Received: by 2002:a05:7412:6592:b0:d7:7d3a:4fe2 with SMTP id m18csp1072765rdg; Fri, 11 Aug 2023 08:54:09 -0700 (PDT) X-Google-Smtp-Source: AGHT+IEGO9ZW3gBitAQBJixPMPcFqQzMXgO8aYCMblG6ixTtIwiK5AXk98ROdpptpusQT/AwZqgf X-Received: by 2002:aa7:88cd:0:b0:687:6184:deed with SMTP id k13-20020aa788cd000000b006876184deedmr2123271pff.22.1691769249040; Fri, 11 Aug 2023 08:54:09 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1691769249; cv=none; d=google.com; s=arc-20160816; b=d4yMjGnNPhAS3yIFAnWiBC6ObiV4MIU7hy8FL480crrwSo62/bcgIAksz0Yx68MaOf c2r6F1rg7YZSk3AEXwWwfmcMg9iPB/MYTNe6nojToco9jGQu28tQEGTLeA/2qubIDTql lsXkKmeJIMUVdFjarl1EZ25kiMoDNLmywrbgmmh6zNHLy5o3MDfhsfl/V8Ms3SZUnXSe ShSkWhHTmgKh3T2/qrw6s60ba9ADen4QvLxI7bI5Ibb/2moLp/9Jf9o5daQEaLNvYwaU Jbl8znpPpGrKeQwEmKN3Zrj0890Ok+oFPp6OPeJldOoWeVo+YTR8wOaTt3xJjEYJvpKL WjDA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:in-reply-to:content-disposition:mime-version :references:message-id:subject:cc:to:from:date; bh=mU7Lf/wd21vYQGZyDzQa8r+12bsg7sPJSfouVa5nHyE=; fh=2wxoOguWzzWu+YGUlY4iG2KZkVCU8hdxOZfl5CjkbsQ=; b=uaMgG7FQhlOG9diAHN8Px9Y8otch1N6czki67C7Bl+A+MufmWQGaFJhTh/BPVN02BR C2iqEAla5ZINIJ11zO7RIDq0aJ74XhrWaY2gKws92MifSXK8mlSFzSXZV6W4o/LP2HS8 YhduIwLU8Tr1BQGeRrfCnTJssDnKb1MGcR56rYipH0KrqwWZ4n8CDqdG3b7Iy67yaWnD uR8g33c46LVng9NZiVq3zHfJXrtPRsnOXf01n2lPvl7B0FkWms75wwRng6IYMkXKZFKF L5VNy1+twDEnISMQkkB35KAD4D1FZcH/bBo5bbGShzDIflfGHh6Tujb5ZIMOtbF223r1 MYdQ== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=arm.com Return-Path: Received: from out1.vger.email (out1.vger.email. [2620:137:e000::1:20]) by mx.google.com with ESMTP id k6-20020a654646000000b0056419b1dc17si3670580pgr.885.2023.08.11.08.53.57; Fri, 11 Aug 2023 08:54:09 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=arm.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236540AbjHKPcU (ORCPT + 99 others); Fri, 11 Aug 2023 11:32:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55534 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236500AbjHKPcT (ORCPT ); Fri, 11 Aug 2023 11:32:19 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8DC9319A5; Fri, 11 Aug 2023 08:32:18 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 214DE65E9D; Fri, 11 Aug 2023 15:32:18 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id AD3E1C433C7; Fri, 11 Aug 2023 15:32:12 +0000 (UTC) Date: Fri, 11 Aug 2023 16:32:10 +0100 From: Catalin Marinas To: Mark Brown Cc: Will Deacon , Jonathan Corbet , Andrew Morton , Marc Zyngier , Oliver Upton , James Morse , Suzuki K Poulose , Arnd Bergmann , Oleg Nesterov , Eric Biederman , Kees Cook , Shuah Khan , "Rick P. Edgecombe" , Deepak Gupta , Ard Biesheuvel , Szabolcs Nagy , "H.J. Lu" , Paul Walmsley , Palmer Dabbelt , Albert Ou , linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, kvmarm@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org Subject: Re: [PATCH v4 18/36] arm64/gcs: Context switch GCS state for EL0 Message-ID: References: <20230807-arm64-gcs-v4-0-68cfa37f9069@kernel.org> <20230807-arm64-gcs-v4-18-68cfa37f9069@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230807-arm64-gcs-v4-18-68cfa37f9069@kernel.org> X-Spam-Status: No, score=-1.6 required=5.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,RCVD_IN_DNSWL_BLOCKED,SPF_HELO_NONE, SPF_PASS autolearn=no autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Aug 07, 2023 at 11:00:23PM +0100, Mark Brown wrote: > @@ -271,12 +272,31 @@ static void flush_tagged_addr_state(void) > clear_thread_flag(TIF_TAGGED_ADDR); > } > > +#ifdef CONFIG_ARM64_GCS > + > +static void flush_gcs(void) > +{ > + if (system_supports_gcs()) { Nitpick: use "if (system_supports_gcs()) return" when we have more than a line in the conditional block (slightly more consistent with other places). > + gcs_free(current); > + current->thread.gcs_el0_mode = 0; > + write_sysreg_s(0, SYS_GCSCRE0_EL1); > + write_sysreg_s(0, SYS_GCSPR_EL0); > + } > +} Do we need and isb() or there's one on this path? If it's only EL0 making use of this register, we should be fine with the ERET before returning to user. Not sure whether the kernel uses this, GCSSTTR doesn't need it. > +static void gcs_thread_switch(struct task_struct *next) > +{ > + if (!system_supports_gcs()) > + return; > + > + gcs_preserve_current_state(); > + > + /* > + * Ensure that GCS changes are observable by/from other PEs in > + * case of migration. > + */ > + if (task_gcs_el0_enabled(current) || task_gcs_el0_enabled(next)) > + gcsb_dsync(); What's this barrier for? The spec (at least the version I have) only talks about accesses, nothing to do with the registers that we context switch here. -- Catalin