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=-1.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 E5E8EC433E0 for ; Wed, 17 Jun 2020 11:19:26 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id B62CD214DB for ; Wed, 17 Jun 2020 11:19:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="q9VF2Yq8"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="1MKZoIx8" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B62CD214DB Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender:Content-Type: Content-Transfer-Encoding:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:Message-ID:References:In-Reply-To:Subject:To:From: Date:MIME-Version:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=E3vfZRFp8ON01x4G0G+l3dINcIcuFAp9RsVkza2GJaQ=; b=q9VF2Yq8AmBxJo9mMmD2X63XS KWD16oo3MyfBeMWa/tbqqniyEighKtE1ekTKY586RH4mO5hl9SKRZ9PC5s1vy+tivO8lqlQpf/zlC gtcNaychPl+NyYvxRNJlc60euHwggkUgojYLAE9jo21/Pf5eOcyMAEyZMUK0r+hn6FsIROn+TM9KV 0hdUVlsb2qU0ccR39I8pTO5qYcjfA5wORuBiwnex3fs5A5YPdSD8EjOVfVQmemrFWZAE5X+Wbr+R1 bF1MjFKNqIgJaUUVURtHTrxBJ+bQ8YUtvEbjLE9rgtH7O+tt4Idf4fgKR8gWPoBxXv5e5ypjQcNNk MzKnC6FXw==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jlW6D-0005hp-8u; Wed, 17 Jun 2020 11:19:21 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jlW6A-0005hH-Vq for linux-arm-kernel@lists.infradead.org; Wed, 17 Jun 2020 11:19:20 +0000 Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 374B820734; Wed, 17 Jun 2020 11:19:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1592392758; bh=0vlsaIbPCoSgisoap8p2ZMimxwVUprfB/3q0TGaMWMk=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=1MKZoIx8WHOzkygBkUrQiNNssLoxt1Xar4dqJBstwPmejkOM3KHOXNz3N9OXmxzr/ HqCVkKORSZGFiZ7ZFh4rZyXRWe7OD+XO+YZ4uWilHOXBQ8l1uY1f8jumD+KkiKGAu5 MjJKdD1GhB6EJZhO0MRQ6ugMxNnw1yW1j40p5UGc= Received: from disco-boy.misterjones.org ([51.254.78.96] helo=www.loen.fr) by disco-boy.misterjones.org with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.92) (envelope-from ) id 1jlW68-003lXZ-LG; Wed, 17 Jun 2020 12:19:16 +0100 MIME-Version: 1.0 Date: Wed, 17 Jun 2020 12:19:16 +0100 From: Marc Zyngier To: Neeraj Upadhyay Subject: Re: Query regarding ERRATUM_1418040 In-Reply-To: <1ce7dad5-a981-5968-cc34-7648faea8636@codeaurora.org> References: <1ce7dad5-a981-5968-cc34-7648faea8636@codeaurora.org> User-Agent: Roundcube Webmail/1.4.5 Message-ID: <062be27686369d28bd2054a54c307400@misterjones.org> X-Sender: maz@kernel.org X-SA-Exim-Connect-IP: 51.254.78.96 X-SA-Exim-Rcpt-To: neeraju@codeaurora.org, will@kernel.org, linux-arm-kernel@lists.infradead.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200617_041919_040961_09C65BBD X-CRM114-Status: GOOD ( 10.28 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: will@kernel.org, linux-arm-kernel@lists.infradead.org Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org [Thanks Will for pointing me to this email] Hi Neeraj, In the future, please use my kernel.org address, as I no longer work for ARM. On 2020-06-17 09:55, Neeraj Upadhyay wrote: > Hi, > > I have query regarding the errata 1418040 [1]. Here, on kernel exit to > EL0 64 bit mode, will it always enable ARCH_TIMER_USR_VCT_ACCESS_EN; > and override any other erratas, which might require EL0 direct vct > access to be disabled for 64 bit also? So far, I am not aware of any erratum that would require traps of CNTVCT_EL0 to EL1 when running AArch64 userspace for CPUs that are affected by ARM-1418040. If such an erratum exists, it would have to be handled separately. > Also, this errata applies > mitigation for all CPUs (on return to 32 bit EL0), even if, not all > cpus are impacted by the errata? Indeed. There isn't much we can do to avoid it here, unless you want to read some per-CPU variable that tells you whether the CPU is affected. This would add to the cost of the mitigation , and isn't an appealing prospect. Thanks, M. -- Jazz is not dead. It just smells funny... _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel