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 lists1p.gnu.org (lists1p.gnu.org [209.51.188.17]) (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 89B7EC44539 for ; Wed, 22 Jul 2026 14:49:02 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1wmYFb-00033c-KZ; Wed, 22 Jul 2026 10:48:47 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists1p.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1wmYFZ-00032O-LG for qemu-devel@nongnu.org; Wed, 22 Jul 2026 10:48:45 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1wmYFW-0005gP-6a for qemu-devel@nongnu.org; Wed, 22 Jul 2026 10:48:45 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1784731720; h=from:from:reply-to: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=TgefLV8N1+rGjPGNdeUplYaiOqA75UHVzp4fw9oKrYY=; b=IyTqeMhqNZcnA+7XJmaQtnyRIuEPcOVBim9TqVIk8AW28+QqRpXJa8Ec3CC4KaQNRFTxq+ Ac6xYCs6+8wNGQhoUZEIp9hAbgvvtPTQ5Gvl/4p8vm7ar+NO4Gx6B1VeAVrHVjql7NDEns w068MiM7KfJmzgyzx2uI1T/2HWOHoaY= Received: from mx-prod-mc-03.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-340-KutyO3lMPdCrJ9-0_PQPtg-1; Wed, 22 Jul 2026 10:48:37 -0400 X-MC-Unique: KutyO3lMPdCrJ9-0_PQPtg-1 X-Mimecast-MFC-AGG-ID: KutyO3lMPdCrJ9-0_PQPtg_1784731716 Received: from mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.93]) (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-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 521891977010; Wed, 22 Jul 2026 14:48:36 +0000 (UTC) Received: from redhat.com (unknown [10.44.49.82]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 8589C1800982; Wed, 22 Jul 2026 14:48:33 +0000 (UTC) Date: Wed, 22 Jul 2026 15:48:29 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: qemu-devel@nongnu.org Cc: Thomas Huth , Pierrick Bouvier , devel@lists.libvirt.org, =?utf-8?Q?Marc-Andr=C3=A9?= Lureau , Paolo Bonzini , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= Subject: Re: [PATCH for 11.1] crypto: deprecate the AF_ALG crypto backend Message-ID: References: <20260722115701.716516-1-berrange@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20260722115701.716516-1-berrange@redhat.com> User-Agent: Mutt/2.4.0 (2026-06-19) X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 Received-SPF: permerror client-ip=170.10.133.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: 12 X-Spam_score: 1.2 X-Spam_bar: + X-Spam_report: (1.2 / 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, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, RCVD_IN_SBL_CSS=3.335, SPF_HELO_PASS=-0.001, T_SPF_PERMERROR=0.01 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Wed, Jul 22, 2026 at 12:57:00PM +0100, Daniel P. Berrangé wrote: > Linux 7.1 has deprecated the AF_ALG crypto backend: ^^^^ should say 7.2 and likewise later in the patch > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=a67afb1884ba815079bd43d5c998e155e03b08b6 > > And has documented it to be always slower than userspace crypto: > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=5624ea54f3ba5c83d2e5503411a31a8be0278c1e > > as a result of dropping support for zero-copy and hardware > accelerators: > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7524070f26d8d347c26787dc297fb844baa26abf > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ffdd2bc378953b525aca61902534e753f1f8e734 > > The main use case for the AF_ALG impl was to improve the performance > of virtio-crypto with the cryptodev-backend-builtin driver. In > practice this did not matter since 'cryptodev-backend-lkcf' can do > offload to the kernel via the keyctl syscall, and 'cryptodev-vhost-user' > can offload to an external process which can optionally integrate with > hardware accelerators without kernel assistance. > > The AF_ALG backend has no user visible configuration options at runtime, > it is unconditionally tried with any use of the cipher APIs. So it does > not strictly have to go through the deprecation process, however, it is > left available initially in case there was an unexpected use case that > relies on it which may be faster with old kernels before the above Linux > commits. > > Suggested-by: Thomas Huth > Signed-off-by: Daniel P. Berrangé > --- > docs/about/deprecated.rst | 21 +++++++++++++++++++++ > meson.build | 6 ++++++ > 2 files changed, 27 insertions(+) > > diff --git a/docs/about/deprecated.rst b/docs/about/deprecated.rst > index 0c656a968f..54b2662752 100644 > --- a/docs/about/deprecated.rst > +++ b/docs/about/deprecated.rst > @@ -416,6 +416,27 @@ ABI is long-obsolete. We are therefore deprecating both OABI support > and NWFPE emulation, and they will be removed in a future QEMU > release. > > +Build features > +-------------- > + > +Crypto AF_ALG backend > +--------------------- > + > +The use of the AF_ALG backend for cryptography has been deprecated > +with no replacement. > + > +The AF_ALG interface is deprecated by Linux 7.1 and all support > +for hardware accelerators has been removed. It will thus always be > +slower than userspace crypto due to the overhead of copying data > +to kernel space. The GNUTLS, Nettle and GCrypt libraries supported > +by QEMU all include a variety of hardware optimized crypto > +implementations which should suffice for typical needs. > + > +For the virtio-crypto device, the 'cryptodev-backend-lkcf' backend > +can offload some operations to the kernel via the keyctl syscall, > +and the 'cryptodev-vhost-user' backend can offload the device > +backend to an external process which can integrate with crypto > +accelerators. > > Backwards compatibility > ----------------------- > diff --git a/meson.build b/meson.build > index 164328ded8..02cbe6445a 100644 > --- a/meson.build > +++ b/meson.build > @@ -5053,3 +5053,9 @@ if not actually_reloc and (host_os == 'windows' or get_option('relocatable')) > message('QEMU will have to be installed under ' + get_option('prefix') + '.') > message('Use --disable-relocatable to remove this warning.') > endif > + > +if get_option('crypto_afalg').enabled() > + warning('Use of the AF_ALG crypto backend is deprecated, ' + > + 'since Linux 7.1 has deprecated the AF_ALG interface ' + > + 'and removed its ability to use hardware accelerators.') > +endif > -- > 2.55.0 > With regards, Daniel -- |: https://berrange.com ~~ https://hachyderm.io/@berrange :| |: https://libvirt.org ~~ https://entangle-photo.org :| |: https://pixelfed.art/berrange ~~ https://fstop138.berrange.com :|