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 5668FC28CF5 for ; Wed, 26 Jan 2022 14:12:49 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id B00BB6B0073; Wed, 26 Jan 2022 09:12:48 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id AAE7C6B0074; Wed, 26 Jan 2022 09:12:48 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 99D976B0075; Wed, 26 Jan 2022 09:12:48 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0024.hostedemail.com [216.40.44.24]) by kanga.kvack.org (Postfix) with ESMTP id 8A0EC6B0073 for ; Wed, 26 Jan 2022 09:12:48 -0500 (EST) Received: from smtpin29.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 3F78B181CAC5F for ; Wed, 26 Jan 2022 14:12:48 +0000 (UTC) X-FDA: 79072629216.29.CE154A9 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by imf30.hostedemail.com (Postfix) with ESMTP id 6E8D180098 for ; Wed, 26 Jan 2022 14:12:33 +0000 (UTC) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 073B16173B; Wed, 26 Jan 2022 14:12:31 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id CE388C340E3; Wed, 26 Jan 2022 14:12:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1643206350; bh=PdD13NpHQIo3/NEcjNLN+uTWme5k/O++wX4lnajZwU0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Xpud2vg+AejkJT2px+KGeKsdG1ae+aYX9Ru4yyyjTdr+wAx/JMiPVnjjhiIz8DWCe 9q9U3vX3ESpkdWx5urk8phTD9MLjPGXbJHoXTeutOk5+wLFG4J5CylEFYbcchR6POo VgwDhqfwEPraF6B185ILy2K5dP2C59mniHDAwQJjP+uF1sWM3pqfCcEJF8pDGM3zRg Ie/rzIDQ2cOs3rgdusoe79ypI9P27nfiT0IuudKiwBH8sM04YiwZC/+tNqt9UdknCE ldbYAcxpxsm+tGa3jsX/KSbFTWhTh1EquXomi0OGNpBmStzGYffso1KCfyDrHAf1IF JIlvUhxZ0r47w== Date: Wed, 26 Jan 2022 16:12:18 +0200 From: Mike Rapoport To: Matthew Wilcox Cc: David Hildenbrand , "Kirill A. Shutemov" , Khalid Aziz , akpm@linux-foundation.org, longpeng2@huawei.com, arnd@arndb.de, dave.hansen@linux.intel.com, surenb@google.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Peter Xu Subject: Re: [RFC PATCH 0/6] Add support for shared PTEs across processes Message-ID: References: <20220125114212.ks2qtncaahi6foan@box.shutemov.name> <20220125135917.ezi6itozrchsdcxg@box.shutemov.name> <20220125185705.wf7p2l77vggipfry@box.shutemov.name> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 6E8D180098 X-Stat-Signature: wb7gwk43cdxxkonxajjnctzdso41tynz X-Rspam-User: nil Authentication-Results: imf30.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=Xpud2vg+; spf=pass (imf30.hostedemail.com: domain of rppt@kernel.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=rppt@kernel.org; dmarc=pass (policy=none) header.from=kernel.org X-HE-Tag: 1643206353-204545 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000004, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Jan 26, 2022 at 01:38:49PM +0000, Matthew Wilcox wrote: > On Wed, Jan 26, 2022 at 11:16:42AM +0100, David Hildenbrand wrote: > > A while ago I talked with Peter about an extended uffd (here: WP) > > mechanism that would work on fds instead of the process address space. > > As far as I can tell, uffd is a grotesque hack that exists to work around > the poor choice to use anonymous memory instead of file-backed memory > in kvm. Every time I see somebody mention it, I feel pain. How file-backed memory would have helped for the major use-case of uffd which is post-copy migration? -- Sincerely yours, Mike.