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 81C30C433EF for ; Fri, 13 May 2022 03:05:31 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id DDD136B0073; Thu, 12 May 2022 23:05:30 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id D632F6B0075; Thu, 12 May 2022 23:05:30 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C06206B0078; Thu, 12 May 2022 23:05:30 -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 AF2E56B0073 for ; Thu, 12 May 2022 23:05:30 -0400 (EDT) Received: from smtpin13.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id 7FD6831C3B for ; Fri, 13 May 2022 03:05:30 +0000 (UTC) X-FDA: 79459229220.13.A6919D1 Received: from mga17.intel.com (mga17.intel.com [192.55.52.151]) by imf25.hostedemail.com (Postfix) with ESMTP id 46A2AA009B for ; Fri, 13 May 2022 03:05:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1652411129; x=1683947129; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=RKmc/JYK4Flm5C6llb5dgyed83U7HDxdTph4z1wb4ys=; b=bEMlHgQcnLhP5IPKjmvjXXaX9B9E3lwqgMcwtx9g+f2SnWY9DsqkkC9s FVsUKPVF64svbqUxcqEG4mzb092czMRdFVY/TWvSPrpaDAMSdNi6666ag OXIF4aJ30QG6C90aLkunmuRK8KFL9YMsOMP4ynpj1Ucfbnb3Dh9D/gy// mvHcqjpmYGZp1acVXA8AXXAmSPmyjdm3bvBDgazO6tW0kb0bq/OlGTTiV xnPkB85kcDWO0Gnr28W5VBw/n7+ru7cu1qaI10O0HMfobTnaBl8kRTDJJ E+e3ui6vatDGgoymVURm9RtT5BMQ8oQzsTKV/89HdqXgMQ0+4wZb4s9ix A==; X-IronPort-AV: E=McAfee;i="6400,9594,10345"; a="250731136" X-IronPort-AV: E=Sophos;i="5.91,221,1647327600"; d="scan'208";a="250731136" Received: from fmsmga007.fm.intel.com ([10.253.24.52]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 12 May 2022 20:05:28 -0700 X-IronPort-AV: E=Sophos;i="5.91,221,1647327600"; d="scan'208";a="572793934" Received: from wdwickar-mobl1.amr.corp.intel.com (HELO [10.252.130.245]) ([10.252.130.245]) by fmsmga007-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 12 May 2022 20:05:27 -0700 Message-ID: Date: Thu, 12 May 2022 20:05:26 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.8.1 Subject: Re: [RFCv2 00/10] Linear Address Masking enabling Content-Language: en-US To: Thomas Gleixner , "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 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> From: Dave Hansen In-Reply-To: <878rr6te6b.ffs@tglx> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: ssrq7wuua7b9n5ao1cbq97ox8rtc5gu4 X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 46A2AA009B X-Rspam-User: Authentication-Results: imf25.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=bEMlHgQc; dmarc=pass (policy=none) header.from=intel.com; spf=none (imf25.hostedemail.com: domain of dave.hansen@intel.com has no SPF policy when checking 192.55.52.151) smtp.mailfrom=dave.hansen@intel.com X-HE-Tag: 1652411110-984537 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 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/