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 510D5C43334 for ; Tue, 12 Jul 2022 17:14:46 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id B47D69400B7; Tue, 12 Jul 2022 13:14:45 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id AD11F940063; Tue, 12 Jul 2022 13:14:45 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 972B89400B7; Tue, 12 Jul 2022 13:14:45 -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 7FBDE940063 for ; Tue, 12 Jul 2022 13:14:45 -0400 (EDT) Received: from smtpin18.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay11.hostedemail.com (Postfix) with ESMTP id 533C58023B for ; Tue, 12 Jul 2022 17:14:45 +0000 (UTC) X-FDA: 79679097330.18.9FC39E8 Received: from mga05.intel.com (mga05.intel.com [192.55.52.43]) by imf13.hostedemail.com (Postfix) with ESMTP id 8E49D2006E for ; Tue, 12 Jul 2022 17:14:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1657646083; x=1689182083; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=8RMeG8zscE7DyFRKmEbCnGAL3Id+0MlNRoW2dx79+/U=; b=hdgnwfR7JGh7aLE4y7QWupPb5CR6iT6HAsbPZ6Jetm2Pgkr55nzeJ/9M 5Bar/WS2QdAJvGnjV8/7+Rd42HihiFPY4tOx8SI8VMnkhO/u7hj5NwSQI ApDiSAjv5rst87S0KRW4qhF7DZidRTxsVHbhV58jwtTTF6z7MynuDGIBU v9cJ3DCS61o877184ahKddxa3jNDF0ry2JpKx3jFLPDlY/N+mZ68KZWcR kkZ3+p7oJtPyjttL72avUcFbtgmNV8P6IkJXUQ6hYl1srtNmNs/SGd4M/ I5hi1kyANaj3ueYXKsuIi6MgaVjinYnu6clmFtoc4jNdAJDLwP4HmnUzi w==; X-IronPort-AV: E=McAfee;i="6400,9594,10406"; a="371305796" X-IronPort-AV: E=Sophos;i="5.92,266,1650956400"; d="scan'208";a="371305796" Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 12 Jul 2022 10:14:41 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.92,266,1650956400"; d="scan'208";a="663028079" Received: from black.fi.intel.com ([10.237.72.28]) by fmsmga004.fm.intel.com with ESMTP; 12 Jul 2022 10:14:38 -0700 Received: by black.fi.intel.com (Postfix, from userid 1000) id 442FDF1; Tue, 12 Jul 2022 20:14:46 +0300 (EEST) Date: Tue, 12 Jul 2022 20:14:45 +0300 From: "Kirill A. Shutemov" To: Alexander Potapenko Cc: Dave Hansen , Andy Lutomirski , Peter Zijlstra , the arch/x86 maintainers , Kostya Serebryany , Andrey Ryabinin , Andrey Konovalov , Dmitry Vyukov , "H . J . Lu" , Andi Kleen , Rick Edgecombe , Linux Memory Management List , LKML Subject: Re: [PATCHv4 6/8] x86/mm: Provide ARCH_GET_UNTAG_MASK and ARCH_ENABLE_TAGGED_ADDR Message-ID: <20220712171445.74b46mgdxgaub3qj@black.fi.intel.com> References: <20220622162230.83474-1-kirill.shutemov@linux.intel.com> <20220622162230.83474-7-kirill.shutemov@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1657646084; a=rsa-sha256; cv=none; b=YCEPHJSgGwtJjKysKdA4tLMlcMbumw4jj6uBbs/PyUAvjbXIZkdYCngjeiaU0Hbqmt8KBS SuQ4WVRCpwCXB3cCMX98S8xGKlu49wBASyX2GCP7F0+/envcMiGNZLz7AU+KOlHYJdZ8oi HkfiTXTnnt8CnYkhJqHM8CsYOLavsOU= ARC-Authentication-Results: i=1; imf13.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=hdgnwfR7; dmarc=pass (policy=none) header.from=intel.com; spf=none (imf13.hostedemail.com: domain of kirill.shutemov@linux.intel.com has no SPF policy when checking 192.55.52.43) smtp.mailfrom=kirill.shutemov@linux.intel.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1657646084; 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=S4BAoUjNPczsjsxTXEF7V/7f/cvfOhl3/KaVNkd7iQk=; b=hWxmtaOWVOL7Snh10DPbhv+IURYuW1y2oEJQkx4K/SaJTP5cCRpEpD9ltfpzhA4Dsitf/Y LDMonkqANIT472K27XSLOpGbbFlPyCkjgVXmCAmzEvA5Feg4fxRu8xXUtPDUkLHF7TuSPW TKgs8x6jO1oxPdCEsfZgm9B8LYlbUFI= Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=hdgnwfR7; dmarc=pass (policy=none) header.from=intel.com; spf=none (imf13.hostedemail.com: domain of kirill.shutemov@linux.intel.com has no SPF policy when checking 192.55.52.43) smtp.mailfrom=kirill.shutemov@linux.intel.com X-Rspam-User: X-Stat-Signature: zmzxbt59qfj98k6dz7saefsoqyfw93jk X-Rspamd-Queue-Id: 8E49D2006E X-Rspamd-Server: rspam08 X-HE-Tag: 1657646083-872023 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 Tue, Jul 12, 2022 at 03:12:01PM +0200, Alexander Potapenko wrote: > On Wed, Jun 22, 2022 at 6:22 PM Kirill A. Shutemov > wrote: > > > > Add a couple of arch_prctl() handles: > > > > - ARCH_ENABLE_TAGGED_ADDR enabled LAM. The argument is required number > > of tag bits. It is rounded up to the nearest LAM mode that can > > provide it. For now only LAM_U57 is supported, with 6 tag bits. > > > > - ARCH_GET_UNTAG_MASK returns untag mask. It can indicates where tag > > bits located in the address. > > > Am I right that the desired way to detect the presence of LAM without > enabling it is to check that arch_prctl(ARCH_GET_UNTAG_MASK, ...) > returns zero? Returns -1UL, but yes. > Overall, I think these new arch_prctls should be documented following > the spirit of PR_SET_TAGGED_ADDR_CTRL/PR_GET_TAGGED_ADDR_CTRL > somewhere. The plan is to update man page for the syscall once the interface is upstream. > > + > > +static int prctl_enable_tagged_addr(struct mm_struct *mm, unsigned long nr_bits) > > +{ > > + int ret = 0; > > + > > + if (!cpu_feature_enabled(X86_FEATURE_LAM)) > > + return -ENODEV; > > + > > + mutex_lock(&mm->context.lock); > > + > > + /* Already enabled? */ > > + if (mm->context.lam_cr3_mask) { > > + ret = -EBUSY; > > + goto out; > > + } > > + > > + if (!nr_bits) { > > + ret = -EINVAL; > > One would expect that `arch_prctl(ARCH_ENABLE_TAGGED_ADDR, 0)` > disables tagging for the current process. > Shouldn't this workflow be supported as well? Is there an use-case for it? I would rather keep the interface minimal. We can always add this in the future if an use-case comes. -- Kirill A. Shutemov