From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Hansen Subject: Re: [PATCH v7 03/14] x86/cet/ibt: Add IBT legacy code bitmap setup function Date: Mon, 10 Jun 2019 15:02:45 -0700 Message-ID: <92e56b28-0cd4-e3f4-867b-639d9b98b86c@intel.com> References: <20190606200926.4029-1-yu-cheng.yu@intel.com> <20190606200926.4029-4-yu-cheng.yu@intel.com> <20190607080832.GT3419@hirez.programming.kicks-ass.net> <20190607174336.GM3436@hirez.programming.kicks-ass.net> <34E0D316-552A-401C-ABAA-5584B5BC98C5@amacapital.net> <7e0b97bf1fbe6ff20653a8e4e147c6285cc5552d.camel@intel.com> <25281DB3-FCE4-40C2-BADB-B3B05C5F8DD3@amacapital.net> <3f19582d-78b1-5849-ffd0-53e8ca747c0d@intel.com> <5aa98999b1343f34828414b74261201886ec4591.camel@intel.com> <0665416d-9999-b394-df17-f2a5e1408130@intel.com> <5c8727dde9653402eea97bfdd030c479d1e8dd99.camel@intel.com> <328275c9b43c06809c9937c83d25126a6e3efcbd.camel@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <328275c9b43c06809c9937c83d25126a6e3efcbd.camel@intel.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Yu-cheng Yu , Andy Lutomirski Cc: Peter Zijlstra , x86@kernel.org, "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-api@vger.kernel.org, Arnd Bergmann , Balbir Singh , Borislav Petkov , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H.J. Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit List-Id: linux-arch.vger.kernel.org On 6/10/19 1:58 PM, Yu-cheng Yu wrote: >>> On each memory request, the kernel then must consider a percentage of >>> allocated space in its calculation, and on systems with less memory >>> this quickly becomes a problem. >> I'm not sure what you're referring to here? Are you referring to our >> overcommit limits? > Yes. My assumption has always been that these large, potentially sparse hardware tables *must* be mmap()'d with MAP_NORESERVE specified. That should keep them from being problematic with respect to overcommit. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga11.intel.com ([192.55.52.93]:63430 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728651AbfFJWCs (ORCPT ); Mon, 10 Jun 2019 18:02:48 -0400 Subject: Re: [PATCH v7 03/14] x86/cet/ibt: Add IBT legacy code bitmap setup function References: <20190606200926.4029-1-yu-cheng.yu@intel.com> <20190606200926.4029-4-yu-cheng.yu@intel.com> <20190607080832.GT3419@hirez.programming.kicks-ass.net> <20190607174336.GM3436@hirez.programming.kicks-ass.net> <34E0D316-552A-401C-ABAA-5584B5BC98C5@amacapital.net> <7e0b97bf1fbe6ff20653a8e4e147c6285cc5552d.camel@intel.com> <25281DB3-FCE4-40C2-BADB-B3B05C5F8DD3@amacapital.net> <3f19582d-78b1-5849-ffd0-53e8ca747c0d@intel.com> <5aa98999b1343f34828414b74261201886ec4591.camel@intel.com> <0665416d-9999-b394-df17-f2a5e1408130@intel.com> <5c8727dde9653402eea97bfdd030c479d1e8dd99.camel@intel.com> <328275c9b43c06809c9937c83d25126a6e3efcbd.camel@intel.com> From: Dave Hansen Message-ID: <92e56b28-0cd4-e3f4-867b-639d9b98b86c@intel.com> Date: Mon, 10 Jun 2019 15:02:45 -0700 MIME-Version: 1.0 In-Reply-To: <328275c9b43c06809c9937c83d25126a6e3efcbd.camel@intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-arch-owner@vger.kernel.org List-ID: To: Yu-cheng Yu , Andy Lutomirski Cc: Peter Zijlstra , x86@kernel.org, "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-api@vger.kernel.org, Arnd Bergmann , Balbir Singh , Borislav Petkov , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H.J. Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Randy Dunlap , "Ravi V. Shankar" , Vedvyas Shanbhogue , Dave Martin Message-ID: <20190610220245.MZdA_1ntvILeyuOYD8DvdIzd-2N0XuZRslBEcyGgOcM@z> On 6/10/19 1:58 PM, Yu-cheng Yu wrote: >>> On each memory request, the kernel then must consider a percentage of >>> allocated space in its calculation, and on systems with less memory >>> this quickly becomes a problem. >> I'm not sure what you're referring to here? Are you referring to our >> overcommit limits? > Yes. My assumption has always been that these large, potentially sparse hardware tables *must* be mmap()'d with MAP_NORESERVE specified. That should keep them from being problematic with respect to overcommit.