From patchwork Wed May 28 12:53:50 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Rafael J. Wysocki" X-Patchwork-Id: 893086 Received: from cloudserver094114.home.pl (cloudserver094114.home.pl [79.96.170.134]) (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 359D220B81D; Wed, 28 May 2025 13:59:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=79.96.170.134 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1748440791; cv=none; b=RvCx9Sxn0FuxKe4sHf3BbFJEbT/gOOTL+OAVuPO9+t7MFvUdh7SovhX3Z258KrgDEdcVrExf41OXf0LPFVmGJxMSNKpiT8+frtODffUVChUhC8fmnTrxxiBuQkdedTAQL/X1nsWMf2F4vH/2Hyq3pFte2ukZg8PuM6nRFRU7HP4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1748440791; c=relaxed/simple; bh=GidpZsTdS1mvFVZhMXx5AjlxUimuu/0oP04bsW6NDt0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=mhJNEsdq6cpUXXqLdqx/J/+WTaMh6l/k3dWRyB6O7dk/CCAKY0hx0THVKFaYBOoEihRtlN+ajYAtG+M3HSR3036ISOQU1DcMRVL4xGPYfxoBTwUfuHA5kVyW8XTjZHNfsxNvz7zeTXKUI+BQzKzAdG4uds6oYFd4RHUk2jOSjKI= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=rjwysocki.net; spf=pass smtp.mailfrom=rjwysocki.net; dkim=pass (2048-bit key) header.d=rjwysocki.net header.i=@rjwysocki.net header.b=qYmj06y/; arc=none smtp.client-ip=79.96.170.134 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=rjwysocki.net Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=rjwysocki.net Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=rjwysocki.net header.i=@rjwysocki.net header.b="qYmj06y/" Received: from kreacher.localnet (unknown [5.63.189.50]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by cloudserver094114.home.pl (Postfix) with ESMTPSA id 9073266808C; Wed, 28 May 2025 14:55:02 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=rjwysocki.net; s=dkim; t=1748436903; bh=GidpZsTdS1mvFVZhMXx5AjlxUimuu/0oP04bsW6NDt0=; h=From:Subject:Date; b=qYmj06y/nV3RBN8Fv+zAmh9NV3LKKLHOdDrbzBcaDhQk9MDi3ifDcpMHQf2gsJgek va06FTPQm6czxhfAXhJ6WxME+BD34MwmG8DevcNaiMgfRZa/ezDUWxFCwGJTI/HOnj kf0+6YiXxdlZvGeiiH7CrwKyE/O0xkEIlP1SOEf4MBI2gZjRWPmVxrbyyW9C+c9+bj aIFguT8ukNOiietqjHyMz026EP+tod/MoqpJ5uk3eC+5LRELvPlu0hkd7xa2HWTRi2 ezbpKTmMfUk13XcC1fy4rc8f6m220KAG2RRJVZKdwDsWgyuTRg/BoxkcyaWLYkEizQ ntoe97QkZcv0w== From: "Rafael J. Wysocki" To: x86 Maintainers Cc: LKML , Linux PM , Len Brown , Peter Zijlstra , Thomas Gleixner , Borislav Petkov , Dave Hansen , Artem Bityutskiy , "Gautham R. Shenoy" , Ingo Molnar , Todd Brandt Subject: [PATCH v1 1/2] Revert "x86/smp: Eliminate mwait_play_dead_cpuid_hint()" Date: Wed, 28 May 2025 14:53:50 +0200 Message-ID: <7811828.EvYhyI6sBW@rjwysocki.net> In-Reply-To: <2006806.PYKUYFuaPT@rjwysocki.net> References: <2006806.PYKUYFuaPT@rjwysocki.net> Precedence: bulk X-Mailing-List: linux-pm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-CLIENT-IP: 5.63.189.50 X-CLIENT-HOSTNAME: 5.63.189.50 X-VADE-SPAMSTATE: clean X-VADE-SPAMCAUSE: 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 X-DCC--Metrics: v370.home.net.pl 1024; Body=12 Fuz1=12 Fuz2=12 From: "Rafael J. Wysocki" Revert commit 96040f7273e2 ("x86/smp: Eliminate mwait_play_dead_cpuid_hint()") because it introduced a significant power regression on systems that start with "nosmt" in the kernel command line. Namely, on such systems, SMT siblings permanently go offline early, when cpuidle has not been initialized yet, so after the above commit, hlt_play_dead() is called for them. Later on, when the processor attempts to