linux-kernel - Re: [PATCH v4 02/21] x86/hw_breakpoint: Add arch_reinstall_hw

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Message-Id: <20250914225306.2185b79065e32f60a40ef54c@kernel.org>
Date: Sun, 14 Sep 2025 22:53:06 +0900
From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
To: Jinchao Wang <wangjinchao600@...il.com>
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Subject: Re: [PATCH v4 02/21] x86/hw_breakpoint: Add
 arch_reinstall_hw_breakpoint

On Fri, 12 Sep 2025 18:11:12 +0800
Jinchao Wang <wangjinchao600@...il.com> wrote:

> The new arch_reinstall_hw_breakpoint() function can be used in an
> atomic context, unlike the more expensive free and re-allocation path.
> This allows callers to efficiently re-establish an existing breakpoint.
> 

Looks good to me.

Reviewed-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>

Thanks!

> Signed-off-by: Jinchao Wang <wangjinchao600@...il.com>
> ---
>  arch/x86/include/asm/hw_breakpoint.h | 2 ++
>  arch/x86/kernel/hw_breakpoint.c      | 9 +++++++++
>  2 files changed, 11 insertions(+)
> 
> diff --git a/arch/x86/include/asm/hw_breakpoint.h b/arch/x86/include/asm/hw_breakpoint.h
> index aa6adac6c3a2..c22cc4e87fc5 100644
> --- a/arch/x86/include/asm/hw_breakpoint.h
> +++ b/arch/x86/include/asm/hw_breakpoint.h
> @@ -21,6 +21,7 @@ struct arch_hw_breakpoint {
>  
>  enum bp_slot_action {
>  	BP_SLOT_ACTION_INSTALL,
> +	BP_SLOT_ACTION_REINSTALL,
>  	BP_SLOT_ACTION_UNINSTALL,
>  };
>  
> @@ -65,6 +66,7 @@ extern int hw_breakpoint_exceptions_notify(struct notifier_block *unused,
>  
>  
>  int arch_install_hw_breakpoint(struct perf_event *bp);
> +int arch_reinstall_hw_breakpoint(struct perf_event *bp);
>  void arch_uninstall_hw_breakpoint(struct perf_event *bp);
>  void hw_breakpoint_pmu_read(struct perf_event *bp);
>  void hw_breakpoint_pmu_unthrottle(struct perf_event *bp);
> diff --git a/arch/x86/kernel/hw_breakpoint.c b/arch/x86/kernel/hw_breakpoint.c
> index 3658ace4bd8d..29c9369264d4 100644
> --- a/arch/x86/kernel/hw_breakpoint.c
> +++ b/arch/x86/kernel/hw_breakpoint.c
> @@ -99,6 +99,10 @@ static int manage_bp_slot(struct perf_event *bp, enum bp_slot_action action)
>  		old_bp = NULL;
>  		new_bp = bp;
>  		break;
> +	case BP_SLOT_ACTION_REINSTALL:
> +		old_bp = bp;
> +		new_bp = bp;
> +		break;
>  	case BP_SLOT_ACTION_UNINSTALL:
>  		old_bp = bp;
>  		new_bp = NULL;
> @@ -187,6 +191,11 @@ int arch_install_hw_breakpoint(struct perf_event *bp)
>  	return arch_manage_bp(bp, BP_SLOT_ACTION_INSTALL);
>  }
>  
> +int arch_reinstall_hw_breakpoint(struct perf_event *bp)
> +{
> +	return arch_manage_bp(bp, BP_SLOT_ACTION_REINSTALL);
> +}
> +
>  void arch_uninstall_hw_breakpoint(struct perf_event *bp)
>  {
>  	arch_manage_bp(bp, BP_SLOT_ACTION_UNINSTALL);
> -- 
> 2.43.0
> 
> 

-- 
Masami Hiramatsu (Google) <mhiramat@...nel.org>