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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 59360C0218D for ; Fri, 31 Jan 2025 11:03:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=YojF4QfnKMR3dDmrpuJUH9Oc76V6pfYrEerAmaRhlJo=; b=jtSlOO2k5biwd3idb9PhLjFj9X 1xDh/1ZRlKTNhH9auyQkja4jjQs4TwDdBkEwnWjWFt2ZNK9plKEL3nQqbd9/AN+uw6cOeuRa1fzaP SxA7bOh07uh4kK2pn99gjK8jJFWnMAUP265WrvC1SFgLlbcCcjN1NSIfSN5loIePmDtqxHjswDCW0 Os8cJYamHe0iFaHSCwtpdYrjxil9HKUREsjLaeKB2yas5HN9tEoutwHAFhcyPF5Azt6I2x1EQEhSW toQMHblOLrnKiBuhMZkoFln/gCFwYGVMYCXo2xChJ8OBRyI5X+rWMRrgvWJGTunr2GAQ8De4/pkB3 k70uSh0Q==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tdonh-0000000ASFa-2eB5; Fri, 31 Jan 2025 11:03:05 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tdomN-0000000ASB9-2Aep for linux-arm-kernel@lists.infradead.org; Fri, 31 Jan 2025 11:01:44 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 3C83E497; Fri, 31 Jan 2025 03:02:08 -0800 (PST) Received: from J2N7QTR9R3 (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 24B813F63F; Fri, 31 Jan 2025 03:01:41 -0800 (PST) Date: Fri, 31 Jan 2025 11:01:38 +0000 From: Mark Rutland To: Oliver Upton Cc: linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com, joey.gouly@arm.com, kvmarm@lists.linux.dev, maz@kernel.org, suzuki.poulose@arm.com, will@kernel.org, yuzenghui@huawei.com Subject: Re: [PATCH 0/4] arm64: mitigate CVE-2024-7881 in the absence of firmware mitigation Message-ID: References: <20250128155428.210645-1-mark.rutland@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250131_030143_603131_B0797A84 X-CRM114-Status: GOOD ( 23.18 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Jan 30, 2025 at 01:48:53PM -0800, Oliver Upton wrote: > Hi Mark, > > On Tue, Jan 28, 2025 at 03:54:24PM +0000, Mark Rutland wrote: > > On some CPUs from Arm Ltd, it is possible for unprivileged code to cause > > a hardware prefetcher to form an address using the contents of a memory > > location which is accessible by privileged accesses in the active > > translation regime, potentially leaking the contents of this memory > > location via a side channel. This has been assigned CVE-2024-7881: > > > > https://developer.arm.com/Arm%20Security%20Center/Arm%20CPU%20Vulnerability%20CVE-2024-7881 > > > > Arm's recommended mitigation is that firmware configures an > > IMPLEMENTATION DEFINED control bit (CPUACTLR6_EL1[41]) to disable the > > affected prefetcher, and updates to Trusted Firmware-A are available to > > do this. For systems which have not yet recevied a firmware update, KPTI > > can help to mitigate the issue. > > > > These patches enable KPTI for affected parts when the firmware > > mitigation is not present. The presence of the mitigation is identified > > by the presence of the SMCCC_ARCH_WORKAROUND_4 SMCCC call, which was > > deployed with the mitigation. This is documented in the SMCCC 1.6 G BET0 > > specification: > > > > https://developer.arm.com/documentation/den0028/gbet0/?lang=en > > > > I have tested this on a few configurations of virtual platforms. I'd > > appreciate any feedback, especially on the KVM changes. > > The KVM changes look reasonable and follow the usual model for this > crud. It would be nice to report the mitigation state to userspace > somehow as I would like to have a KVM selftest for all of the hardware > vulnerabilities. Lemme go figure that out. Just to check, do you mean exposed through a KVM mechanism, or under /sys/devices/system/cpu/vulnerabilities/ ? I assume the latter. > But anyway, > > Reviewed-by: Oliver Upton Thanks; much appreciated! Mark.