[PATCH] powerpc: Remove MSR_PR check in interrupt_exit_{user/kernel}_prepare()

Subsystems: linux for powerpc (32-bit and 64-bit), the rest

STALE1833d

4 messages, 2 authors, 2021-08-04 · open the first message on its own page

[PATCH] powerpc: Remove MSR_PR check in interrupt_exit_{user/kernel}_prepare()

From: Christophe Leroy <hidden>
Date: 2021-08-04 05:28:00

In those hot functions that are called at every interrupt, any saved
cycle is worth it.

interrupt_exit_user_prepare() and interrupt_exit_kernel_prepare() are
called from three places:
- From entry_32.S
- From interrupt_64.S
- From interrupt_exit_user_restart() and interrupt_exit_kernel_restart()

In entry_32.S, there are inambiguously called based on MSR_PR:

	interrupt_return:
		lwz	r4,_MSR(r1)
		addi	r3,r1,STACK_FRAME_OVERHEAD
		andi.	r0,r4,MSR_PR
		beq	.Lkernel_interrupt_return
		bl	interrupt_exit_user_prepare
	...
	.Lkernel_interrupt_return:
		bl	interrupt_exit_kernel_prepare

In interrupt_64.S, that's similar:

	interrupt_return_\srr\():
		ld	r4,_MSR(r1)
		andi.	r0,r4,MSR_PR
		beq	interrupt_return_\srr\()_kernel
	interrupt_return_\srr\()_user: /* make backtraces match the _kernel variant */
		addi	r3,r1,STACK_FRAME_OVERHEAD
		bl	interrupt_exit_user_prepare
	...
	interrupt_return_\srr\()_kernel:
		addi	r3,r1,STACK_FRAME_OVERHEAD
		bl	interrupt_exit_kernel_prepare

In interrupt_exit_user_restart() and interrupt_exit_kernel_restart(),
MSR_PR is verified respectively by BUG_ON(!user_mode(regs)) and
BUG_ON(user_mode(regs)) prior to calling interrupt_exit_user_prepare()
and interrupt_exit_kernel_prepare().

The verification in interrupt_exit_user_prepare() and
interrupt_exit_kernel_prepare() are therefore useless and can be removed.

Signed-off-by: Christophe Leroy <redacted>
---
 arch/powerpc/kernel/interrupt.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/arch/powerpc/kernel/interrupt.c b/arch/powerpc/kernel/interrupt.c
index 21bbd615ca41..f26caf911ab5 100644
--- a/arch/powerpc/kernel/interrupt.c
+++ b/arch/powerpc/kernel/interrupt.c

@@ -465,7 +465,6 @@ notrace unsigned long interrupt_exit_user_prepare(struct pt_regs *regs)
 
 	if (!IS_ENABLED(CONFIG_BOOKE) && !IS_ENABLED(CONFIG_40x))
 		BUG_ON(!(regs->msr & MSR_RI));
-	BUG_ON(!(regs->msr & MSR_PR));
 	BUG_ON(arch_irq_disabled_regs(regs));
 	CT_WARN_ON(ct_state() == CONTEXT_USER);

@@ -499,7 +498,6 @@ notrace unsigned long interrupt_exit_kernel_prepare(struct pt_regs *regs)
 	if (!IS_ENABLED(CONFIG_BOOKE) && !IS_ENABLED(CONFIG_40x) &&
 	    unlikely(!(regs->msr & MSR_RI)))
 		unrecoverable_exception(regs);
-	BUG_ON(regs->msr & MSR_PR);
 	/*
 	 * CT_WARN_ON comes here via program_check_exception,
 	 * so avoid recursion.

-- 
2.25.0

Re: [PATCH] powerpc: Remove MSR_PR check in interrupt_exit_{user/kernel}_prepare()

From: Nicholas Piggin <npiggin@gmail.com>
Date: 2021-08-04 08:08:24

Excerpts from Christophe Leroy's message of August 4, 2021 3:27 pm:

In those hot functions that are called at every interrupt, any saved
cycle is worth it.

interrupt_exit_user_prepare() and interrupt_exit_kernel_prepare() are
called from three places:
- From entry_32.S
- From interrupt_64.S
- From interrupt_exit_user_restart() and interrupt_exit_kernel_restart()

In entry_32.S, there are inambiguously called based on MSR_PR:

	interrupt_return:
		lwz	r4,_MSR(r1)
		addi	r3,r1,STACK_FRAME_OVERHEAD
		andi.	r0,r4,MSR_PR
		beq	.Lkernel_interrupt_return
		bl	interrupt_exit_user_prepare
	...
	.Lkernel_interrupt_return:
		bl	interrupt_exit_kernel_prepare

