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 22C8EC32774 for ; Tue, 23 Aug 2022 05:43:21 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id AFA048D0003; Tue, 23 Aug 2022 01:43:20 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id AA9308D0001; Tue, 23 Aug 2022 01:43:20 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9BEF48D0003; Tue, 23 Aug 2022 01:43:20 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id 8C8BE8D0001 for ; Tue, 23 Aug 2022 01:43:20 -0400 (EDT) Received: from smtpin05.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 6023DC1409 for ; Tue, 23 Aug 2022 05:43:20 +0000 (UTC) X-FDA: 79829764560.05.CC25322 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf20.hostedemail.com (Postfix) with ESMTP id 5116C1C0016 for ; Tue, 23 Aug 2022 05:43:19 +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=NO0ifbcV0JwASDPMSKWX+lMLGTRG9S57tYDVHubceXI=; b=gKwRG50A+WPdWpJeXxK3pKfxZo 7WsKMgwaAweHTy0ymgj2pGxd6vGAs3zFuUawRp0u4d8rZriJ5O1meyLjdnbvogEIIJGeJPHdtqlXi T9otdL11/aNnHlzSP4txvEroFQ/yDUNJLMJ9+YzWZuk8GWTvV3RYnB7LMx/ySopVM0+moxnr5dWtt sk442+kbqvhw03tSc0i4BlWhhwwwxbnXW0kGZk97ZbrltZOX+ivT8pyEghhvLn4CXVXdo/sk9H4lO CZo3624uz86u9Ebo511wwZsHaayvSg/hSY+rpO+T5AUeIVSmzSqldpjy93xupvsuhxo22+bBqGBte VIXMEIAg==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=worktop.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1oQMgo-00EziM-0e; Tue, 23 Aug 2022 05:43:02 +0000 Received: by worktop.programming.kicks-ass.net (Postfix, from userid 1000) id 2851898049D; Tue, 23 Aug 2022 07:42:59 +0200 (CEST) Date: Tue, 23 Aug 2022 07:42:59 +0200 From: Peter Zijlstra To: Song Liu Cc: Linux-MM , lkml , Andrew Morton , X86 ML , Christoph Hellwig , Kernel Team , "Edgecombe, Rick P" , Luis Chamberlain , Dave Hansen , Song Liu Subject: Re: [RFC 0/5] vmalloc_exec for modules and BPF programs Message-ID: References: <20220818224218.2399791-1-song@kernel.org> <4D089469-B32B-4347-A811-B1E5EE011307@fb.com> <7621DE6E-D71D-45D1-BAFA-46E882451DD9@fb.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <7621DE6E-D71D-45D1-BAFA-46E882451DD9@fb.com> ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1661233400; 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=NO0ifbcV0JwASDPMSKWX+lMLGTRG9S57tYDVHubceXI=; b=6vlgAI1ArR8a2oZjCqBaS364BAO+BzdH+63n6BQklDQM0V+JGLP53bhZ1bYeOa088vhbeD OkU65A/d/wfwVSsM6nU86llbESn3/ea/3miOASXXPw89qBMZsDiHr637407cB29IPP8WLy TWwk3o+ObPjGSeNI1YHOg/eJ09vjjD4= ARC-Authentication-Results: i=1; imf20.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=gKwRG50A; spf=none (imf20.hostedemail.com: domain of peterz@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=peterz@infradead.org; dmarc=none ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1661233400; a=rsa-sha256; cv=none; b=Leof4mqNy5AJt1wHmzRBrV0HBWHHpXt8vDvlaKrVhTy9ggeD6mxsT3WY83VIxzRlnzvhht bD94SF8VYaqlCkO7X69FlA5Ja7DxWLPTO6L5z8C0YTE8stHfrw23NWVwxU3NfrIGAa2L5M 6xRZ4qfxwhD6xGd0gp2QuYDKcOza52E= X-Stat-Signature: dceo9wofr8uut3bfxjgrne6368jyk9b7 Authentication-Results: imf20.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=gKwRG50A; spf=none (imf20.hostedemail.com: domain of peterz@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=peterz@infradead.org; dmarc=none X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 5116C1C0016 X-Rspam-User: X-HE-Tag: 1661233399-970177 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 Mon, Aug 22, 2022 at 04:56:47PM +0000, Song Liu wrote: > > > > On Aug 22, 2022, at 9:34 AM, Peter Zijlstra wrote: > > > > On Mon, Aug 22, 2022 at 03:46:38PM +0000, Song Liu wrote: > >> Could you please share your feedback on this? > > > > I've looked at it all of 5 minutes, so perhaps I've missed something. > > > > However, I'm a little surprised you went with a second tree instead of > > doing the top-down thing for data. The way you did it makes it hard to > > have guard pages between text and data. > > I didn't realize the importance of the guard pages. But it is not too I'm not sure how important it is, just seems like a good idea to trap anybody trying to cross that divide. Also, to me it seems like a good idea to have a single large contiguous text region instead of splintered 2M pages. > hard to do it with this approach. For each 2MB text page, we can reserve > 4kB on the beginning and end of it. Would this work? Typically a guard page has different protections (as in none what so ever) so that every access goes *splat*.