linux-kernel - Re: [PATCH v3 04/11] x86/irq: Factor out common NMI handling code

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Date: Fri, 28 Jun 2024 17:31:50 -0700
From: Xin Li <xin@...or.com>
To: Jacob Pan <jacob.jun.pan@...ux.intel.com>, X86 Kernel <x86@...nel.org>,
        Sean Christopherson <seanjc@...gle.com>,
        LKML
 <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Dave Hansen <dave.hansen@...el.com>, "H. Peter Anvin" <hpa@...or.com>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Xin Li <xin3.li@...el.com>, linux-perf-users@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>
Cc: Paolo Bonzini <pbonzini@...hat.com>, Tony Luck <tony.luck@...el.com>,
        Andy Lutomirski <luto@...nel.org>, acme@...nel.org,
        kan.liang@...ux.intel.com, Andi Kleen <andi.kleen@...el.com>,
        "Mehta, Sohil" <sohil.mehta@...el.com>
Subject: Re: [PATCH v3 04/11] x86/irq: Factor out common NMI handling code

On 6/28/2024 1:18 PM, Jacob Pan wrote:
> In preparation for handling NMIs with explicit source reporting, factor
> out common code for reuse.
> 

My read is that this patch has no functional change, right?

If yes, please add "No functional change intended."

> Signed-off-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>
> ---
>   arch/x86/kernel/nmi.c | 28 ++++++++++++++++------------
>   1 file changed, 16 insertions(+), 12 deletions(-)
> 
> diff --git a/arch/x86/kernel/nmi.c b/arch/x86/kernel/nmi.c
> index 1ebe93edba7a..639a34e78bc9 100644
> --- a/arch/x86/kernel/nmi.c
> +++ b/arch/x86/kernel/nmi.c
> @@ -135,6 +135,20 @@ static void nmi_check_duration(struct nmiaction *action, u64 duration)
>   		action->handler, duration, decimal_msecs);
>   }
>   
> +static inline int do_handle_nmi(struct nmiaction *a, struct pt_regs *regs, unsigned int type)
> +{
> +	int thishandled;
> +	u64 delta;
> +
> +	delta = sched_clock();
> +	thishandled = a->handler(type, regs);
> +	delta = sched_clock() - delta;
> +	trace_nmi_handler(a->handler, (int)delta, thishandled);
> +	nmi_check_duration(a, delta);
> +
> +	return thishandled;
> +}
> +
>   static int nmi_handle(unsigned int type, struct pt_regs *regs)
>   {
>   	struct nmi_desc *desc = nmi_to_desc(type);
> @@ -149,18 +163,8 @@ static int nmi_handle(unsigned int type, struct pt_regs *regs)
>   	 * can be latched at any given time.  Walk the whole list
>   	 * to handle those situations.
>   	 */
> -	list_for_each_entry_rcu(a, &desc->head, list) {
> -		int thishandled;
> -		u64 delta;
> -
> -		delta = sched_clock();
> -		thishandled = a->handler(type, regs);
> -		handled += thishandled;
> -		delta = sched_clock() - delta;
> -		trace_nmi_handler(a->handler, (int)delta, thishandled);
> -
> -		nmi_check_duration(a, delta);
> -	}
> +	list_for_each_entry_rcu(a, &desc->head, list)
> +		handled += do_handle_nmi(a, regs, type);
>   
>   	rcu_read_unlock();
>   

As this is a preparation patch, better move it earlier before any actual 
NMI source changes, maybe the first patch of this series.

Thanks!
     Xin