In interrupt_64.S, that's similar:

	interrupt_return_\srr\():
		ld	r4,_MSR(r1)
		andi.	r0,r4,MSR_PR
		beq	interrupt_return_\srr\()_kernel
	interrupt_return_\srr\()_user: /* make backtraces match the _kernel variant */
		addi	r3,r1,STACK_FRAME_OVERHEAD
		bl	interrupt_exit_user_prepare
	...
	interrupt_return_\srr\()_kernel:
		addi	r3,r1,STACK_FRAME_OVERHEAD
		bl	interrupt_exit_kernel_prepare

In interrupt_exit_user_restart() and interrupt_exit_kernel_restart(),
MSR_PR is verified respectively by BUG_ON(!user_mode(regs)) and
BUG_ON(user_mode(regs)) prior to calling interrupt_exit_user_prepare()
and interrupt_exit_kernel_prepare().

The verification in interrupt_exit_user_prepare() and
interrupt_exit_kernel_prepare() are therefore useless and can be removed.

Signed-off-by: Christophe Leroy <redacted>

Probably okay to do now things are ironing out.

Unless we want to make a new define for interrupt handler debug and put 
a bunch of these asserts under it. There's quite a lot more here, and
in asm/interrupt.h, etc.

Thanks,
Nick

quoted hunk

---
 arch/powerpc/kernel/interrupt.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/arch/powerpc/kernel/interrupt.c b/arch/powerpc/kernel/interrupt.c
index 21bbd615ca41..f26caf911ab5 100644
--- a/arch/powerpc/kernel/interrupt.c
+++ b/arch/powerpc/kernel/interrupt.c

@@ -465,7 +465,6 @@ notrace unsigned long interrupt_exit_user_prepare(struct pt_regs *regs)
 
 	if (!IS_ENABLED(CONFIG_BOOKE) && !IS_ENABLED(CONFIG_40x))
 		BUG_ON(!(regs->msr & MSR_RI));
-	BUG_ON(!(regs->msr & MSR_PR));
 	BUG_ON(arch_irq_disabled_regs(regs));
 	CT_WARN_ON(ct_state() == CONTEXT_USER);

@@ -499,7 +498,6 @@ notrace unsigned long interrupt_exit_kernel_prepare(struct pt_regs *regs)
 	if (!IS_ENABLED(CONFIG_BOOKE) && !IS_ENABLED(CONFIG_40x) &&
 	    unlikely(!(regs->msr & MSR_RI)))
 		unrecoverable_exception(regs);
-	BUG_ON(regs->msr & MSR_PR);
 	/*
 	 * CT_WARN_ON comes here via program_check_exception,
 	 * so avoid recursion.

-- 
2.25.0

Re: [PATCH] powerpc: Remove MSR_PR check in interrupt_exit_{user/kernel}_prepare()

From: Christophe Leroy <hidden>
Date: 2021-08-04 08:37:16


Le 04/08/2021 à 10:08, Nicholas Piggin a écrit :

Excerpts from Christophe Leroy's message of August 4, 2021 3:27 pm:

quoted

In those hot functions that are called at every interrupt, any saved
cycle is worth it.

interrupt_exit_user_prepare() and interrupt_exit_kernel_prepare() are
called from three places:
- From entry_32.S
- From interrupt_64.S
- From interrupt_exit_user_restart() and interrupt_exit_kernel_restart()

In entry_32.S, there are inambiguously called based on MSR_PR:

	interrupt_return:
		lwz	r4,_MSR(r1)
		addi	r3,r1,STACK_FRAME_OVERHEAD
		andi.	r0,r4,MSR_PR
		beq	.Lkernel_interrupt_return
		bl	interrupt_exit_user_prepare
	...
	.Lkernel_interrupt_return:
		bl	interrupt_exit_kernel_prepare

In interrupt_64.S, that's similar:

	interrupt_return_\srr\():
		ld	r4,_MSR(r1)
		andi.	r0,r4,MSR_PR
		beq	interrupt_return_\srr\()_kernel
	interrupt_return_\srr\()_user: /* make backtraces match the _kernel variant */
		addi	r3,r1,STACK_FRAME_OVERHEAD
		bl	interrupt_exit_user_prepare
	...
	interrupt_return_\srr\()_kernel:
		addi	r3,r1,STACK_FRAME_OVERHEAD
		bl	interrupt_exit_kernel_prepare

In interrupt_exit_user_restart() and interrupt_exit_kernel_restart(),
MSR_PR is verified respectively by BUG_ON(!user_mode(regs)) and
BUG_ON(user_mode(regs)) prior to calling interrupt_exit_user_prepare()
and interrupt_exit_kernel_prepare().

