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Wysocki" Subject: [PATCH 1/4] x86: Add a comment about the "magic" behind shadow sti before mwait Date: Wed, 15 Nov 2023 10:13:22 -0500 Message-ID: <20231115151325.6262-2-frederic@kernel.org> X-Mailer: git-send-email 2.42.1 In-Reply-To: <20231115151325.6262-1-frederic@kernel.org> References: <20231115151325.6262-1-frederic@kernel.org> MIME-Version: 1.0 X-Spam-Status: No, score=-2.2 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF, RCVD_IN_DNSWL_BLOCKED,SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (snail.vger.email [0.0.0.0]); Wed, 15 Nov 2023 07:14:12 -0800 (PST) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1782643428227540222 X-GMAIL-MSGID: 1782643428227540222 Add a note to make sure we never miss and break the requirements behind it. Acked-by: Rafael J. Wysocki Signed-off-by: Frederic Weisbecker --- arch/x86/include/asm/mwait.h | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/arch/x86/include/asm/mwait.h b/arch/x86/include/asm/mwait.h index 778df05f8539..341ee4f1d91e 100644 --- a/arch/x86/include/asm/mwait.h +++ b/arch/x86/include/asm/mwait.h @@ -87,6 +87,15 @@ static __always_inline void __mwaitx(unsigned long eax, unsigned long ebx, :: "a" (eax), "b" (ebx), "c" (ecx)); } +/* + * Re-enable interrupts right upon calling mwait in such a way that + * no interrupt can fire _before_ the execution of mwait, ie: no + * instruction must be placed between "sti" and "mwait". + * + * This is necessary because if an interrupt queues a timer before + * executing mwait, it would otherwise go unnoticed and the next tick + * would not be reprogrammed accordingly before mwait ever wakes up. + */ static __always_inline void __sti_mwait(unsigned long eax, unsigned long ecx) { mds_idle_clear_cpu_buffers(); From patchwork Wed Nov 15 15:13:23 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Frederic Weisbecker X-Patchwork-Id: 165440 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a59:b909:0:b0:403:3b70:6f57 with SMTP id t9csp2605591vqg; Wed, 15 Nov 2023 07:14:42 -0800 (PST) X-Google-Smtp-Source: AGHT+IGrtFDQazFgJCzAHzQGt2t5r2lm8jS2YFNK87opzhwMqiLO3LYgBXda/zaUY745DZXaFi4K X-Received: by 2002:a05:6a20:8e23:b0:186:6b45:b75f with SMTP id y35-20020a056a208e2300b001866b45b75fmr10067477pzj.53.1700061282040; Wed, 15 Nov 2023 07:14:42 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1700061282; cv=none; d=google.com; s=arc-20160816; b=IaGiV1T0VQFl3X3b/SbEMKkjcFECZPbrvcv4uDPQl7SZV94gHY7wPMaKLegtBrAJhI c+AWqvdinFquL4OhrUS0354IAN5MZ4Voyi0pfvo+hA3nx6T8hHIV1e1svOBnruyq+UAW 42l/arExbj1wTS3r6/aQj3xbX7bK3E/TE1/sgfgE1/rM0NxGMkKlnoQZ0iLN2B6oqGJk TBEAl+zkH0w5s0mX5UFOUFjuRVQCyJGtBT3yav0h6f0IU8AFUxD2mc611XLede3UM8yx UpUq2eyvoZPIg88igRBfFKMII6WCP8ruoJpT21m6z4HbutR5BTwMIc5qVZC0IuBiOXW+ /+mw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:content-transfer-encoding:mime-version :references:in-reply-to:message-id:date:subject:cc:to:from :dkim-signature; bh=ciHALJuqd/QArjtSbPzwwJtSpK/poIF7pkyAnlkdyzM=; fh=Ivm/f9oPVddvYLeCK7X7FPY4HbbyM471g0wwB/hncPQ=; b=Xfm4M/FR0RKamMAaXAo/maaBX3v9GrecyPdCQ2P5IFbJZnFXMLDoE4JHPTVSeq4JXg ZTDcu6NINxhXFZjMm+Sif5V0tO1p9bYyM+CEUYwSivKTjHbk0xNRFr/OJWXyE9dXreW3 1r4v0IJd7/agB/n63lu/gS5bCnyzBGngeOj6uC6493E01xCW+6d5Zj+0F2CE9wPjqKtz QYLfmrAvHdIR2VEjFYf+Ji27KHS+rc0YXbVydM+M/IK6e/UA5DJOJANT3cFmZem0A5IP BV+dTgrC6rXzKqtFybYLk+EP9BH9XkKqyqTt82Z0pUmtXeddqIAFyXDUmQduWhg1Modw TObg== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@kernel.org header.s=k20201202 header.b=UqzQv9sF; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:5 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=kernel.org Received: from groat.vger.email (groat.vger.email. 