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 CF6FCC433EF for ; Thu, 12 May 2022 23:21:41 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 3B6DA6B0073; Thu, 12 May 2022 19:21:41 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 3646F6B0075; Thu, 12 May 2022 19:21:41 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 22E348D0001; Thu, 12 May 2022 19:21:41 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 10AB96B0073 for ; Thu, 12 May 2022 19:21:41 -0400 (EDT) Received: from smtpin29.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay13.hostedemail.com (Postfix) with ESMTP id CF61660910 for ; Thu, 12 May 2022 23:21:40 +0000 (UTC) X-FDA: 79458665160.29.78F0DA4 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by imf27.hostedemail.com (Postfix) with ESMTP id DF99B4009B for ; Thu, 12 May 2022 23:21:37 +0000 (UTC) From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1652397697; 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=84nnGwOoFOoUcIxrrghgkTUTltsimr0GgYwQOdT0EGI=; b=STHTVqqacHev1YK2lxR+88OX4pXem4AVJ+3cV57dbs7q198GyRICOjlvUEkZ28dtOvuHdn dRNnAN+0bJaqGSZYgeSUI3V2xJybQ4ro5kNpkxtm4i8cLgQd9oZQRUOyXsGig+2v/OvypW +fBv/bru6QOH9kVzqrzZf8bo8F9eSoNvTzMHRzjt48EFCiEnRfOtkYtU0LqJbA8GO6sMQw Xg+5+76Uv9RAWhOZzvVtuGX4YCDUC+MJ1QbrbEFNSxu1RFJtoL0iJk3WFNdascOnZ0yut8 vHJz9FeQmCQlk3GGyHwKa2WhKaAHwa7TFlB+4tXHLx7Qxwfu00mjShFC+aCUbA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1652397697; 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=84nnGwOoFOoUcIxrrghgkTUTltsimr0GgYwQOdT0EGI=; b=J3yuVJUipub7m7ga0YJBYUg1KC+UBuAK7jpcyV2djuXgkdLPh/8H7UU7Lgg53y/MBxx1wY /WfNbkxjab5esnBg== To: "Kirill A. Shutemov" , Dmitry Vyukov Cc: Peter Zijlstra , Dave Hansen , Andy Lutomirski , x86@kernel.org, Alexander Potapenko , "H . J . Lu" , Andi Kleen , Rick Edgecombe , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [RFCv2 00/10] Linear Address Masking enabling In-Reply-To: <878rr6v985.ffs@tglx> References: <20220511022751.65540-1-kirill.shutemov@linux.intel.com> <20220511064943.GR76023@worktop.programming.kicks-ass.net> <87pmkivjst.ffs@tglx> <20220512165612.gizedzgtpzbi7jbl@black.fi.intel.com> <878rr6v985.ffs@tglx> Date: Fri, 13 May 2022 01:21:37 +0200 Message-ID: <87r14ytjzy.ffs@tglx> MIME-Version: 1.0 Content-Type: text/plain Authentication-Results: imf27.hostedemail.com; dkim=pass header.d=linutronix.de header.s=2020 header.b=STHTVqqa; dkim=pass header.d=linutronix.de header.s=2020e header.b=J3yuVJUi; spf=pass (imf27.hostedemail.com: domain of tglx@linutronix.de designates 193.142.43.55 as permitted sender) smtp.mailfrom=tglx@linutronix.de; dmarc=pass (policy=none) header.from=linutronix.de X-Rspam-User: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: DF99B4009B X-Stat-Signature: 5ez1bffkwp73t9kskokfpfeuffbe3wcx X-HE-Tag: 1652397697-88011 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 21:31, Thomas Gleixner wrote: > On Thu, May 12 2022 at 19:56, Kirill A. Shutemov wrote: >> On Thu, May 12, 2022 at 05:42:58PM +0200, Thomas Gleixner wrote: >>> On Wed, May 11 2022 at 08:49, Peter Zijlstra wrote: >>> > On Wed, May 11, 2022 at 05:27:40AM +0300, Kirill A. Shutemov wrote: >>> > So aren't we creating a problem with LAM_U48 where programs relying on >>> > it are of limited sustainability? >>> > >>> > Any such program simply *cannot* run on 5 level pagetables. Why do we >>> > want to do this? >>> >>> More bits are better :) >>> >>> Seriously, I agree that restricting it to LAM57, which gives us 6 bits, >>> makes a lot of sense _and_ makes the whole thing way simpler. >>> >>> So supporting both needs a truly good justification and a real world use >>> case. >> >> I asked the question before[1]. Basically, more bits more better: >> >> For HWASAN #bits == detection probability. >> For MarkUS #bits == exponential cost reduction > > What is MarkUS? It's not really helpful to provide acronyms which are > not decodable. > >> I would really like to have only LAM_U57, but IIUC 6 bits is not always >> enough. >> >> Dmitry, could you elaborate? >> >> [1] https://mobile.twitter.com/dvyukov/status/1342019823400837120 > > I don't know whether he reacts on posting a link to his twitter > account. I've CC'ed him now. Maybe that works better. Duh. I should have looked at 'To:' and not only at 'Cc:' Maybe someday I get used to this email thing. Thanks, tglx