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 17CAACDB46E for ; Thu, 12 Oct 2023 14:53:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378990AbjJLOxA (ORCPT ); Thu, 12 Oct 2023 10:53:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59530 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231290AbjJLOw5 (ORCPT ); Thu, 12 Oct 2023 10:52:57 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A59B4C0 for ; Thu, 12 Oct 2023 07:52:55 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id BDC7CC433C7; Thu, 12 Oct 2023 14:52:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1697122375; bh=IYDm8ofYKOZAFbxQa32MHYpNBNA79HhiV1G9gyxN4IQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=JVnBLfyrM0aoLkeHm29EX0fPCHIKaXsix+jYVpXjcHwoD7xcD0ZAM4ePIeH3yU/nD 7yTfYPhRsbMS1Z3U2ReHBjOxva0twYJOmkJ/Tl6SjS3UbEmLX0VZznvXCE1E7FYoce L5F/CHl8HjKMXjx0V/xYH23HX3iR6Xg4RN928MsGT6hzzWnszfyJ1Qqv4RdtP8/A6Z r4KKIp/Ouw7+MS75BHr8TGm6NhdiW96up4OgOQhbZ84qzAsGjaLLs4VJZQQ4TU6EEW B+4CVRtgTCiBDpgvzM7Abf8cjcNXUQRF+0x+NkdYmUAa+IrcfkiBPg7GahJs80WXmp hTjR0Ulm1rJ1A== Date: Thu, 12 Oct 2023 22:40:46 +0800 From: Jisheng Zhang To: Conor Dooley Cc: Paul Walmsley , Palmer Dabbelt , Albert Ou , Guo Ren , linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 0/2] riscv: errata: thead: use riscv_nonstd_cache_ops for CMO Message-ID: References: <20231012141456.4078-1-jszhang@kernel.org> <20231012-remindful-coke-f9cfe950425f@spud> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20231012-remindful-coke-f9cfe950425f@spud> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 12, 2023 at 03:36:28PM +0100, Conor Dooley wrote: > On Thu, Oct 12, 2023 at 10:21:08PM +0800, Jisheng Zhang wrote: > > On Thu, Oct 12, 2023 at 10:14:54PM +0800, Jisheng Zhang wrote: > > > Previously, we use alternative mechanism to dynamically patch > > > the CMO operations for THEAD C906/C910 during boot for performance > > > reason. But as pointed out by Arnd, "there is already a significant > > > cost in accessing the invalidated cache lines afterwards, which is > > > likely going to be much higher than the cost of an indirect branch". > > > And indeed, there's no performance difference with GMAC and EMMC per > > > my test on Sipeed Lichee Pi 4A board. > > > > > > Use riscv_nonstd_cache_ops for THEAD C906/C910 CMO to simplify > > > the alternative code, and to acchieve Arnd's goal -- "I think > > > moving the THEAD ops at the same level as all nonstandard operations > > > makes sense, but I'd still leave CMO as an explicit fast path that > > > avoids the indirect branch. This seems like the right thing to do both > > > for readability and for platforms on which the indirect branch has a > > > noticeable overhead." > > > > > > To make bisect easy, I use two patches here: patch1 does the conversion > > > which just mimics current CMO behavior via. riscv_nonstd_cache_ops, I > > > assume no functionalities changes. patch2 uses T-HEAD PA based CMO > > > instructions so that we don't need to covert PA to VA. > > > > > > Hi Guo, > > > > > > I didn't use wback_inv for wback as you suggested during v1 reviewing, > > > this can be left as future optimizations. > > > > > > Thanks > > > > > > since v2: > > > - collect Reviewed-by tag > > > > Oh, I missed the tag collection, but I know maintainers are using b4 which can > > collect and apply tags automatically ;). let me know if want a new > > version. > > It doesn't collect tags (AFAIU) from earlier revisions though. oops I didn't know this before, just sent out v4 with real tag collection to make the merging progress smooth.