From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B1F77C00307 for ; Mon, 9 Sep 2019 07:39:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8C3C421D71 for ; Mon, 9 Sep 2019 07:39:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388213AbfIIHjk (ORCPT ); Mon, 9 Sep 2019 03:39:40 -0400 Received: from mga17.intel.com ([192.55.52.151]:2203 "EHLO mga17.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726026AbfIIHjk (ORCPT ); Mon, 9 Sep 2019 03:39:40 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga002.jf.intel.com ([10.7.209.21]) by fmsmga107.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 09 Sep 2019 00:39:40 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.64,484,1559545200"; d="scan'208";a="196113218" Received: from fyin-dev.sh.intel.com ([10.239.143.122]) by orsmga002.jf.intel.com with ESMTP; 09 Sep 2019 00:39:38 -0700 From: Yin Fengwei Cc: "Rafael J. Wysocki" , Len Brown , linux-acpi@vger.kernel.org (open list:ACPI), linux-kernel@vger.kernel.org (open list) Subject: [RESEND] ACPI / processor_idle: use dead loop instead of io port access for wait Date: Mon, 9 Sep 2019 15:39:37 +0800 Message-Id: <20190909073937.31554-1-fengwei.yin@intel.com> X-Mailer: git-send-email 2.19.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit To: unlisted-recipients:; (no To-header on input) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In function acpi_idle_do_entry(), we do an io port access to guarantee hardware behavior. But it could trigger unnecessary vmexit for virtualization environemnt. >From the comments of this part of code, we could use busy wait instead of io port access to guarantee hardware behavior and avoid unnecessary vmexit. Signed-off-by: Yin Fengwei --- drivers/acpi/processor_idle.c | 33 ++++++++++++++++++++++++++++++--- 1 file changed, 30 insertions(+), 3 deletions(-) diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c index ed56c6d20b08..676553228e8f 100644 --- a/drivers/acpi/processor_idle.c +++ b/drivers/acpi/processor_idle.c @@ -55,6 +55,8 @@ struct cpuidle_driver acpi_idle_driver = { }; #ifdef CONFIG_ACPI_PROCESSOR_CSTATE +static struct timespec64 dummy_delta = {0L, 0L}; + static DEFINE_PER_CPU(struct acpi_processor_cx * [CPUIDLE_STATE_MAX], acpi_cstate); @@ -64,6 +66,18 @@ static int disabled_by_idle_boot_param(void) boot_option_idle_override == IDLE_HALT; } +static void dummy_wait(void) +{ + struct timespec64 now, target; + + ktime_get_real_ts64(&now); + target = timespec64_add(now, dummy_delta); + + do { + ktime_get_real_ts64(&now); + } while (timespec64_compare(&now, &target) < 0); +} + /* * IBM ThinkPad R40e crashes mysteriously when going into C2 or C3. * For now disable this. Probably a bug somewhere else. @@ -660,8 +674,12 @@ static void __cpuidle acpi_idle_do_entry(struct acpi_processor_cx *cx) inb(cx->address); /* Dummy wait op - must do something useless after P_LVL2 read because chipsets cannot guarantee that STPCLK# signal - gets asserted in time to freeze execution properly. */ - inl(acpi_gbl_FADT.xpm_timer_block.address); + gets asserted in time to freeze execution properly. + + Previously, we do io port access here which could trigger + unnecessary trap to HV for virtualization env. We use dead + loop here to avoid the impact to virtualization env. */ + dummy_wait(); } } @@ -683,7 +701,7 @@ static int acpi_idle_play_dead(struct cpuidle_device *dev, int index) else if (cx->entry_method == ACPI_CSTATE_SYSTEMIO) { inb(cx->address); /* See comment in acpi_idle_do_entry() */ - inl(acpi_gbl_FADT.xpm_timer_block.address); + dummy_wait(); } else return -ENODEV; } @@ -902,6 +920,7 @@ static inline void acpi_processor_cstate_first_run_checks(void) { acpi_status status; static int first_run; + struct timespec64 ts0, ts1; if (first_run) return; @@ -912,6 +931,13 @@ static inline void acpi_processor_cstate_first_run_checks(void) max_cstate); first_run++; + /* profiling the time used for dummy wait op */ + ktime_get_real_ts64(&ts0); + inl(acpi_gbl_FADT.xpm_timer_block.address); + ktime_get_real_ts64(&ts1); + + dummy_delta = timespec64_sub(ts1, ts0); + if (acpi_gbl_FADT.cst_control && !nocst) { status = acpi_os_write_port(acpi_gbl_FADT.smi_command, acpi_gbl_FADT.cst_control, 8); @@ -920,6 +946,7 @@ static inline void acpi_processor_cstate_first_run_checks(void) "Notifying BIOS of _CST ability failed")); } } + #else static inline int disabled_by_idle_boot_param(void) { return 0; } -- 2.19.1