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Wysocki" , Frederic Weisbecker Subject: [PATCH 2/4] x86: Fix CPUIDLE_FLAG_IRQ_ENABLE leaking timer reprogram Date: Wed, 15 Nov 2023 10:13:23 -0500 Message-ID: <20231115151325.6262-3-frederic@kernel.org> X-Mailer: git-send-email 2.42.1 In-Reply-To: <20231115151325.6262-1-frederic@kernel.org> References: <20231115151325.6262-1-frederic@kernel.org> MIME-Version: 1.0 X-Spam-Status: No, score=-1.3 required=5.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on groat.vger.email Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (groat.vger.email [0.0.0.0]); Wed, 15 Nov 2023 07:14:39 -0800 (PST) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1782643458685107972 X-GMAIL-MSGID: 1782643458685107972 From: Peter Zijlstra intel_idle_irq() re-enables IRQs very early. As a result, an interrupt may fire before mwait() is eventually called. If such an interrupt queues a timer, it may go unnoticed until mwait returns and the idle loop handles the tick re-evaluation. And monitoring TIF_NEED_RESCHED doesn't help because a local timer enqueue doesn't set that flag. The issue is mitigated by the fact that this idle handler is only invoked for shallow C-states when, presumably, the next tick is supposed to be close enough. There may still be rare cases though when the next tick is far away and the selected C-state is shallow, resulting in a timer getting ignored for a while. Fix this with using sti_mwait() whose IRQ-reenablement only triggers upon calling mwait(), dealing with the race while keeping the interrupt latency within acceptable bounds. Fixes: c227233ad64c (intel_idle: enable interrupts before C1 on Xeons) Not-yet-signed-off-by: Peter Zijlstra Acked-by: Rafael J. Wysocki Signed-off-by: Frederic Weisbecker --- arch/x86/include/asm/mwait.h | 11 +++++++++-- drivers/idle/intel_idle.c | 19 +++++++------------ 2 files changed, 16 insertions(+), 14 deletions(-) diff --git a/arch/x86/include/asm/mwait.h b/arch/x86/include/asm/mwait.h index 341ee4f1d91e..920426d691ce 100644 --- a/arch/x86/include/asm/mwait.h +++ b/arch/x86/include/asm/mwait.h @@ -124,8 +124,15 @@ static __always_inline void mwait_idle_with_hints(unsigned long eax, unsigned lo } __monitor((void *)¤t_thread_info()->flags, 0, 0); - if (!need_resched()) - __mwait(eax, ecx); + + if (!need_resched()) { + if (ecx & 1) { + __mwait(eax, ecx); + } else { + __sti_mwait(eax, ecx); + raw_local_irq_disable(); + } + } } current_clr_polling(); } diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c index dcda0afecfc5..3e01a6b23e75 100644 --- a/drivers/idle/intel_idle.c +++ b/drivers/idle/intel_idle.c @@ -131,11 +131,12 @@ static unsigned int mwait_substates __initdata; #define MWAIT2flg(eax) ((eax & 0xFF) << 24) static __always_inline int __intel_idle(struct cpuidle_device *dev, - struct cpuidle_driver *drv, int index) + struct cpuidle_driver *drv, + int index, bool irqoff) { struct cpuidle_state *state = &drv->states[index]; unsigned long eax = flg2MWAIT(state->flags); - unsigned long ecx = 1; /* break on interrupt flag */ + unsigned long ecx = 1*irqoff; /* break on interrupt flag */ mwait_idle_with_hints(eax, ecx); @@ -159,19 +160,13 @@ static __always_inline int __intel_idle(struct cpuidle_device *dev, static __cpuidle int intel_idle(struct cpuidle_device *dev, struct cpuidle_driver *drv, int index) { - return __intel_idle(dev, drv, index); + return __intel_idle(dev, drv, index, true); } static __cpuidle int intel_idle_irq(struct cpuidle_device *dev, struct cpuidle_driver *drv, int index) { - int ret; - - raw_local_irq_enable(); - ret = __intel_idle(dev, drv, index); - raw_local_irq_disable(); - - return ret; + return __intel_idle(dev, drv, index, false); } static __cpuidle int intel_idle_ibrs(struct cpuidle_device *dev, @@ -184,7 +179,7 @@ static __cpuidle int intel_idle_ibrs(struct cpuidle_device *dev, if (smt_active) __update_spec_ctrl(0); - ret = __intel_idle(dev, drv, index); + ret = __intel_idle(dev, drv, index, true); if (smt_active) __update_spec_ctrl(spec_ctrl); @@ -196,7 +191,7 @@ static __cpuidle int intel_idle_xstate(struct cpuidle_device *dev, struct cpuidle_driver *drv, int index) { fpu_idle_fpregs(); - return __intel_idle(dev, drv, index); + return __intel_idle(dev, drv, index, true); } /** From patchwork Wed Nov 15 15:13:24 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Frederic Weisbecker X-Patchwork-Id: 165441 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a59:b909:0:b0:403:3b70:6f57 with SMTP id t9csp2605678vqg; Wed, 15 Nov 2023 07:14:50 -0800 (PST) X-Google-Smtp-Source: AGHT+IFNDd9yTMEIdM7EP3F5yxcm9JcakooV9dUsO2igxa4A4J4jOTveTeZ82svGfk+L57IMY6gx X-Received: by 2002:a05:6a20:244b:b0:14d:6309:fc96 with SMTP id t11-20020a056a20244b00b0014d6309fc96mr11471789pzc.4.1700061290264; Wed, 15 Nov 2023 07:14:50 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1700061290; cv=none; d=google.com; s=arc-20160816; b=hbg5ge0fc531URByjsEGJEiJdSZ2QRMG+sYMYoskHO2nNfmx8m0lA1dzGQha8q+d98 E+hkoGmV5kBtKgbtWfDg/68t5oyUb6BPnOX1HXTMGer317r9brHgwW2m3aJYjvi00bDL qeKh5tczp8xcZDRBYf585MpmWzm0t2AFwgenBC8Wo96E1MjQkmfVO7NayhBPQeQj/6lB 8Auk8y1f82Ls7PqdLpkLmcC00G/+rJ26jKZFz5ZhyCyRzkRtlEUtMcKiF0HN+77Lsiic 2RKXPMvne0z7gqiXm9u01zBrVJzcHIpGlyoDWfX+cuWQZEKl7gpMyxD75T8d/Osf9Qhx e/oQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:content-transfer-encoding:mime-version :references:in-reply-to:message-id:date:subject:cc:to:from :dkim-signature; bh=gXBM4+jjqNI6ShI3pMwXdx9ihI+g+PeOrL8L79kGSJU=; fh=vOxJ5zAh/ByOGHIIhVBN1rQVKUP9RG+2PkGMcshoCBs=; b=cMlo94j9Gq2g/7sezzYjuxO5ZK7RNuzKdvbGd24lANGumNc4cX9zzO7RmuJVZwA2R3 lrMErcwH8LA2EbNDSlvw6fAa9zvvdXsAmMM6dq1BtvY1qcECJPNG4iGQd42cALVNYeSI G988LA4M37AuIAutIhimhEKS+TAJLbgYOxgo77Lx6/uWrcOJCV3SsNFFsMyqtp29lGOh LyUUfZoiLHKuZIirxsFRCXh1bCkOLrEG4xFBbIP4BYi0uuvcXOEwGCglXvNVUQ7cbULi KZmochrZtnhHBaRGccb++ZR77W8uj6713oOFAH6QIMDq5LXJL1r2VxOnrkOdBTnrb9vp WLwA== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@kernel.org header.s=k20201202 header.b=bLxROmPD; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.38 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=kernel.org Received: from fry.vger.email (fry.vger.email. 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Wysocki" Subject: [PATCH 3/4] x86: Remove __current_clr_polling() from mwait_idle() Date: Wed, 15 Nov 2023 10:13:24 -0500 Message-ID: <20231115151325.6262-4-frederic@kernel.org> X-Mailer: git-send-email 2.42.1 In-Reply-To: <20231115151325.6262-1-frederic@kernel.org> References: <20231115151325.6262-1-frederic@kernel.org> MIME-Version: 1.0 X-Spam-Status: No, score=-1.3 required=5.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on fry.vger.email Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (fry.vger.email [0.0.0.0]); Wed, 15 Nov 2023 07:14:47 -0800 (PST) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1782643467497276358 X-GMAIL-MSGID: 1782643467497276358 mwait_idle() is only ever called through by cpuidle, either from default_idle_call() or from cpuidle_enter(). In any case cpuidle_idle_call() sets again TIF_NR_POLLING after calling it so there is no point for this atomic operation upon idle exit. Acked-by: Rafael J. Wysocki Signed-off-by: Frederic Weisbecker --- arch/x86/kernel/process.c | 1 - 1 file changed, 1 deletion(-) diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index b6f4e8399fca..fc7a38084606 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -930,7 +930,6 @@ static __cpuidle void mwait_idle(void) raw_local_irq_disable(); } } - __current_clr_polling(); } void select_idle_routine(const struct cpuinfo_x86 *c) From patchwork Wed Nov 15 15:13:25 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Frederic Weisbecker X-Patchwork-Id: 165439 