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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 0AA5ECA9EB9 for ; Thu, 24 Oct 2019 01:22:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D38A32086D for ; Thu, 24 Oct 2019 01:22:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389913AbfJXBWW (ORCPT ); Wed, 23 Oct 2019 21:22:22 -0400 Received: from mga03.intel.com ([134.134.136.65]:42223 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726925AbfJXBWV (ORCPT ); Wed, 23 Oct 2019 21:22:21 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by orsmga103.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 23 Oct 2019 18:22:21 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.68,222,1569308400"; d="scan'208";a="228325727" Received: from fyin-dev.sh.intel.com (HELO [10.239.143.122]) ([10.239.143.122]) by fmsmga002.fm.intel.com with ESMTP; 23 Oct 2019 18:22:19 -0700 Subject: Re: [PATCH v3] ACPI/processor_idle: Remove dummy wait if kernel is in guest mode To: David Laight , "linux-kernel@vger.kernel.org" , "linux-acpi@vger.kernel.org" , "rjw@rjwysocki.net" , "lenb@kernel.org" References: <20191023074945.17016-1-fengwei.yin@intel.com> <30ee0a348f624698801691f65eeecd87@AcuMS.aculab.com> From: Yin Fengwei Message-ID: <9bb3baef-b23e-a383-d50f-f795033c0c02@intel.com> Date: Thu, 24 Oct 2019 09:22:18 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <30ee0a348f624698801691f65eeecd87@AcuMS.aculab.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-acpi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org On 2019/10/23 下午4:45, David Laight wrote: > From: Yin Fengwei >> Sent: 23 October 2019 08:50 > > >> In function acpi_idle_do_entry(), an ioport access is used for dummy >> wait to guarantee hardware behavior. But it could trigger unnecessary >> vmexit if kernel is running as guest in virtualization environtment. >> >> If it's in virtualization environment, the deeper C state enter >> operation (inb()) will trap to hyervisor. It's not needed to do >> dummy wait after the inb() call. So we remove the dummy io port >> access to avoid unnecessary VMexit. >> >> We keep dummy io port access to maintain timing for native environment. >> >> Signed-off-by: Yin Fengwei >> --- >> ChangeLog: >> v2 -> v3: >> - Remove dummy io port access totally for virtualization env. >> >> v1 -> v2: >> - Use ndelay instead of dead loop for dummy delay. >> >> drivers/acpi/processor_idle.c | 36 ++++++++++++++++++++++++++++++++--- >> 1 file changed, 33 insertions(+), 3 deletions(-) >> >> diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c >> index ed56c6d20b08..0c4a97dd6917 100644 >> --- a/drivers/acpi/processor_idle.c >> +++ b/drivers/acpi/processor_idle.c >> @@ -58,6 +58,17 @@ struct cpuidle_driver acpi_idle_driver = { >> static >> DEFINE_PER_CPU(struct acpi_processor_cx * [CPUIDLE_STATE_MAX], acpi_cstate); >> >> +static void (*dummy_wait)(u64 address); >> + >> +static void default_dummy_wait(u64 address) >> +{ >> + inl(address); >> +} >> + >> +static void default_noop_wait(u64 address) >> +{ >> +} >> + > > Overengineered... > Just add: > > static void wait_for_freeze(void) > { > #ifdef CONFIG_X86 > /* No delay is needed if we are a guest */ > if (boot_cpu_has(X86_FEATURE_HYPERVISOR)) > return; > #endif > /* 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); > } > > and use it to replace the inl(). OK. I was trying to avoid any impact to native case. > > ... >> +#ifdef CONFIG_X86 >> + /* For x86, if we are running in guest, we don't need extra >> + * access ioport as dummy wait. >> + */ >> + if (boot_cpu_has(X86_FEATURE_HYPERVISOR)) { >> + pr_err("We are in virtual env"); >> + dummy_wait = default_noop_wait; >> + } else { >> + pr_err("We are not in virtual env"); >> + } >> +#endif > > WTF are the pr_err() for??? Sorry. Didn't remove my debug code... Regards Yin, Fengwei > > David > > - > Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK > Registration No: 1397386 (Wales) >