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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id D03F6C04A94 for ; Fri, 11 Aug 2023 15:32:21 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 52B236B0072; Fri, 11 Aug 2023 11:32:21 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 4DAD46B0074; Fri, 11 Aug 2023 11:32:21 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 3A3326B0078; Fri, 11 Aug 2023 11:32:21 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 297166B0072 for ; Fri, 11 Aug 2023 11:32:21 -0400 (EDT) Received: from smtpin29.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id D665AB2D1C for ; Fri, 11 Aug 2023 15:32:20 +0000 (UTC) X-FDA: 81112215240.29.3FB36A9 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by imf13.hostedemail.com (Postfix) with ESMTP id 33D3920036 for ; Fri, 11 Aug 2023 15:32:18 +0000 (UTC) Authentication-Results: imf13.hostedemail.com; dkim=none; dmarc=fail reason="SPF not aligned (relaxed), No valid DKIM" header.from=arm.com (policy=none); spf=pass (imf13.hostedemail.com: domain of cmarinas@kernel.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=cmarinas@kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1691767939; a=rsa-sha256; cv=none; b=RYYAyM7DwxQ63R6HvCPkDB5IXSwNLlBqBPEK8LlCkSnKTBXqs2Y0YShRjWFpq/8Hba2sMx 4GaWfnkIU4lYGDwzBrRrCnWnwQo3L1lz4gTzaKNKI6od2bORA3bewPzr+GMJlpTpNRY0DJ yyt8jzWXiZONELrEhout28Z1quHxk/w= ARC-Authentication-Results: i=1; imf13.hostedemail.com; dkim=none; dmarc=fail reason="SPF not aligned (relaxed), No valid DKIM" header.from=arm.com (policy=none); spf=pass (imf13.hostedemail.com: domain of cmarinas@kernel.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=cmarinas@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1691767939; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=mU7Lf/wd21vYQGZyDzQa8r+12bsg7sPJSfouVa5nHyE=; b=2X++jNNJUZ/3wyYfimAhIlZ/Z3gYg6NSVPwX7G9ME0ifRiiMCjcuY3j/8GSj9ieC2onyfn ZbmLg1rVZI12BUWuqXGUupNQCwu900rC19mjECydb4FGDRlEgkZhMVpTjGc4LS4O2b437s qcJ71SaCEUhVyUyQRgIF3iceiMTUIX8= 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 2102E61044; 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-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 33D3920036 X-Stat-Signature: uat9tdq7j38gpao9h6u1ckpsk5d5hpa4 X-Rspam-User: X-HE-Tag: 1691767938-554233 X-HE-Meta: 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 P8pw7O4q kpnrzre6qiQzxGP5BxWLpf80AtsOY+srzYB/kxwpHreQ+pKKx8XiYQAHsHu1hVN7P4ItTZhA/aPHNsvz4IGR77lM+srrihTli6BoCnE/WKEvJ7gTXYDB2aXlAkeE1FtJC7quYulnt9kS6mInxLL+cAQt0glEhTsQlOL6mTGEIt2dU/KwVyqxOBInu/KS0vk+/u46q/o6KBF9Wk7DpUMYvMIdb2qBeooPZrwMM6RkY+kAOMkOJhGFc5ikl24OJkd5V0Jkgqck/b8cV7ifrZHQW5WTk4lFY3eA3FfxO2hmVsxIGJShC/QqXowFsFnvQfeMrDHoUUc6wsIwroiuzvg3pXyqao5hP/qJvmdH437R/20n2EQKwn5lpVQ2D0XwjNn/s8Tt0DeqnG0h+EiIpQYj96a+sS/UKxav2Ie1rIvU0Bw+ZGumnQt/P1g4M1EGbUMosTB8Sb9EKF0g1+22F/1gFW0A2/i9FLrabu67YhUq45HWhnZo= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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