ -27,31 +27,6 @@
 
 	.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 070465825c21..4b761a18a74d 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
-
 _GLOBAL(__bswapdi2)
 EXPORT_SYMBOL(__bswapdi2)
 	srdi	r8,r3,32
-- 
2.25.1



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