From patchwork Thu Jun 22 00:36:01 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Waiman Long X-Patchwork-Id: 695175 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5C61FEB64DD for ; Thu, 22 Jun 2023 00:37:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229944AbjFVAhj (ORCPT ); Wed, 21 Jun 2023 20:37:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60394 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229921AbjFVAhf (ORCPT ); Wed, 21 Jun 2023 20:37:35 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0F3941738 for ; Wed, 21 Jun 2023 17:36:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1687394208; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Y2K8vEOPDcz7x2LNRwFb2B2QKeE2WWX5WNiQAkU03hs=; b=TLcEcLg7X5IShQBN1OjWI2RLJh7yb1khwGnIUNb+sseARKo/m91brSBehS1p/VQVeqg1Lq mfkJ+k9avTHSn7u96qHqCDrxB7RVmdWcxDJ7G6J0HRze/lRKZ5YxfeMd+JMFZLAlKlDDw0 NWDw8ft4F2kyl+S3AeslTXZxCh4WHj4= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-225-bkmuxB6oP4CXjIe5kkZ_qw-1; Wed, 21 Jun 2023 20:36:44 -0400 X-MC-Unique: bkmuxB6oP4CXjIe5kkZ_qw-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id BEC2D85A58A; Thu, 22 Jun 2023 00:36:42 +0000 (UTC) Received: from llong.com (unknown [10.22.33.143]) by smtp.corp.redhat.com (Postfix) with ESMTP id 09587112132E; Thu, 22 Jun 2023 00:36:41 +0000 (UTC) From: Waiman Long To: Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Josh Poimboeuf , Pawan Gupta , Jacob Pan , Len Brown Cc: linux-kernel@vger.kernel.org, x86@kernel.org, linux-pm@vger.kernel.org, Robin Jarry , Joe Mario , Waiman Long Subject: [PATCH v3 1/3] x86/idle: Disable IBRS when cpu is offline Date: Wed, 21 Jun 2023 20:36:01 -0400 Message-Id: <20230622003603.1188364-2-longman@redhat.com> In-Reply-To: <20230622003603.1188364-1-longman@redhat.com> References: <20230622003603.1188364-1-longman@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.3 Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org Commit bf5835bcdb96 ("intel_idle: Disable IBRS during long idle") disables IBRS when the CPU enters long idle. However, when a CPU becomes offline, the IBRS bit is still set when X86_FEATURE_KERNEL_IBRS is enabled. That will impact the performance of a sibling CPU. Mitigate this performance impact by clearing all the mitigation bits in SPEC_CTRL MSR when offline. When the CPU is online again, it will be re-initialized and so restoring the SPEC_CTRL value isn't needed. Add a comment to say that native_play_dead() is a __noreturn function, but it can't be marked as such to avoid confusion about the missing MSR restoration code. Signed-off-by: Waiman Long --- arch/x86/kernel/smpboot.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 352f0ce1ece4..7bc33885518c 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -84,6 +84,7 @@ #include #include #include +#include /* representing HT siblings of each logical CPU */ DEFINE_PER_CPU_READ_MOSTLY(cpumask_var_t, cpu_sibling_map); @@ -1836,8 +1837,17 @@ void __noreturn hlt_play_dead(void) } } +/* + * naitve_play_dead() is essentially a __noreturn function, but it can't + * be marked as such as the compiler may complain about it. + */ void native_play_dead(void) { + if (cpu_feature_enabled(X86_FEATURE_KERNEL_IBRS)) { + this_cpu_write(x86_spec_ctrl_current, 0); + native_wrmsrl(MSR_IA32_SPEC_CTRL, 0); + } + play_dead_common(); tboot_shutdown(TB_SHUTDOWN_WFS); From patchwork Thu Jun 22 00:36:02 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Waiman Long X-Patchwork-Id: 695600 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6B178EB64D8 for ; Thu, 22 Jun 2023 00:37:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229978AbjFVAhk (ORCPT ); Wed, 21 Jun 2023 20:37:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60392 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229915AbjFVAhf (ORCPT ); Wed, 21 Jun 2023 20:37:35 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D4FFA198E for ; Wed, 21 Jun 2023 17:36:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1687394208; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=ZnY7DyJzG9u4tj8u43HUsl2yxKZDOEzNFGoyTY9ZN9E=; b=JDLg7nKdQKg/0qSrLO2QEDbLWQGp4BimwcVoFEoMPfXVoaMx4FYSpelqQJkzTMaBCbm5pa hJgkh2NWpla+DGyVaTxFPCfzbJrPwBdjv2Nl7/i3GkPAxUfwC+Dp+zyd4WhR0m0JxanbgI Aib0xdpKIVBy5zHXaMrpwknFi8RBgYI= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-328-8lweGLeKPVGsRXDFNdxTew-1; Wed, 21 Jun 2023 20:36:44 -0400 X-MC-Unique: 8lweGLeKPVGsRXDFNdxTew-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 9663B805AF6; Thu, 22 Jun 2023 00:36:43 +0000 (UTC) Received: from llong.com (unknown [10.22.33.143]) by smtp.corp.redhat.com (Postfix) with ESMTP id D1D12112132C; Thu, 22 Jun 2023 00:36:42 +0000 (UTC) From: Waiman Long To: Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Josh Poimboeuf , Pawan Gupta , Jacob Pan , Len Brown Cc: linux-kernel@vger.kernel.org, x86@kernel.org, linux-pm@vger.kernel.org, Robin Jarry , Joe Mario , Waiman Long Subject: [PATCH v3 2/3] intel_idle: Sync up the SPEC_CTRL MSR value to x86_spec_ctrl_current Date: Wed, 21 Jun 2023 20:36:02 -0400 Message-Id: <20230622003603.1188364-3-longman@redhat.com> In-Reply-To: <20230622003603.1188364-1-longman@redhat.com> References: <20230622003603.1188364-1-longman@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.3 Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org When intel_idle_ibrs() is called, it modifies the SPEC_CTRL MSR to 0 in order disable IBRS. However, the new MSR value isn't reflected in x86_spec_ctrl_current which is at odd with the other code that keep track of its state in that percpu variable. Fix that by updating x86_spec_ctrl_current percpu value to always match the content of the SPEC_CTRL MSR. Signed-off-by: Waiman Long --- drivers/idle/intel_idle.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c index aa2d19db2b1d..07fa23707b3c 100644 --- a/drivers/idle/intel_idle.c +++ b/drivers/idle/intel_idle.c @@ -181,13 +181,17 @@ static __cpuidle int intel_idle_ibrs(struct cpuidle_device *dev, u64 spec_ctrl = spec_ctrl_current(); int ret; - if (smt_active) + if (smt_active) { + __this_cpu_write(x86_spec_ctrl_current, 0); native_wrmsrl(MSR_IA32_SPEC_CTRL, 0); + } ret = __intel_idle(dev, drv, index); - if (smt_active) + if (smt_active) { native_wrmsrl(MSR_IA32_SPEC_CTRL, spec_ctrl); + __this_cpu_write(x86_spec_ctrl_current, spec_ctrl); + } return ret; } From patchwork Thu Jun 22 00:36:03 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Waiman Long X-Patchwork-Id: 695176 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 28910EB64D7 for ; Thu, 22 Jun 2023 00:37:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229893AbjFVAh3 (ORCPT ); Wed, 21 Jun 2023 20:37:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60376 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229784AbjFVAh2 (ORCPT ); Wed, 21 Jun 2023 20:37:28 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 46EA51981 for ; Wed, 21 Jun 2023 17:36:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1687394206; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=1r3PzJd7BfuII/LkCpH6/mpfYzdtX6yj52D21WLcU08=; b=Fa6s3/82zSqlQLElrUZDKgzdIbL0dFU+80QxjfvagWhAVlce23NZt/GbILI4YRLNnSS3zN kcvC4EAivNnBa2rDwGIDInsixXQ6Dk9t9YHYyhvWKnfUOWk5s2FYqGtwlgT7MMef77rRtK +W94UeXvZL/rVGetD8UbPUlF/W4aGog= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-433-Wf_xTA3DNyOMMsljI4GqDw-1; Wed, 21 Jun 2023 20:36:45 -0400 X-MC-Unique: Wf_xTA3DNyOMMsljI4GqDw-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 66929800193; Thu, 22 Jun 2023 00:36:44 +0000 (UTC) Received: from llong.com (unknown [10.22.33.143]) by smtp.corp.redhat.com (Postfix) with ESMTP id A8FA8112132C; Thu, 22 Jun 2023 00:36:43 +0000 (UTC) From: Waiman Long To: Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Josh Poimboeuf , Pawan Gupta , Jacob Pan , Len Brown Cc: linux-kernel@vger.kernel.org, x86@kernel.org, linux-pm@vger.kernel.org, Robin Jarry , Joe Mario , Waiman Long Subject: [PATCH v3 3/3] intel_idle: Add ibrs_off module parameter to force disable IBRS Date: Wed, 21 Jun 2023 20:36:03 -0400 Message-Id: <20230622003603.1188364-4-longman@redhat.com> In-Reply-To: <20230622003603.1188364-1-longman@redhat.com> References: <20230622003603.1188364-1-longman@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.3 Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org Commit bf5835bcdb96 ("intel_idle: Disable IBRS during long idle") disables IBRS when the cstate is 6 or lower. However, there are some use cases where a customer may want to use max_cstate=1 to lower latency. Such use cases will suffer from the performance degradation caused by the enabling of IBRS in the sibling idle thread. Add a "ibrs_off" module parameter to force disable IBRS and the CPUIDLE_FLAG_IRQ_ENABLE flag if set. In the case of a Skylake