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=-5.0 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no 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 1C9D0C433E0 for ; Thu, 4 Feb 2021 10:49:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CD46A64D92 for ; Thu, 4 Feb 2021 10:49:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235435AbhBDKsr (ORCPT ); Thu, 4 Feb 2021 05:48:47 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34998 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234873AbhBDKsn (ORCPT ); Thu, 4 Feb 2021 05:48:43 -0500 Received: from pandora.armlinux.org.uk (pandora.armlinux.org.uk [IPv6:2001:4d48:ad52:32c8:5054:ff:fe00:142]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9566FC061573 for ; Thu, 4 Feb 2021 02:48:03 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=armlinux.org.uk; s=pandora-2019; h=Sender:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=BXeiae7l+uiV2zg/Ou/pjTEevpYTR1/eunOFBBITs+I=; b=bliQkgzFwbBNiLrEIJtiW4P+E Th/uUs2Y7zrd9TEHVqjOsPUGb/k1wMRdbSWLdU7kwaXd8xfTc4TZKg7UmaoGXd1mWBR9JiINhu2ND A9MY2WFWQiZ5KntkbN74fZyqOkdi182h0hxNwQgWiptmgaj6mntyEervSg6Io7IZZMC3J/Uw89BCz nWENbbk1XtW4J9KDZUU+YsuMoH03UfDiKiAwSdyV/oM85rv2vzT0khXhgePZI/ElITVwuDYpxy71N lCbzibEZ1gCIu7y9K9GmStKLzBGSai2Jd6HAM3189Z2tVOngwLp54Qm350+f/KpBt7rUMoCl4BaD4 rD5N59+iA==; Received: from shell.armlinux.org.uk ([fd8f:7570:feb6:1:5054:ff:fe00:4ec]:39048) by pandora.armlinux.org.uk with esmtpsa (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1l7cB8-0006SM-2m; Thu, 04 Feb 2021 10:48:02 +0000 Received: from linux by shell.armlinux.org.uk with local (Exim 4.92) (envelope-from ) id 1l7cAN-000564-1Y; Thu, 04 Feb 2021 10:47:15 +0000 Date: Thu, 4 Feb 2021 10:47:15 +0000 From: Russell King - ARM Linux admin To: Ard Biesheuvel Cc: Guillaume Tucker , Geert Uytterhoeven , Linux Kernel Mailing List , Linus Walleij , Linux ARM , Nicolas Pitre , "kernelci-results@groups.io" Subject: Re: next/master bisection: baseline.login on rk3288-rock2-square Message-ID: <20210204104714.GU1463@shell.armlinux.org.uk> References: <601b773a.1c69fb81.9f381.a32a@mx.google.com> <6c65bcef-d4e7-25fa-43cf-2c435bb61bb9@collabora.com> <20210204100601.GT1463@shell.armlinux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: Russell King - ARM Linux admin Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 04, 2021 at 11:27:16AM +0100, Ard Biesheuvel wrote: > Hi Russell, > > If Guillaume is willing to do the experiment, and it fixes the issue, > it proves that rk3288 is relying on the flush before the MMU is > disabled, and so in that case, the fix is trivial, and we can just > apply it. > > If the experiment fails (which would mean rk3288 does not tolerate the > cache maintenance being performed after cache off), it is going to be > hairy, and so it will definitely take more time. > > So in the latter case (or if Guillaume does not get back to us), I > think reverting my queued fix is the only sane option. But in that > case, may I suggest that we queue the revert of the original by-VA > change for v5.12 so it gets lots of coverage in -next, and allows us > an opportunity to come up with a proper fix in the same timeframe, and > backport the revert and the subsequent fix as a pair? Otherwise, we'll > end up in the situation where v5.10.x until today has by-va, v5.10.x-y > has set/way, and v5.10y+ has by-va again. (I don't think we care about > anything before that, given that v5.4 predates any of this) I'm suggesting dropping your fix (9052/1) and reverting "ARM: decompressor: switch to by-VA cache maintenance for v7 cores" which gets us to a point where _both_ regressions are fixed. I'm of the opinion that the by-VA patch was incorrect when it was merged (it caused a regression), and it's only a performance improvement. Our attempts so far to fix it are just causing other regressions. So, I think it is reasonable to revert both back to a known good point which has worked over a decade. If doing so causes regressions (which I think is unlikely), then that would be unfortunate but alas is a price that's worth paying to get back to a known good point - since then we're not stacking regression fixes on top of other regression fixes. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!