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a59:b909:0:b0:403:3b70:6f57 with SMTP id t9csp2605353vqg; Wed, 15 Nov 2023 07:14:25 -0800 (PST) X-Google-Smtp-Source: AGHT+IH+sLp65riFA0t987lWGgAkmCgxbp0WttZeZmxePoQgiNPLiktuMtfIaTZFaLmjLgbFHVtP X-Received: by 2002:a05:6a21:6d96:b0:186:4430:5d16 with SMTP id wl22-20020a056a216d9600b0018644305d16mr13641357pzb.61.1700061265142; Wed, 15 Nov 2023 07:14:25 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1700061265; cv=none; d=google.com; s=arc-20160816; b=fyTmiccQ6St8B1Q3E+ItLV8eOOALK+EsfsJUH0JjqqY1V+fHBc2koYzX+BsXUPC1Rw uUcffSzAGYbvZE7b9hx0kmLXuYMNPdvopcrONc4AaQ9RuTuGeqpHm3GyuT9Wl0PbeNrL r9Bq35hbZpkG3tnQDZm9kMfLFjPJRSMo4nmif9ECKfho4FGwsVYRr+xGOMxPjZ5lKxZ0 bQQKN7yMqqiGnGCGs+u+8WSk8WOBD9tKP1HDtnK5uzAnunZyhOkrMcR4Mj021lU1NfXQ iiUBckc2Ud2aekL/ecxzamqVWqyUUb399blDpUAihsi61GHNOsefQlcv8HPNZaV2biCT bugg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:content-transfer-encoding:mime-version :references:in-reply-to:message-id:date:subject:cc:to:from :dkim-signature; bh=6D0IcbnKu38KXda50Tk8L29X61iI2OOdAtrKLf2f1Mo=; fh=vOxJ5zAh/ByOGHIIhVBN1rQVKUP9RG+2PkGMcshoCBs=; b=FuuEn5cbhG9zM4xnqh8tSsrd/6YdTPQVOsLwFTy25kZpBC675UaFoZ98w/Wy9fQtSr j11h+l1I15Z7ND16QyAyJGoQiZTqqmyScyr0nQE+gVjgFUSJE6kHy4CyHfFwjh1vRwlf V+LgMqU+uHfB8P2YrVoI90FIt9qnpsowtqzA3VSdQhky01AZFDwVji7x61VpokmPc+zA Rlr/WCGlsVcNoVhE4gotwrnliJ1v83xzTQ6Cw3jA7duK1Z1UnJY0kWgiKwo87GrxW1aS CFUftonYzt4XBTOw235ermvGeQ7IM7pGJin5xZ5JffldChyotGGAA7cS45qlZH6uYthb 8zjQ== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@kernel.org header.s=k20201202 header.b=s5m+7PM5; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.37 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=kernel.org Received: from snail.vger.email (snail.vger.email. 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Wysocki" Subject: [PATCH 4/4] x86: Remove the current_clr_polling() call upon mwait exit Date: Wed, 15 Nov 2023 10:13:25 -0500 Message-ID: <20231115151325.6262-5-frederic@kernel.org> X-Mailer: git-send-email 2.42.1 In-Reply-To: <20231115151325.6262-1-frederic@kernel.org> References: <20231115151325.6262-1-frederic@kernel.org> MIME-Version: 1.0 X-Spam-Status: No, score=-2.2 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF, RCVD_IN_DNSWL_BLOCKED,SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (snail.vger.email [0.0.0.0]); Wed, 15 Nov 2023 07:14:23 -0800 (PST) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1782643441213348323 X-GMAIL-MSGID: 1782643441213348323 mwait_idle_with_hints() is mostly called from cpuidle which already sets back TIF_NR_POLLING and fold TIF_NEED_RESCHED if necessary. The only non-cpuidle caller is power_saving_thread() which acts as an idle loop and is the only reason why mwait_idle_with_hints() carries a costly fully ordered atomic operation upon idle exit. Make this overhead proper to power_saving_thread() instead which already duplicates quite some cpuidle code. Acked-by: Rafael J. Wysocki Signed-off-by: Frederic Weisbecker --- arch/x86/include/asm/mwait.h | 1 - drivers/acpi/acpi_pad.c | 1 + 2 files changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/include/asm/mwait.h b/arch/x86/include/asm/mwait.h index 920426d691ce..c1be3775b94a 100644 --- a/arch/x86/include/asm/mwait.h +++ b/arch/x86/include/asm/mwait.h @@ -134,7 +134,6 @@ static __always_inline void mwait_idle_with_hints(unsigned long eax, unsigned lo } } } - current_clr_polling(); } /* diff --git a/drivers/acpi/acpi_pad.c b/drivers/acpi/acpi_pad.c index bd1ad07f0290..86b57123713f 100644 --- a/drivers/acpi/acpi_pad.c +++ b/drivers/acpi/acpi_pad.c @@ -175,6 +175,7 @@ static int power_saving_thread(void *data) stop_critical_timings(); mwait_idle_with_hints(power_saving_mwait_eax, 1); + current_clr_polling(); start_critical_timings(); tick_broadcast_exit();