server with max_cstate=1, this new ibrs_off option will likely increase the IRQ response latency as IRQ will now be disabled. When running SPECjbb2015 with cstates set to C1 on a Skylake system. First test when the kernel is booted with: "intel_idle.ibrs_off" max-jOPS = 117828, critical-jOPS = 66047 Then retest when the kernel is booted without the "intel_idle.ibrs_off" added. max-jOPS = 116408, critical-jOPS = 58958 That means booting with "intel_idle.ibrs_off" improves performance by: max-jOPS: 1.2%, which could be considered noise range. critical-jOPS: 12%, which is definitely a solid improvement. The admin-guide/pm/intel_idle.rst file is updated to add a description about the new "ibrs_off" module parameter. Signed-off-by: Waiman Long --- Documentation/admin-guide/pm/intel_idle.rst | 17 ++++++++++++++++- drivers/idle/intel_idle.c | 14 ++++++++++++-- 2 files changed, 28 insertions(+), 3 deletions(-) diff --git a/Documentation/admin-guide/pm/intel_idle.rst b/Documentation/admin-guide/pm/intel_idle.rst index b799a43da62e..8604e6d1fe2c 100644 --- a/Documentation/admin-guide/pm/intel_idle.rst +++ b/Documentation/admin-guide/pm/intel_idle.rst @@ -170,7 +170,7 @@ and ``idle=nomwait``. If any of them is present in the kernel command line, the ``MWAIT`` instruction is not allowed to be used, so the initialization of ``intel_idle`` will fail. -Apart from that there are four module parameters recognized by ``intel_idle`` +Apart from that there are five module parameters recognized by ``intel_idle`` itself that can be set via the kernel command line (they cannot be updated via sysfs, so that is the only way to change their values). @@ -216,6 +216,21 @@ are ignored). The idle states disabled this way can be enabled (on a per-CPU basis) from user space via ``sysfs``. +The ``ibrs_off`` module parameter is a boolean flag (default to false). It is +used to control if IBRS (Indirect Branch Restricted Speculation) should be +turned off, if set, when the CPU enters an idle state. This flag will not +affect CPUs that are using Enhanced IBRS which can remain on with little +performance impact. + +For some CPUs, IBRS will be selected as mitigation for Spectre v2 and Retbleed +security vulnerabilities by default. Leaving the IBRS mode on while idling may +have a performance impact on its sibling CPU. The IBRS mode will be turned off +by default when the CPU enters into a deep idle state, but not in some +shallower ones. Setting the ``ibrs_off`` module parameter will force the IBRS +mode to off when the CPU is in any one of the available idle states. This may +help performance of a sibling CPU at the expense of a slightly higher wakeup +latency for the idle CPU. + .. _intel-idle-core-and-package-idle-states: diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c index 07fa23707b3c..8bbf1e6d845c 100644 --- a/drivers/idle/intel_idle.c +++ b/drivers/idle/intel_idle.c @@ -69,6 +69,7 @@ static int max_cstate = CPUIDLE_STATE_MAX - 1; static unsigned int disabled_states_mask __read_mostly; static unsigned int preferred_states_mask __read_mostly; static bool force_irq_on __read_mostly; +static bool ibrs_off __read_mostly; static struct cpuidle_device __percpu *intel_idle_cpuidle_devices; @@ -1907,12 +1908,15 @@ static void __init intel_idle_init_cstates_icpu(struct cpuidle_driver *drv) WARN_ON_ONCE(state->flags & CPUIDLE_FLAG_IRQ_ENABLE); state->enter = intel_idle_xstate; } else if (cpu_feature_enabled(X86_FEATURE_KERNEL_IBRS) && - state->flags & CPUIDLE_FLAG_IBRS) { + ((state->flags & CPUIDLE_FLAG_IBRS) || ibrs_off)) { /* * IBRS mitigation requires that C-states are entered * with interrupts disabled. */ - WARN_ON_ONCE(state->flags & CPUIDLE_FLAG_IRQ_ENABLE); + if (ibrs_off && (state->flags & CPUIDLE_FLAG_IRQ_ENABLE)) + state->flags &= ~CPUIDLE_FLAG_IRQ_ENABLE; + else + WARN_ON_ONCE(state->flags & CPUIDLE_FLAG_IRQ_ENABLE); state->enter = intel_idle_ibrs; } else if (state->flags & CPUIDLE_FLAG_IRQ_ENABLE) { state->enter = intel_idle_irq; @@ -2165,3 +2169,9 @@ MODULE_PARM_DESC(preferred_cstates, "Mask of preferred idle states"); * 'CPUIDLE_FLAG_INIT_XSTATE' and 'CPUIDLE_FLAG_IBRS' flags. */ module_param(force_irq_on, bool, 0444); +/* + * Force the disabling of IBRS when X86_FEATURE_KERNEL_IBRS is on and + * CPUIDLE_FLAG_IRQ_ENABLE isn't set. + */ +module_param(ibrs_off, bool, 0444); +MODULE_PARM_DESC(ibrs_off, "Disable IBRS when idle");