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 EA49AC433F5 for ; Tue, 18 Jan 2022 21:47:04 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 6AB136B0072; Tue, 18 Jan 2022 16:47:04 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 659876B0073; Tue, 18 Jan 2022 16:47:04 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 521AB6B0074; Tue, 18 Jan 2022 16:47:04 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0079.hostedemail.com [216.40.44.79]) by kanga.kvack.org (Postfix) with ESMTP id 42E416B0072 for ; Tue, 18 Jan 2022 16:47:04 -0500 (EST) Received: from smtpin17.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id ED16A824C420 for ; Tue, 18 Jan 2022 21:47:03 +0000 (UTC) X-FDA: 79044743526.17.59C2CFD Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf05.hostedemail.com (Postfix) with ESMTP id 0ECB2100003 for ; Tue, 18 Jan 2022 21:47:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=o8OmDpmZwJ79TFW9weYPQvWllvtuDgUzn/OlUeFCC2k=; b=AtOJQ8qYFVQN9/o1R+g2yTBeJw t8JksLXBwJDcE3vigeGh6whgARjvfzSvxtz5i6xZ9/ixC4Vu1A9fj1y8J7TcXuvXrTPTH293A2+ns bZPV0SN0Nx+Ow+Eyi1WR6fIK6dDagBsXSDac7cWlBgbAstcotChhkyraCn9//sbMUyeJthLGTix4E 5EBg9ujXs2FrYaM6OJ/dWD9cv+O2zITmbJQI4729mku8KDzFp32nRW4En8FHH9oYqgOT94lQFDdPx bMshun3BuLSgJxo4lqPRbq4ppyWo+D/SrIKSbswrTK3C2MR9I960YGHN6I3UD1UVq+ZCgLzhP7x/3 FLTlLJ2A==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1n9wJF-009ZJO-63; Tue, 18 Jan 2022 21:46:33 +0000 Date: Tue, 18 Jan 2022 21:46:33 +0000 From: Matthew Wilcox To: Dave Hansen Cc: Khalid Aziz , akpm@linux-foundation.org, longpeng2@huawei.com, arnd@arndb.de, dave.hansen@linux.intel.com, david@redhat.com, rppt@kernel.org, surenb@google.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [RFC PATCH 0/6] Add support for shared PTEs across processes Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 0ECB2100003 X-Stat-Signature: 4thq83spi4pydxzn34qgxaohanmbmd7z Authentication-Results: imf05.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=AtOJQ8qY; spf=none (imf05.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org; dmarc=none X-HE-Tag: 1642542422-544464 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, Jan 18, 2022 at 01:41:40PM -0800, Dave Hansen wrote: > On 1/18/22 1:19 PM, Khalid Aziz wrote: > > - Starting address must be aligned to pgdir size (512GB on x86_64) > > How does this work on systems with 5-level paging where a top-level page > table entry covers 256TB? Is the alignment requirement 512GB or 256TB? > How does userspace figure out which alignment requirement it is subject to? The original idea was any power of two, naturally aligned, >= PAGE_SIZE, but I suspect Khalid has simplified it for this first implementation.