From patchwork Tue Jun 20 14:06:24 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Waiman Long X-Patchwork-Id: 694671 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 2DFF7EB64D7 for ; Tue, 20 Jun 2023 14:10:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232144AbjFTOJx (ORCPT ); Tue, 20 Jun 2023 10:09:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59320 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233205AbjFTOJt (ORCPT ); Tue, 20 Jun 2023 10:09:49 -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 20880E68 for ; Tue, 20 Jun 2023 07:09:08 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1687270147; 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=+LliIS9GzKVY7r+2Pd1dAZaFc5KbOmlOofBoCL5VmAU=; b=Uxrnv2+DdKsm5B12CJO9YlS2w5bgKV/Y/gMvEi2fOzenDCdrUIC+/OaGfnVdXfgBI4pvEE S8S3QmU5LrQJx70Qu6rB5QuBC4jHzK1b7rrV7rB7K6IDKlXI4COvRYiTWsdxHIk7iW/rdY QiAZzzvyH39sZt5UJk8hRxiJ63+o/O4= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-9-uWgs1p_OOFmaIFWneI7weA-1; Tue, 20 Jun 2023 10:08:56 -0400 X-MC-Unique: uWgs1p_OOFmaIFWneI7weA-1 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.rdu2.redhat.com [10.11.54.10]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id EC30F28EA71F; Tue, 20 Jun 2023 14:06:34 +0000 (UTC) Received: from llong.com (unknown [10.22.34.46]) by smtp.corp.redhat.com (Postfix) with ESMTP id 2A712425356; Tue, 20 Jun 2023 14:06:34 +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 v2 4/5] intel_idle: Add no_ibrs module parameter to force disable IBRS Date: Tue, 20 Jun 2023 10:06:24 -0400 Message-Id: <20230620140625.1001886-5-longman@redhat.com> In-Reply-To: <20230620140625.1001886-1-longman@redhat.com> References: <20230620140625.1001886-1-longman@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.10 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 "no_ibrs" 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 no_ibrs option will increase the IRQ response latency as IRQ will now be disabled. Signed-off-by: Waiman Long --- drivers/idle/intel_idle.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c index 07fa23707b3c..366dacccc971 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 no_ibrs __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) || no_ibrs)) { /* * IBRS mitigation requires that C-states are entered * with interrupts disabled. */ - WARN_ON_ONCE(state->flags & CPUIDLE_FLAG_IRQ_ENABLE); + if (no_ibrs && (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(no_ibrs, bool, 0444); +MODULE_PARM_DESC(no_ibrs, "Disable IBRS when idle");