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 5894FC433FE for ; Thu, 7 Apr 2022 18:51:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1347006AbiDGSxB convert rfc822-to-8bit (ORCPT ); Thu, 7 Apr 2022 14:53:01 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54102 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1347003AbiDGSw4 (ORCPT ); Thu, 7 Apr 2022 14:52:56 -0400 Received: from gloria.sntech.de (gloria.sntech.de [185.11.138.130]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A79646A02E for ; Thu, 7 Apr 2022 11:50:53 -0700 (PDT) Received: from ip5b412258.dynamic.kabel-deutschland.de ([91.65.34.88] helo=diego.localnet) by gloria.sntech.de with esmtpsa (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1ncXDQ-0007Iv-1o; Thu, 07 Apr 2022 20:50:44 +0200 From: Heiko =?ISO-8859-1?Q?St=FCbner?= To: Christoph Hellwig Cc: Christoph Hellwig , palmer@dabbelt.com, paul.walmsley@sifive.com, aou@eecs.berkeley.edu, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, wefu@redhat.com, liush@allwinnertech.com, guoren@kernel.org, atishp@atishpatra.org, anup@brainfault.org, drew@beagleboard.org, arnd@arndb.de, wens@csie.org, maxime@cerno.tech, gfavor@ventanamicro.com, andrea.mondelli@huawei.com, behrensj@mit.edu, xinhaoqu@huawei.com, mick@ics.forth.gr, allen.baum@esperantotech.com, jscheid@ventanamicro.com, rtrauben@gmail.com, samuel@sholland.org, cmuellner@linux.com, philipp.tomsich@vrull.eu, Atish Patra Subject: Re: [PATCH v8 01/14] riscv: prevent null-pointer dereference with sbi_remote_fence_i Date: Thu, 07 Apr 2022 20:50:42 +0200 Message-ID: <2627651.mvXUDI8C0e@diego> In-Reply-To: <20220331123322.GA26378@lst.de> References: <20220324000710.575331-1-heiko@sntech.de> <2260961.n0HT0TaD9V@diego> <20220331123322.GA26378@lst.de> MIME-Version: 1.0 Content-Transfer-Encoding: 8BIT Content-Type: text/plain; charset="iso-8859-1" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am Donnerstag, 31. März 2022, 14:33:22 CEST schrieb Christoph Hellwig: > On Thu, Mar 31, 2022 at 02:28:06PM +0200, Heiko Stübner wrote: > > so essentially flushes the _local_ icache first and then tries to flush > > caches on other cores, either via an ipi or via sbi. > > > > The remote-fence callback is set correctly during sbi_init(). > > The other cores are only brought up after sbi-init is done. > > > > So it's not really about error reporting but making sure that flush_icache_all() > > does something sane even when still running on the first core. > > As I assume the "all" means on all available cores (which would be the > > core the system booted on). > > > > Does this make it clearer what this tries to solve? > > A little. Whatever code calls this early still seems broken to me > and just just do a local flush, though. Looking at this again made me realize that we don't need this patch anymore at all. In a previous revision the "main" alternatives apply-point was earlier, triggering the issue when the generic patching-functions wanted to flush the cache, but with the alternatives getting applied where they are now, the issue is not triggered anymore. And the "early" alternatives use a local flush anyway.