enter a deep package C-state, including PC10 which is requisite for reaching minimum power in suspend-to-idle, it is not able to do that because of the SMT siblings staying in C1 (which they have been put into by HLT). Fixes: 96040f7273e2 ("x86/smp: Eliminate mwait_play_dead_cpuid_hint()") Reported-by: Todd Brandt Tested-by: Todd Brandt Cc: 6.15+ # 6.15+ Signed-off-by: Rafael J. Wysocki --- arch/x86/kernel/smpboot.c | 54 ++++++++++++++++++++++++++++++++++++++++------ 1 file changed, 47 insertions(+), 7 deletions(-) --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -1238,10 +1238,6 @@ local_irq_disable(); } -/* - * We need to flush the caches before going to sleep, lest we have - * dirty data in our caches when we come back up. - */ void __noreturn mwait_play_dead(unsigned int eax_hint) { struct mwait_cpu_dead *md = this_cpu_ptr(&mwait_cpu_dead); @@ -1288,6 +1284,50 @@ } /* + * We need to flush the caches before going to sleep, lest we have + * dirty data in our caches when we come back up. + */ +static inline void mwait_play_dead_cpuid_hint(void) +{ + unsigned int eax, ebx, ecx, edx; + unsigned int highest_cstate = 0; + unsigned int highest_subcstate = 0; + int i; + + if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD || + boot_cpu_data.x86_vendor == X86_VENDOR_HYGON) + return; + if (!this_cpu_has(X86_FEATURE_MWAIT)) + return; + if (!this_cpu_has(X86_FEATURE_CLFLUSH)) + return; + + eax = CPUID_LEAF_MWAIT; + ecx = 0; + native_cpuid(&eax, &ebx, &ecx, &edx); + + /* + * eax will be 0 if EDX enumeration is not valid. + * Initialized below to cstate, sub_cstate value when EDX is valid. + */ + if (!(ecx & CPUID5_ECX_EXTENSIONS_SUPPORTED)) { + eax = 0; + } else { + edx >>= MWAIT_SUBSTATE_SIZE; + for (i = 0; i < 7 && edx; i++, edx >>= MWAIT_SUBSTATE_SIZE) { + if (edx & MWAIT_SUBSTATE_MASK) { + highest_cstate = i; + highest_subcstate = edx & MWAIT_SUBSTATE_MASK; + } + } + eax = (highest_cstate << MWAIT_SUBSTATE_SIZE) | + (highest_subcstate - 1); + } + + mwait_play_dead(eax); +} + +/* * Kick all "offline" CPUs out of mwait on kexec(). See comment in * mwait_play_dead(). */ @@ -1337,9 +1377,9 @@ play_dead_common(); tboot_shutdown(TB_SHUTDOWN_WFS); - /* Below returns only on error. */ - cpuidle_play_dead(); - hlt_play_dead(); + mwait_play_dead_cpuid_hint(); + if (cpuidle_play_dead()) + hlt_play_dead(); } #else /* ... !CONFIG_HOTPLUG_CPU */ From patchwork Wed May 28 12:54:49 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Rafael J. Wysocki" X-Patchwork-Id: 893530 Received: from cloudserver094114.home.pl (cloudserver094114.home.pl [79.96.170.134]) (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 35A4228643A; Wed, 28 May 2025 13:59:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=79.96.170.134 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1748440790; cv=none; b=NAJJeQyJj3GQV2gS74A4bbJKV77RGDvXrhfoAvpSBn3pmdxJejsmi6obdVPrO3gcsJ07r3WmwQ5N7205H827nBhvfJjdhQezngaaHEWWJhfaRrOfzKVnB/ZPPlW8vdyxxo1sUUb0oOQZsl5OxiDhd5/Q8r4vIvGNniSadViIq34= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1748440790; c=relaxed/simple; bh=keU5ngDbfNyJ99ZyYcjp9U+daYH5n6t4r62lhQZewAM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=F9UnJvPxPqai2o3cztoPz2lCu5YflQE2Z66Lwb2KSLFh/fgbZRcZ+2Qkx43a9r1bsOyboUYJk6ke7TTsyznKd4MLRESqvnzfLm4U18Y3GX0/3RofaS4+3abb8zK0Kh2pZKfvQYBl97JbwaBpv9dY7S/GxWlRel+PqBqBiKZep7U= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=rjwysocki.net; spf=pass