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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 977DBC433EF for ; Wed, 8 Dec 2021 16:26:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232691AbhLHQ3z (ORCPT ); Wed, 8 Dec 2021 11:29:55 -0500 Received: from mail-oi1-f178.google.com ([209.85.167.178]:39635 "EHLO mail-oi1-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232478AbhLHQ3z (ORCPT ); Wed, 8 Dec 2021 11:29:55 -0500 Received: by mail-oi1-f178.google.com with SMTP id bf8so4792500oib.6; Wed, 08 Dec 2021 08:26:23 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=2QlMufJTFNT9Vlv4+AjFEwWUWEtafIKRof1v70zz+CQ=; b=zi0yp4MpYrYKTuLziNNrXxwj5OYTHR48Nxo4N9q9g4zDgwrhdrIqIFucjOlPSrBiPH tTSXosVebp3zraHBtelvB1/JFNglmO6S1sA4d0tZ56oONd5BfupByqUchoRXzYdYEa0n MHatpkfA9n00tMJcLVXvOCHYzKcFPRMeYXGJG8+rGelA6/9HlGmkv7BtvU9N5AskVWE5 twMTkxqBOxRhmC0FsZrtYykAwjjjjt3F9Rxqoxc3EKnSyPrnEXamiqrJ7QgdxH6vLD1L tafQAuOyOwwbNH4311fzcltLUnrrBsNGKQ13m5UMAcnGYeSe+rrGblqYGi5y6uymTKT7 D+Qw== X-Gm-Message-State: AOAM530SO0SeY+4ejl41UwSuQyKXU8IAdHqOhTq/L04ZECPwYNQQnTUy l3+ilyatWLn/w7fYVRDjIwl7B2IZbiPvenycSTk= X-Google-Smtp-Source: ABdhPJxJ3fAV2TWfgdNnVCyB2a7/UMGSRKzTH2CjKdQVUDpC8XZGb/+27um+mGrUKok9PraxdxDiW+Bd1hsbgLUSOA4= X-Received: by 2002:a05:6808:1454:: with SMTP id x20mr409139oiv.166.1638980783303; Wed, 08 Dec 2021 08:26:23 -0800 (PST) MIME-Version: 1.0 References: <20211206122952.74139-1-kirill.shutemov@linux.intel.com> <20211206122952.74139-4-kirill.shutemov@linux.intel.com> In-Reply-To: From: "Rafael J. Wysocki" Date: Wed, 8 Dec 2021 17:26:12 +0100 Message-ID: Subject: Re: [PATCH 3/4] ACPI: processor idle: Only flush cache on entering C3 To: Peter Zijlstra Cc: "Kirill A. Shutemov" , "Rafael J. Wysocki" , Andi Kleen , Borislav Petkov , Dan Williams , Dave Hansen , "H. Peter Anvin" , Kuppuswamy Sathyanarayanan , ACPI Devel Maling List , Linux Kernel Mailing List , Ingo Molnar , "Rafael J. Wysocki" , Kuppuswamy Sathyanarayanan , Thomas Gleixner , Tony Luck , "the arch/x86 maintainers" Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org On Mon, Dec 6, 2021 at 4:03 PM Peter Zijlstra wrote: > > On Mon, Dec 06, 2021 at 03:29:51PM +0300, Kirill A. Shutemov wrote: > > According to the ACPI spec v6.4, section 8.2, cache flushing required > > on entering C3 power state. > > > > Avoid flushing cache on entering other power states. > > > > Signed-off-by: Kirill A. Shutemov > > --- > > drivers/acpi/processor_idle.c | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c > > index 76ef1bcc8848..01495aca850e 100644 > > --- a/drivers/acpi/processor_idle.c > > +++ b/drivers/acpi/processor_idle.c > > @@ -567,7 +567,8 @@ static int acpi_idle_play_dead(struct cpuidle_device *dev, int index) > > { > > struct acpi_processor_cx *cx = per_cpu(acpi_cstate[index], dev->cpu); > > > > - ACPI_FLUSH_CPU_CACHE(); > > + if (cx->type == ACPI_STATE_C3) > > + ACPI_FLUSH_CPU_CACHE(); > > > > acpi_idle_enter() already does this, acpi_idle_enter_s2idle() has it > confused again, No, they do the same thing: acpi_idle_enter_bm() if flags.bm_check is set. > Also, I think acpi_idle_enter() does it too late; consider > acpi_idle_enter_mb(). Either that or the BM crud needs more comments. I think the latter. Evidently, acpi_idle_play_dead(() doesn't support FFH and the BM thing, so it is only necessary to flush the cache when using ACPI_CSTATE_SYSTEMIO and when cx->type is C3.