From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5C4314438E for ; Fri, 1 Mar 2024 11:33:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709292818; cv=none; b=WG03bUO8eN7r32xRcmFsY1ZpYsDstPhlbZTgp7Zr9whdCpPgBn9irUoZoHmn/yWv/rEMSCM0zyAk9tAe9sQJgFuS+T4toMO7ANdqr8Hbtkg8C0lKksrbz0uISMiltwUN8e61vwXqoUC/btX7Bjbq01RK4k6eqc7VCifonsyNFWY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709292818; c=relaxed/simple; bh=FQMGv7PmATC7VR1MwAuQvuUYpMVWZ8wkTcljl9/Xkqc=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=A9VMfYjpv74Z1/Mu3g1PsmnsBnGkbzeftGwQjjmN37F5VVw3Nucg2ogxItEPQ8furu1wuqM+t2iOrkDR6sJvl2szBOGBXJ5PgHXlgE2j4xlLDAj0nJBNh3CDvjfNRIJ3hX7I6B0IHd3wPlhbKfFjleFBTjPR9thq7SOYcztNWsE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=tHhkWxji; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=11jtywQ/; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="tHhkWxji"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="11jtywQ/" From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1709292814; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=KaJW+PGzJMPU08LMdd6ra/36/s+8KlMVMHUHupu24Eg=; b=tHhkWxjiL3c61ImcYSTznqHlgWNCQnTKobQr4ISvWMHLSdKyqIGYptR9XmejVhx+mO4clg BsUEj1z/J/2pt5d2b3c/qj1a50ycqlnXcNtoYAzOKw/RvITpPZZwz8Loips0sNQU/8vJOD SzpOOQEdUMW2tgDuvQxGpd01+43FphTnHPQR2LsOaFyuMiaL0kDUVv0plu9Ep0mFnNeAta Eh7rVfhNipqbkuSSCnVZwgaAVM42iFWvWzV4QE5Y2t9jK6TLI8Vm9RDaTelyO5ymjMsatX PpO0QK1FNbkrWlZEB0bLnwIM/5UI9gFms2MxG9h6QxEtN4dm7dC/FxGoMw85kw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1709292814; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=KaJW+PGzJMPU08LMdd6ra/36/s+8KlMVMHUHupu24Eg=; b=11jtywQ/wCzJUZQ+4YoHyF3vDjw1g6gaP3O+1SjMhUUl1Zp5GVwZUPFSophNsbooZx9I3E dw+zegdZptEPzpDA== To: LKML Cc: x86@kernel.org, Steven Rostedt , "Paul E. McKenney" Subject: Re: [patch 6/6] x86/idle: Select idle routine only once In-Reply-To: <87h6hq74j0.ffs@tglx> References: <20240229141407.283316443@linutronix.de> <20240229142248.582321500@linutronix.de> <87h6hq74j0.ffs@tglx> Date: Fri, 01 Mar 2024 12:33:33 +0100 Message-ID: <87edcu6vaq.ffs@tglx> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain On Fri, Mar 01 2024 at 09:14, Thomas Gleixner wrote: > On Thu, Feb 29 2024 at 15:23, Thomas Gleixner wrote: >> >> - if (x86_idle_set()) >> - return; >> - > > Bah. With XEN=n this results in a defined but not used warning. > Updated version below. I'm a moron. xen_set_default_idle() is invoked very early on, so select_idle_routine() has to keep the check. Sigh. Fixed it and added an comment to that effect. --- Subject: x86/idle: Select idle routine only once From: Thomas Gleixner Date: Wed, 28 Feb 2024 23:20:32 +0100 The idle routine selection is done on every CPU bringup operation and has a guard in place which is effective after the first invocation, which is a pointless exercise. Invoke it once on the boot CPU and mark the related functions __init. The guard check has to stay as xen_set_default_idle() runs early. Signed-off-by: Thomas Gleixner --- V1b: Keep the x86_idle_set() check so XEN keeps working V1a: Move x86_idle_set() into the only usage site (0day) --- arch/x86/include/asm/processor.h | 2 +- arch/x86/kernel/cpu/common.c | 4 ++-- arch/x86/kernel/process.c | 8 +++++--- 3 files changed, 8 insertions(+), 6 deletions(-) --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -555,7 +555,7 @@ static inline void load_sp0(unsigned lon unsigned long __get_wchan(struct task_struct *p); -extern void select_idle_routine(const struct cpuinfo_x86 *c); +extern void select_idle_routine(void); extern void amd_e400_c1e_apic_setup(void); extern unsigned long boot_option_idle_override; --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -1938,8 +1938,6 @@ static void identify_cpu(struct cpuinfo_ /* Init Machine Check Exception if available. */ mcheck_cpu_init(c); - select_idle_routine(c); - #ifdef CONFIG_NUMA numa_add_cpu(smp_processor_id()); #endif @@ -2343,6 +2341,8 @@ void __init arch_cpu_finalize_init(void) { identify_boot_cpu(); + select_idle_routine(); + /* * identify_boot_cpu() initialized SMT support information, let the * core code know. --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -853,8 +853,9 @@ void __noreturn stop_this_cpu(void *dumm * Do not prefer MWAIT if MONITOR instruction has a bug or idle=nomwait * is passed to kernel commandline parameter. */ -static bool prefer_mwait_c1_over_halt(const struct cpuinfo_x86 *c) +static __init bool prefer_mwait_c1_over_halt(void) { + const struct cpuinfo_x86 *c = &boot_cpu_data; u32 eax, ebx, ecx, edx; /* If override is enforced on the command line, fall back to HALT. */ @@ -908,7 +909,7 @@ static __cpuidle void mwait_idle(void) __current_clr_polling(); } -void select_idle_routine(const struct cpuinfo_x86 *c) +void __init select_idle_routine(void) { if (boot_option_idle_override == IDLE_POLL) { if (IS_ENABLED(CONFIG_SMP) && smp_num_siblings > 1) @@ -916,10 +917,11 @@ void select_idle_routine(const struct cp return; } + /* Required to guard against xen_set_default_idle() */ if (x86_idle_set()) return; - if (prefer_mwait_c1_over_halt(c)) { + if (prefer_mwait_c1_over_halt()) { pr_info("using mwait in idle threads\n"); static_call_update(x86_idle, mwait_idle); } else if (cpu_feature_enabled(X86_FEATURE_TDX_GUEST)) {