linux-kernel - Re: [PATCH v2] x86/apic: Inline __x2apic_send_IPI

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Message-ID: <CANn89iJ1rNMS7ud6eCd1p=Wkr2eMsGTFrJ5-RSPROKWET00vMw@mail.gmail.com>
Date: Tue, 20 Jan 2026 10:16:11 +0100
From: Eric Dumazet <edumazet@...gle.com>
To: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, 
	"H . Peter Anvin" <hpa@...or.com>
Cc: linux-kernel <linux-kernel@...r.kernel.org>, Eric Dumazet <eric.dumazet@...il.com>
Subject: Re: [PATCH v2] x86/apic: Inline __x2apic_send_IPI_dest()

On Tue, Dec 23, 2025 at 6:20 AM Eric Dumazet <edumazet@...gle.com> wrote:
>
> Avoid one call/ret in networking RPS/RFS fast path, with no space cost.
>
> scripts/bloat-o-meter -t vmlinux.before vmlinux.after
> add/remove: 0/2 grow/shrink: 2/0 up/down: 96/-97 (-1)
> Function                                     old     new   delta
> x2apic_send_IPI                              146     198     +52
> __x2apic_send_IPI_mask                       326     370     +44
> __pfx___x2apic_send_IPI_dest                  16       -     -16
> __x2apic_send_IPI_dest                        81       -     -81
> Total: Before=20861234, After=20861233, chg -0.00%
>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> ---
> v2: added CONFIG_X86_X2APIC dependency (kernel test robot), updated bloat-o-meter
> v1: https://lore.kernel.org/lkml/CANn89iJ4r5hrqE=Lj16XVNFM7iZ+XB+JsXU8gE5ryeuG6kf1Sg@mail.gmail.com/T/#mc7288459ec504831a9888cb0e5c4dbdae253f263
>
>  arch/x86/kernel/apic/local.h       | 10 +++++++++-
>  arch/x86/kernel/apic/x2apic_phys.c |  6 ------
>  2 files changed, 9 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/kernel/apic/local.h b/arch/x86/kernel/apic/local.h
> index bdcf609eb283..0e5dd6772d6a 100644
> --- a/arch/x86/kernel/apic/local.h
> +++ b/arch/x86/kernel/apic/local.h
> @@ -14,7 +14,6 @@
>  #include <asm/apic.h>
>
>  /* X2APIC */
> -void __x2apic_send_IPI_dest(unsigned int apicid, int vector, unsigned int dest);
>  u32 x2apic_get_apic_id(u32 id);
>
>  void x2apic_send_IPI_all(int vector);
> @@ -42,6 +41,15 @@ static inline unsigned int __prepare_ICR(unsigned int shortcut, int vector,
>         return icr;
>  }
>
> +#ifdef CONFIG_X86_X2APIC
> +static inline void __x2apic_send_IPI_dest(unsigned int apicid, int vector,
> +                                         unsigned int dest)
> +{
> +       unsigned long cfg = __prepare_ICR(0, vector, dest);
> +       native_x2apic_icr_write(cfg, apicid);
> +}
> +#endif
> +
>  void default_init_apic_ldr(void);
>
>  void apic_mem_wait_icr_idle(void);
> diff --git a/arch/x86/kernel/apic/x2apic_phys.c b/arch/x86/kernel/apic/x2apic_phys.c
> index 12d4c35547a6..10f79026e8e3 100644
> --- a/arch/x86/kernel/apic/x2apic_phys.c
> +++ b/arch/x86/kernel/apic/x2apic_phys.c
> @@ -107,12 +107,6 @@ void x2apic_send_IPI_self(int vector)
>         apic_write(APIC_SELF_IPI, vector);
>  }
>
> -void __x2apic_send_IPI_dest(unsigned int apicid, int vector, unsigned int dest)
> -{
> -       unsigned long cfg = __prepare_ICR(0, vector, dest);
> -       native_x2apic_icr_write(cfg, apicid);
> -}
> -
>  static int x2apic_phys_probe(void)
>  {
>         if (!x2apic_mode)
> --
> 2.52.0.351.gbe84eed79e-goog
>

I do not think I received any feedback for this patch, should I resend it ?

Thanks.