Re: [PATCH v4 02/21] x86/hw_breakpoint: Add arch_reinstall_hw_breakpoint

Masami Hiramatsu
2025-09-14T13:53:20Z

On Fri, 12 Sep 2025 18:11:12 +0800
Jinchao Wang <wangjinchao600@gmail.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@kernel.org>

Thanks!

> Signed-off-by: Jinchao Wang <wangjinchao600@gmail.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@kernel.org>