From nobody Fri Apr 4 21:25:15 2025 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=pass(p=none dis=none) header.from=redhat.com ARC-Seal: i=1; a=rsa-sha256; t=1739810330; cv=none; d=zohomail.com; s=zohoarc; b=Y1zfoYnVMTE1RY4JJGmokLs1xVb3cp5iCgi2poRc2gu3THGMygLqqip6b2VHdpwn0H8WyvqdlmJdGEddvnw4PbfcgKr1HgKUCoQIDOcdgEOLtzCGqanC2gwfH5S7ZQUkzvfBmfXCecf9SgTFTqnLwQM5hMcrCKtnS6iSbJdwu/E= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1739810330; h=Content-Type:Content-Transfer-Encoding:Cc:Cc:Date:Date:From:From:In-Reply-To:List-Subscribe:List-Post:List-Id:List-Archive:List-Help:List-Unsubscribe:MIME-Version:Message-ID:References:Sender:Subject:Subject:To:To:Message-Id:Reply-To; bh=v3Ka5DD552tfRB8O8dTkD7Lnt3ngyuMwpr7Jbz6905c=; b=RWpTHz1rLH59YbaQ++ZKlsKMYAX221Lv8NpJ6gT3Cnc4H1NjuH3itDjniepdTxPYuU9eha6Dpte2AKZP9Cv6ZUfouOQXBMG3e6BwqZAjMBgND/p8OWWs858MjzmIjnwCJRnAPa2iBvcvGVxhyfrCVX7DAwLVQmI2lmCH/3giS0Y= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=pass header.from= (p=none dis=none) Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 173981033081322.590398898129592; Mon, 17 Feb 2025 08:38:50 -0800 (PST) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1tk48Z-0000bs-8G; Mon, 17 Feb 2025 11:38:27 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1tk48X-0000Xl-58 for qemu-devel@nongnu.org; Mon, 17 Feb 2025 11:38:25 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1tk48U-0007G9-O5 for qemu-devel@nongnu.org; Mon, 17 Feb 2025 11:38:24 -0500 Received: from mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-489-mGn3oMIpPp6L2x004nL3jA-1; Mon, 17 Feb 2025 11:38:18 -0500 Received: from mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.40]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 5176D18EB2C3; Mon, 17 Feb 2025 16:38:14 +0000 (UTC) Received: from gezellig.redhat.com (unknown [10.44.32.23]) by mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 24DFD19560AA; Mon, 17 Feb 2025 16:38:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1739810302; h=from:from: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:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=v3Ka5DD552tfRB8O8dTkD7Lnt3ngyuMwpr7Jbz6905c=; b=ZrhR1e/v7eHpFQHLfem5JKyrX+mhQ/cnA11S53lhxDFFPriTaBjsvf4t+yPW9EKQiinfht nAE94epGTcSj4UgzYlA/tdimzDWXtkrjvvwDJOBHaFBZcTHcaSRd9NcTtzgaCH3pZqnxxH OC5FNe1q0+T7Y+8Pl9Fmt3GcdkSP3gc= X-MC-Unique: mGn3oMIpPp6L2x004nL3jA-1 X-Mimecast-MFC-AGG-ID: mGn3oMIpPp6L2x004nL3jA_1739810296 From: Kashyap Chamarthy To: qemu-devel@nongnu.org Cc: Ninad Palsule , sebott@redhat.com, maz@kernel.org, Andrew Jeffery , Alistair Francis , "Edgar E. Iglesias" , Tyrone Ting , Hao Wu , Zhenzhong Duan , =?UTF-8?q?Alex=20Benn=C3=A9e?= , Peter Maydell , =?UTF-8?q?C=C3=A9dric=20Le=20Goater?= , Steven Lee , Troy Lee , Joel Stanley , Eric Auger , Jamin Lin , Yi Liu , qemu-arm@nongnu.org, Alexandre Iooss , Kashyap Chamarthy Subject: [PATCH v2 2/3] docs/cpu-features: Update "PAuth" (Pointer Authentication) details Date: Mon, 17 Feb 2025 22:07:28 +0530 Message-ID: <20250217163732.3718617-3-kchamart@redhat.com> In-Reply-To: <20250217163732.3718617-1-kchamart@redhat.com> References: <20250217163732.3718617-1-kchamart@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.0 on 10.30.177.40 Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=170.10.129.124; envelope-from=kchamart@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, PP_MIME_FAKE_ASCII_TEXT=0.24, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1739810334340019100 Content-Type: text/plain; charset="utf-8" PAuth (Pointer Authentication), a security feature in software, is relevant for both KVM and QEMU. Relect this fact into the docs: - For KVM, `pauth` is a binary, "on" vs "off" option. The host CPU will choose the cryptographic algorithm. - For TCG, however, along with `pauth`, a couple of properties can be controlled -- they're are related to cryptographic algorithm choice. Thanks to Peter Maydell and Marc Zyngier for explaining more about PAuth on IRC (#qemu, OFTC). Signed-off-by: Kashyap Chamarthy --- v2: address Marc Zyngier's comments: https://lists.gnu.org/archive/html/qemu-devel/2025-01/msg03451.html --- docs/system/arm/cpu-features.rst | 46 +++++++++++++++++++++++++++++--- 1 file changed, 42 insertions(+), 4 deletions(-) diff --git a/docs/system/arm/cpu-features.rst b/docs/system/arm/cpu-feature= s.rst index a596316384..94d260b573 100644 --- a/docs/system/arm/cpu-features.rst +++ b/docs/system/arm/cpu-features.rst @@ -204,11 +204,49 @@ the list of KVM vCPU features and their descriptions. the guest scheduler behavior and/or be exposed to the guest userspace. =20 -TCG vCPU Features -=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D +"PAuth" (Pointer Authentication) +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D + +PAuth (Pointer Authentication) is a security feature in software that +was introduced in Armv8.3-A. It aims to protect against ROP +(return-oriented programming) attacks. + +KVM +--- + +``pauth`` + + Enable or disable ``FEAT_Pauth``. No other properties can be + controlled. + + The host CPU will define the PAC (pointer authentication + code) cryptographic algorithm. + + There are different "levels" of PAuth support. The host CPU + definition will define that level (e.g. PAuth, EPAC, PAuth2, FPAC, + FPACCOMBINE, etc). Refer to the Arm architecture extension documents + for details about the description of these features. + +Live migration and PAuth +~~~~~~~~~~~~~~~~~~~~~~~~ + +The level of PAuth support depends on which Arm architecture a given CPU +supports (e.g. Armv8.3 vs. Armv8.6). This gradation in PAuth support +has implications for live migration. For example, to be able to +live-migrate from host-A (with Armv8.3) to host-B (with Arm v8.6): + + - the source and destination hosts must "agree" on (a) the PAC + signature algorithm, and (b) all the sub-features of PAuth; or + + - the alternative (and less desirable) option is to turn off PAuth + off on both source and destination \ufffd\ufffd\ufffd this is generall= y not + recommended, as PAuth is a security feature. + +TCG +--- =20 -TCG vCPU features are CPU features that are specific to TCG. -Below is the list of TCG vCPU features and their descriptions. +For TCG, along with ``pauth``, it is possible to control a few other +properties of PAuth: =20 ``pauth`` Enable or disable ``FEAT_Pauth`` entirely. --=20 2.48.1