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=-2.5 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 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 2206EC433E0 for ; Wed, 17 Jun 2020 11:25:58 +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 E6F14208B3 for ; Wed, 17 Jun 2020 11:25:57 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="WHWBQkck"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="jhvfeYbW" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E6F14208B3 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-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=/4TduPEDtEJiMEl70t+VFnKgnYJ/Rpt51yxmF6vVwkA=; b=WHWBQkcklt8Xl6 7CbvGSU43VF00oSGG5OnBAjRmPMVjw41wxheRwo4BT3iDkM+jeYMhy1qiGeVs9dvWZLXV7OtQ1kU0 mgjWh2gf95BjlqiphNXQgDjcgyUpV29euI5Yvpk8/aJrko6lh6ekf7XgNnMPF5shCdLT1MgyUhcuG 6mUD6U6moVubkD6czMkpo5XM8wfBPJatLEEpSZPnGTHzwLkq9w6gwdX0oDoE6cS6OSVj6YGBbVvFQ Kr7CNNkQPUn3aAEId+dr5+8rdu2HAGnFCsV0kpKXnZ7pb7Kyop9q8DoRWnBR2qviseWrr0oiW/Vwo ACe2vajsJcL7TicRAQMA==; 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 1jlWCU-00035P-3K; Wed, 17 Jun 2020 11:25:50 +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 1jlWCQ-00034v-SJ for linux-arm-kernel@lists.infradead.org; Wed, 17 Jun 2020 11:25:48 +0000 Received: from willie-the-truck (236.31.169.217.in-addr.arpa [217.169.31.236]) (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 DAC23208B3; Wed, 17 Jun 2020 11:25:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1592393146; bh=W594DViUjrIetKV1VqEvjPiBD/hTtwpui+EbbP9Kj1M=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=jhvfeYbWqVCQE27JPT//05UBtgQRxoihtA8d+SyuljO/pDs81WxU4S4CN95QxxSkm oTdJUVkk3BtDj0x6Hl4R2hV6tkTVSrZ3il0gokpHIZmrkJPlawNmbZ9Hj+Yzw8Bz/i 7XQu4LTEb/Hq0zUTNQzOI2Iiy7wVfcx1V0tVd1Ps= Date: Wed, 17 Jun 2020 12:25:42 +0100 From: Will Deacon To: Marc Zyngier Subject: Re: Query regarding ERRATUM_1418040 Message-ID: <20200617112542.GB3503@willie-the-truck> References: <1ce7dad5-a981-5968-cc34-7648faea8636@codeaurora.org> <062be27686369d28bd2054a54c307400@misterjones.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <062be27686369d28bd2054a54c307400@misterjones.org> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200617_042546_931898_44D6006F X-CRM114-Status: GOOD ( 14.45 ) 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: Neeraj Upadhyay , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Jun 17, 2020 at 12:19:16PM +0100, Marc Zyngier wrote: > On 2020-06-17 09:55, Neeraj Upadhyay wrote: > > 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. Hmm, but in conjunction with the previous point, doesn't this mean if some CPUs are affected by an erratum which requires CNTVCT trapping for AArch64 and others are affected by 1418040, then the former won't actually be trapped? Maybe we should preserve ARCH_TIMER_USR_VCT_ACCESS_EN for AArch64 tasks instead of setting it unconditionally? Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel