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 BC797C3526D for ; Wed, 26 Jan 2022 13:39:18 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id E80446B0073; Wed, 26 Jan 2022 08:39:17 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id E303B6B0074; Wed, 26 Jan 2022 08:39:17 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D1E316B0075; Wed, 26 Jan 2022 08:39:17 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0120.hostedemail.com [216.40.44.120]) by kanga.kvack.org (Postfix) with ESMTP id C27706B0073 for ; Wed, 26 Jan 2022 08:39:17 -0500 (EST) Received: from smtpin20.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 8568F944FE for ; Wed, 26 Jan 2022 13:39:17 +0000 (UTC) X-FDA: 79072544754.20.75EA0C8 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf13.hostedemail.com (Postfix) with ESMTP id B604220032 for ; Wed, 26 Jan 2022 13:39:16 +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=j3mxqba4lJDf0RPplJMQZZKNpeYszCRsoXdpeIzlqG0=; b=aFQ57o3xObWckwSj3FOIpyUQdD A6K24Xwi7js7rprKwslmoaHnxVAzmc4vuzBdCneEN8VlJhoJ0t9M1CG86bYf0WJeSuGs8EQdD/iq7 58lgsejIvm/9M7bds0TmyJKb0/ohvJG6qrwSe9eoSxwFu5bz9oMQip9jmrAf36++2Aoy7un39C2+G tFyuHL+cCQKlr1yUzvtYTNXAbKUGiiFAoEQrwKLdx8zf99ESymVdOpBEhf78jbMlVww8oCp4m0nrM Nb4ONUM/fq2wo69UZmKjTKJHx6pjKsRyJpx0506AKFl1iWfXDFNGWVY8eZGa9oD4GYdJnFH0HyY+/ yfk1WNvw==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1nCiVd-0045DA-GF; Wed, 26 Jan 2022 13:38:49 +0000 Date: Wed, 26 Jan 2022 13:38:49 +0000 From: Matthew Wilcox To: David Hildenbrand Cc: "Kirill A. Shutemov" , Khalid Aziz , akpm@linux-foundation.org, longpeng2@huawei.com, arnd@arndb.de, dave.hansen@linux.intel.com, rppt@kernel.org, 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-Queue-Id: B604220032 X-Rspam-User: nil Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=aFQ57o3x; dmarc=none; spf=none (imf13.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org X-Stat-Signature: s98ijeq5d3nuct1tfpy1f7pnq9k7hiah X-Rspamd-Server: rspam08 X-HE-Tag: 1643204356-61271 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000785, 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 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.