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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id F20C7C4332F for ; Wed, 12 Oct 2022 12:19:09 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 4A5836B0071; Wed, 12 Oct 2022 08:19:09 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 4560C6B0073; Wed, 12 Oct 2022 08:19:09 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2F5806B0074; Wed, 12 Oct 2022 08:19:09 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id 1C2156B0071 for ; Wed, 12 Oct 2022 08:19:09 -0400 (EDT) Received: from smtpin09.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id D8E7012055F for ; Wed, 12 Oct 2022 12:19:08 +0000 (UTC) X-FDA: 80012201976.09.BEC4967 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by imf16.hostedemail.com (Postfix) with ESMTP id 25B4D18001E for ; Wed, 12 Oct 2022 12:19:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1665577147; 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: in-reply-to:in-reply-to:references:references; bh=NV9CicB0DRH4ogY4pUsl7yjoSLbllPXxF4kP6gpANzQ=; b=ZkdFf4RSyplWIFAZsiTBd1eC38yxC4jqCcTmT2b2alQ3A3NN3PoyHHda7lfpms+UpCV42o YinuqKnTn2KnnTI3pA1PMZ8gm6RDgUXPy9ShiVq+ARkciW4TcK1ASiuVoCZHFaP726PPqc t1XN8hCIg5p+27MIUNYYcvPVvk6wOaQ= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-83-Mfy2mdPFOvymBf8YsiyteA-1; Wed, 12 Oct 2022 08:19:04 -0400 X-MC-Unique: Mfy2mdPFOvymBf8YsiyteA-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 526D8811E75; Wed, 12 Oct 2022 12:19:02 +0000 (UTC) Received: from oldenburg.str.redhat.com (unknown [10.39.192.47]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 5D68C414A809; Wed, 12 Oct 2022 12:18:54 +0000 (UTC) From: Florian Weimer To: "Edgecombe, Rick P" Cc: "bsingharora@gmail.com" , "hpa@zytor.com" , "Syromiatnikov, Eugene" , "peterz@infradead.org" , "rdunlap@infradead.org" , "keescook@chromium.org" , "dave.hansen@linux.intel.com" , "kirill.shutemov@linux.intel.com" , "Eranian, Stephane" , "linux-mm@kvack.org" , "nadav.amit@gmail.com" , "jannh@google.com" , "dethoma@microsoft.com" , "linux-arch@vger.kernel.org" , "kcc@google.com" , "bp@alien8.de" , "oleg@redhat.com" , "hjl.tools@gmail.com" , "Yang, Weijiang" , "Lutomirski, Andy" , "pavel@ucw.cz" , "arnd@arndb.de" , "Moreira, Joao" , "tglx@linutronix.de" , "mike.kravetz@oracle.com" , "x86@kernel.org" , "linux-doc@vger.kernel.org" , "jamorris@linux.microsoft.com" , "john.allen@amd.com" , "rppt@kernel.org" , "mingo@redhat.com" , "Shankar, Ravi V" , "corbet@lwn.net" , "linux-kernel@vger.kernel.org" , "linux-api@vger.kernel.org" , "gorcunov@gmail.com" Subject: Re: [PATCH v2 23/39] x86: Introduce userspace API for CET enabling References: <20220929222936.14584-1-rick.p.edgecombe@intel.com> <20220929222936.14584-24-rick.p.edgecombe@intel.com> <87v8os0wx5.fsf@oldenburg.str.redhat.com> <8599719452d9615235f7fdd274a9b6ea04ab1f7c.camel@intel.com> Date: Wed, 12 Oct 2022 14:18:52 +0200 In-Reply-To: <8599719452d9615235f7fdd274a9b6ea04ab1f7c.camel@intel.com> (Rick P. Edgecombe's message of "Mon, 10 Oct 2022 16:28:57 +0000") Message-ID: <87zge1z13n.fsf@oldenburg.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.1 on 10.11.54.2 ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1665577148; h=from:from:sender: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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=NV9CicB0DRH4ogY4pUsl7yjoSLbllPXxF4kP6gpANzQ=; b=EtAJ+FVgAW9+Uv4wV40TGMh0JaUPl8o98isYeqBnP62fRWWdU4lBQ57yyYFWYbodSSVbI0 F5juWbbxXwO7HpBUZRtYVot9Rn/w4nkIEJiLOALLUH2nsxOZkhE/o4GjxGLtI0rIPjB3Fg 1DAJ9o+L8pg2etLKrA6O+vwsHdLPTQg= ARC-Authentication-Results: i=1; imf16.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=ZkdFf4RS; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf16.hostedemail.com: domain of fweimer@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=fweimer@redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1665577148; a=rsa-sha256; cv=none; b=lWzTYAolv08DoJaRYHXSNQLEJKaYW7MHGDPVBlsulKZ3r6jDpD/3w7EuKIs3/GCgE/8Dbd Q1I1pj10EUYPKjdD/KRMET/P7WYhjTOcSM88JLfObpUIk7jPN+61syYSdP07SB5S2hDnfL SBiI/7wWCwFXv7/fSGDWT7TQK7k2JUs= X-Stat-Signature: u89fd4w8hodrzo3nk8ekapigohm4ky7a X-Rspamd-Queue-Id: 25B4D18001E Authentication-Results: imf16.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=ZkdFf4RS; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf16.hostedemail.com: domain of fweimer@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=fweimer@redhat.com X-Rspam-User: X-Rspamd-Server: rspam12 X-HE-Tag: 1665577147-205540 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: * Rick P. Edgecombe: > On Mon, 2022-10-10 at 12:56 +0200, Florian Weimer wrote: >> > + /* Only support enabling/disabling one feature at a time. */ >> > + if (hweight_long(features) > 1) >> > + return -EINVAL; >> >> This means we'll soon need three extra system calls for x86-64 >> process >> start: SHSTK, IBT, and switching off vsyscall emulation. (The latter >> does not need any special CPU support.) >> >> Maybe we can do something else instead to make the strace output a >> little bit cleaner? > > In previous versions it supported enabling multiple features in a > single syscall. Thomas Gleixner pointed out that (this was on the LAM > patchset that shared the interface at the time) it makes the behavior > of what to do when one feature fails to enable complicated: > > https://lore.kernel.org/lkml/87zgjjqico.ffs@tglx/ Can we return the bits for the features that were actually enabled? Those three don't have cross-dependencies in the sense that you would only use X & Y together, but not X or Y alone. Thanks, Florian