The verification in interrupt_exit_user_prepare() and
interrupt_exit_kernel_prepare() are therefore useless and can be removed.

Signed-off-by: Christophe Leroy <redacted>

Probably okay to do now things are ironing out.

Unless we want to make a new define for interrupt handler debug and put
a bunch of these asserts under it. There's quite a lot more here, and
in asm/interrupt.h, etc.

But that one is so trivial that I'm not sure there is any point in keeping it even as a kind of 
additional DEBUG level, unless you want those BUG_ONs because you don't trust the compiler.

Christophe

Thanks,
Nick

quoted

---
  arch/powerpc/kernel/interrupt.c | 2 --
  1 file changed, 2 deletions(-)

diff --git a/arch/powerpc/kernel/interrupt.c b/arch/powerpc/kernel/interrupt.c
index 21bbd615ca41..f26caf911ab5 100644
--- a/arch/powerpc/kernel/interrupt.c
+++ b/arch/powerpc/kernel/interrupt.c

@@ -465,7 +465,6 @@ notrace unsigned long interrupt_exit_user_prepare(struct pt_regs *regs)
  
  	if (!IS_ENABLED(CONFIG_BOOKE) && !IS_ENABLED(CONFIG_40x))
  		BUG_ON(!(regs->msr & MSR_RI));
-	BUG_ON(!(regs->msr & MSR_PR));
  	BUG_ON(arch_irq_disabled_regs(regs));
  	CT_WARN_ON(ct_state() == CONTEXT_USER);

@@ -499,7 +498,6 @@ notrace unsigned long interrupt_exit_kernel_prepare(struct pt_regs *regs)
  	if (!IS_ENABLED(CONFIG_BOOKE) && !IS_ENABLED(CONFIG_40x) &&
  	    unlikely(!(regs->msr & MSR_RI)))
  		unrecoverable_exception(regs);
-	BUG_ON(regs->msr & MSR_PR);
  	/*
  	 * CT_WARN_ON comes here via program_check_exception,
  	 * so avoid recursion.

-- 
2.25.0

Re: [PATCH] powerpc: Remove MSR_PR check in interrupt_exit_{user/kernel}_prepare()

From: Nicholas Piggin <npiggin@gmail.com>
Date: 2021-08-04 08:53:56

Excerpts from Christophe Leroy's message of August 4, 2021 6:37 pm:


Le 04/08/2021 à 10:08, Nicholas Piggin a écrit :

quoted

Excerpts from Christophe Leroy's message of August 4, 2021 3:27 pm:

quoted

In those hot functions that are called at every interrupt, any saved
cycle is worth it.

interrupt_exit_user_prepare() and interrupt_exit_kernel_prepare() are
called from three places:
- From entry_32.S
- From interrupt_64.S
- From interrupt_exit_user_restart() and interrupt_exit_kernel_restart()

In entry_32.S, there are inambiguously called based on MSR_PR:

	interrupt_return:
		lwz	r4,_MSR(r1)
		addi	r3,r1,STACK_FRAME_OVERHEAD
		andi.	r0,r4,MSR_PR
		beq	.Lkernel_interrupt_return
		bl	interrupt_exit_user_prepare
	...
	.Lkernel_interrupt_return:
		bl	interrupt_exit_kernel_prepare

In interrupt_64.S, that's similar:

	interrupt_return_\srr\():
		ld	r4,_MSR(r1)
		andi.	r0,r4,MSR_PR
		beq	interrupt_return_\srr\()_kernel
	interrupt_return_\srr\()_user: /* make backtraces match the _kernel variant */
		addi	r3,r1,STACK_FRAME_OVERHEAD
		bl	interrupt_exit_user_prepare
	...
	interrupt_return_\srr\()_kernel:
		addi	r3,r1,STACK_FRAME_OVERHEAD
		bl	interrupt_exit_kernel_prepare

In interrupt_exit_user_restart() and interrupt_exit_kernel_restart(),
MSR_PR is verified respectively by BUG_ON(!user_mode(regs)) and
BUG_ON(user_mode(regs)) prior to calling interrupt_exit_user_prepare()
and interrupt_exit_kernel_prepare().

The verification in interrupt_exit_user_prepare() and
interrupt_exit_kernel_prepare() are therefore useless and can be removed.

Signed-off-by: Christophe Leroy <redacted>

Probably okay to do now things are ironing out.

Unless we want to make a new define for interrupt handler debug and put
a bunch of these asserts under it. There's quite a lot more here, and
in asm/interrupt.h, etc.

But that one is so trivial that I'm not sure there is any point in keeping it even as a kind of 
additional DEBUG level, unless you want those BUG_ONs because you don't trust the compiler.

Fair point.

Acked-by: Nicholas Piggin <npiggin@gmail.com>

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