From patchwork Tue Jun 20 14:06:22 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Waiman Long X-Patchwork-Id: 13285957 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 ACA8EEB64DB for ; Tue, 20 Jun 2023 14:10:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233056AbjFTOJw (ORCPT ); Tue, 20 Jun 2023 10:09:52 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59286 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233179AbjFTOJq (ORCPT ); Tue, 20 Jun 2023 10:09:46 -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 31F5EE60 for ; Tue, 20 Jun 2023 07:08:58 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1687270137; 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=+DkmE6hETltBu3bPa+S3gxCm/8V55tvpJfZg0jQ8Gvw=; b=RbrYDQodAoRTDl7yNfYx9xXnJVfCT8r5+HNJ88d801pVpe+zgwgApyDUuStl3SiViQQSYc 4PBdGmJHsIgvTQVrYuNlnxSU1J1of2FPYSYntJ74j3vy8RhQPcD4RI8HHjgUAor5ORBi82 j9et0ziX2lL1fc9IuASSYKk73JpewSY= 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-37-2A_wpEtmMHKKyXq6jJXqlg-1; Tue, 20 Jun 2023 10:08:34 -0400 X-MC-Unique: 2A_wpEtmMHKKyXq6jJXqlg-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 5130888711B; Tue, 20 Jun 2023 14:06:33 +0000 (UTC) Received: from llong.com (unknown [10.22.34.46]) by smtp.corp.redhat.com (Postfix) with ESMTP id 91537425356; Tue, 20 Jun 2023 14:06:32 +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 2/5] x86/idle: Disable IBRS when cpu is offline Date: Tue, 20 Jun 2023 10:06:22 -0400 Message-Id: <20230620140625.1001886-3-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 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 and restoring the value of the MSR when it becomes online again. Signed-off-by: Waiman Long --- arch/x86/kernel/smpboot.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 352f0ce1ece4..5ff82fef413c 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); @@ -1838,12 +1839,24 @@ void __noreturn hlt_play_dead(void) void native_play_dead(void) { + u64 spec_ctrl = spec_ctrl_current(); + + 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); mwait_play_dead(); if (cpuidle_play_dead()) hlt_play_dead(); + + if (cpu_feature_enabled(X86_FEATURE_KERNEL_IBRS)) { + native_wrmsrl(MSR_IA32_SPEC_CTRL, spec_ctrl); + this_cpu_write(x86_spec_ctrl_current, spec_ctrl); + } } #else /* ... !CONFIG_HOTPLUG_CPU */