linux-kernel - Re: [patch 6/8] x86/entry: Move irq tracing to syscall_slow_exit

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Date:   Thu, 27 Feb 2020 17:12:19 +0100
From:   Alexandre Chartre <alexandre.chartre@...cle.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>
Cc:     x86@...nel.org, Steven Rostedt <rostedt@...dmis.org>,
        Brian Gerst <brgerst@...il.com>,
        Juergen Gross <jgross@...e.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: [patch 6/8] x86/entry: Move irq tracing to syscall_slow_exit_work


On 2/25/20 11:08 PM, Thomas Gleixner wrote:
> which removes the ASM IRQ tracepoints.

This moves irq tracing to syscall_return_slowpath, not syscall_slow_exit_work,
right?

alex.

  
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> ---
>   arch/x86/entry/common.c   |    2 ++
>   arch/x86/entry/entry_32.S |    3 ++-
>   arch/x86/entry/entry_64.S |    3 ---
>   3 files changed, 4 insertions(+), 4 deletions(-)
> 
> --- a/arch/x86/entry/common.c
> +++ b/arch/x86/entry/common.c
> @@ -299,6 +299,8 @@ static void syscall_slow_exit_work(struc
>   
>   	local_irq_disable();
>   	__prepare_exit_to_usermode(regs);
> +	/* Return to user space enables interrupts */
> +	trace_hardirqs_on();
>   }
>   NOKPROBE_SYMBOL(syscall_return_slowpath);
>   
> --- a/arch/x86/entry/entry_32.S
> +++ b/arch/x86/entry/entry_32.S
> @@ -812,7 +812,7 @@ SYM_CODE_START(ret_from_fork)
>   	movl    %esp, %eax
>   	call    syscall_return_slowpath
>   	STACKLEAK_ERASE
> -	jmp     restore_all
> +	jmp     restore_all_switch_stack
>   
>   	/* kernel thread */
>   1:	movl	%edi, %eax
> @@ -1077,6 +1077,7 @@ SYM_FUNC_START(entry_INT80_32)
>   
>   restore_all:
>   	TRACE_IRQS_IRET
> +restore_all_switch_stack:
>   	SWITCH_TO_ENTRY_STACK
>   	CHECK_AND_APPLY_ESPFIX
>   .Lrestore_nocheck:
> --- a/arch/x86/entry/entry_64.S
> +++ b/arch/x86/entry/entry_64.S
> @@ -172,8 +172,6 @@ SYM_INNER_LABEL(entry_SYSCALL_64_after_h
>   	movq	%rsp, %rsi
>   	call	do_syscall_64		/* returns with IRQs disabled */
>   
> -	TRACE_IRQS_ON			/* return enables interrupts */
> -
>   	/*
>   	 * Try to use SYSRET instead of IRET if we're returning to
>   	 * a completely clean 64-bit userspace context.  If we're not,
> @@ -340,7 +338,6 @@ SYM_CODE_START(ret_from_fork)
>   	UNWIND_HINT_REGS
>   	movq	%rsp, %rdi
>   	call	syscall_return_slowpath	/* returns with IRQs disabled */
> -	TRACE_IRQS_ON			/* user mode is traced as IRQS on */
>   	jmp	swapgs_restore_regs_and_return_to_usermode
>   
>   1:
>