smtp.mailfrom=rjwysocki.net; dkim=pass (2048-bit key) header.d=rjwysocki.net header.i=@rjwysocki.net header.b=a9rwiP4Y; arc=none smtp.client-ip=79.96.170.134 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=rjwysocki.net Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=rjwysocki.net Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=rjwysocki.net header.i=@rjwysocki.net header.b="a9rwiP4Y" Received: from kreacher.localnet (unknown [5.63.189.50]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by cloudserver094114.home.pl (Postfix) with ESMTPSA id 96BD66680C5; Wed, 28 May 2025 14:55:01 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=rjwysocki.net; s=dkim; t=1748436902; bh=keU5ngDbfNyJ99ZyYcjp9U+daYH5n6t4r62lhQZewAM=; h=From:Subject:Date; b=a9rwiP4YBID5AEMl88r98X0/YUjecAMXTGehm+rI8XaSaDPHnfQct6wkChpjCUR2M 1YifvrF2Q3LcSuC5HIqDvTKY2DCp1IPDWJ5qoBN8hti6XCCZM1XTh+o3S4S1ET9/IL TnFFTfvJG5msYWh8BUHEuQZIJ26ZmqMcpvEqaiOXuQBcffT7b/S86RFFbmizl60+RO MnzYRJYcGRgpV/dnRppojDMibcZWpy3MvBp6JS/DRIcb/vPoVzvm52mu3jFBlFTFxe HhGxzUwUZfj1mSd8OCF1nxt42gFsIEWuKMY/4mitvxFnsm7wrDcvZyaUwRAzv4tg1b 9spZzrow5b17w== From: "Rafael J. Wysocki" To: x86 Maintainers Cc: LKML , Linux PM , Len Brown , Peter Zijlstra , Thomas Gleixner , Borislav Petkov , Dave Hansen , Artem Bityutskiy , "Gautham R. Shenoy" , Ingo Molnar , Todd Brandt Subject: [PATCH v1 2/2] x86/smp: Prefer cpuidle_play_dead() to mwait_play_dead_cpuid_hint() Date: Wed, 28 May 2025 14:54:49 +0200 Message-ID: <3633769.iIbC2pHGDl@rjwysocki.net> In-Reply-To: <2006806.PYKUYFuaPT@rjwysocki.net> References: <2006806.PYKUYFuaPT@rjwysocki.net> Precedence: bulk X-Mailing-List: linux-pm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-CLIENT-IP: 5.63.189.50 X-CLIENT-HOSTNAME: 5.63.189.50 X-VADE-SPAMSTATE: clean X-VADE-SPAMCAUSE: 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 X-DCC--Metrics: v370.home.net.pl 1024; Body=12 Fuz1=12 Fuz2=12 From: "Rafael J. Wysocki" Currently, mwait_play_dead_cpuid_hint() looks up the MWAIT hint of the deepest idle state by inspecting CPUID leaf 0x05 with the assumption that, if the number of sub-states for a given major C-state is nonzero, those sub-states are always represented by consecutive numbers starting from 0. This assumption is not based on the documented platform behavior and in fact it is not met on recent Intel platforms (eg. Sierra Forest). For this reason, it is better to let the cpuidle driver for the given platform put CPUs going offline into appropriate idle state and only if that fails, fall back to mwait_play_dead_cpuid_hint(), which may still be the next best "play dead" variant if cpuidle is not available. For example, when "nosmt" is passed to the kernel in the command line, SMT siblings are disabled early, before cpuidle gets ready, but they need to be put into sufficiently deep idle states to allow the whole processor to reach deep package idle states, like PC10, later on. Tested-by: Todd Brandt Signed-off-by: Rafael J. Wysocki --- arch/x86/kernel/smpboot.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -1377,9 +1377,10 @@ play_dead_common(); tboot_shutdown(TB_SHUTDOWN_WFS); + /* Each call in the following sequence returns only on errors. */ + cpuidle_play_dead(); mwait_play_dead_cpuid_hint(); - if (cpuidle_play_dead()) - hlt_play_dead(); + hlt_play_dead(); } #else /* ... !CONFIG_HOTPLUG_CPU */