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 9B122C433F5 for ; Fri, 13 May 2022 08:28:36 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id E94A56B0073; Fri, 13 May 2022 04:28:35 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id E443C6B0075; Fri, 13 May 2022 04:28:35 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id CE6136B0078; Fri, 13 May 2022 04:28:35 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id BF55D6B0073 for ; Fri, 13 May 2022 04:28:35 -0400 (EDT) Received: from smtpin02.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 9773231EAE for ; Fri, 13 May 2022 08:28:35 +0000 (UTC) X-FDA: 79460043390.02.413B18B Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by imf13.hostedemail.com (Postfix) with ESMTP id 23133200AA for ; Fri, 13 May 2022 08:28:15 +0000 (UTC) From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1652430512; 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=n7avP9kQVE0MWtOQvN65Uv2IDjaisxjzLPFA4LnZXoE=; b=cdUDCSQRLQffppm8ZF6ZF1WA7yW+Swl/SYpZ9kiy/4AhT8lN5StoZZa/EoaE62Mhzhajjo HUsq0BiYFpWvr6kJV488ml8O35G7Woweu/2RBaEx8IE/fY1zaB4PwIcF2d/Kvbi1AeJDTu +fxktLsUvuk2ITMbcWp0RQOioO4q7qipwiyR3NGcGwQ68g3XRxPHUxs4aC2bSJSnFpZMHR /ukfHmvwhS9DM8PGXGlh2yXzo7uzFFsUaIGqwVLTLASsZElLwgo3IXet63LK5iZsfVP6+Q zlDEWU3MbLGBwytDaNcjg3TVmmKm8jD9r9kcLY/FY/meD6qAcLukJ8riStELkA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1652430512; 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=n7avP9kQVE0MWtOQvN65Uv2IDjaisxjzLPFA4LnZXoE=; b=hWvzcLujdLspE9h0n+Lla1LSNSBaq0PRD+NI1vhmkbZrGHZcq/aa1QvGgiAQWJOjXJMzPm Sh51ecK3LMC/WzBQ== To: Dave Hansen , "H.J. Lu" Cc: Peter Zijlstra , "Kirill A. Shutemov" , Dave Hansen , Andy Lutomirski , the arch/x86 maintainers , Alexander Potapenko , Dmitry Vyukov , Andi Kleen , Rick Edgecombe , Linux-MM , Catalin Marinas , LKML Subject: Re: [RFCv2 00/10] Linear Address Masking enabling In-Reply-To: References: <20220511022751.65540-1-kirill.shutemov@linux.intel.com> <20220511064943.GR76023@worktop.programming.kicks-ass.net> <20bada85-9203-57f4-2502-57a6fd11f3ea@intel.com> <875ymav8ul.ffs@tglx> <55176b79-90af-4a47-dc06-9f5f2f2c123d@intel.com> <87o802tjd7.ffs@tglx> <67aef839-0757-37b1-a42d-154c0116cbf5@intel.com> <878rr6te6b.ffs@tglx> Date: Fri, 13 May 2022 10:28:31 +0200 Message-ID: <875ym9u98w.ffs@tglx> MIME-Version: 1.0 Content-Type: text/plain X-Stat-Signature: jyz6js9hrzosci548ecs48y1owk61cbz X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 23133200AA X-Rspam-User: Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=linutronix.de header.s=2020 header.b=cdUDCSQR; dkim=pass header.d=linutronix.de header.s=2020e header.b=hWvzcLuj; dmarc=pass (policy=none) header.from=linutronix.de; spf=pass (imf13.hostedemail.com: domain of tglx@linutronix.de designates 193.142.43.55 as permitted sender) smtp.mailfrom=tglx@linutronix.de X-HE-Tag: 1652430495-539227 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: On Thu, May 12 2022 at 20:05, Dave Hansen wrote: > On 5/12/22 18:27, Thomas Gleixner wrote: >> On Thu, May 12 2022 at 17:46, Dave Hansen wrote: >>> On 5/12/22 17:08, H.J. Lu wrote: >>> If I had to take a shot at this today, I think I'd opt for: >>> >>> mask = sys_enable_masking(bits=6, flags=FUZZY_NR_BITS); >>> >>> although I'm not super confident about the "fuzzy" flag. I also don't >>> think I'd totally hate the "blind" interface where the kernel just gets >>> to pick unilaterally and takes zero input from userspace. >> That's the only sane choice and you can make it simple for userspace: >> >> ret = prctl(GET_XXX_MASK, &mask); >> >> and then let it decide based on @ret and @mask whether to use it or not. >> >> But of course nobody thought about this as a generic feature and so we >> have the ARM64 TBI muck as a precedence. > > Well, not quite *nobody*: > > https://lore.kernel.org/linux-arm-kernel/7a34470c-73f0-26ac-e63d-161191d4b1e4@intel.com/ Sigh....