Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751508AbaFEL4R (ORCPT ); Thu, 5 Jun 2014 07:56:17 -0400 Received: from cantor2.suse.de ([195.135.220.15]:58475 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750864AbaFEL4Q (ORCPT ); Thu, 5 Jun 2014 07:56:16 -0400 Message-ID: <53905ADB.8000100@suse.de> Date: Thu, 05 Jun 2014 13:56:11 +0200 From: Alexander Graf User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:24.0) Gecko/20100101 Thunderbird/24.5.0 MIME-Version: 1.0 To: Benjamin Herrenschmidt , Alexey Kardashevskiy CC: linuxppc-dev@lists.ozlabs.org, Paul Mackerras , Gleb Natapov , Paolo Bonzini , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, kvm-ppc@vger.kernel.org Subject: Re: [PATCH 3/3] PPC: KVM: Add support for 64bit TCE windows References: <1401953144-19186-1-git-send-email-aik@ozlabs.ru> <1401953144-19186-4-git-send-email-aik@ozlabs.ru> <1401953908.3247.121.camel@pasglop> <539037DB.5080706@ozlabs.ru> <1401964037.3247.129.camel@pasglop> In-Reply-To: <1401964037.3247.129.camel@pasglop> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05.06.14 12:27, Benjamin Herrenschmidt wrote: > On Thu, 2014-06-05 at 19:26 +1000, Alexey Kardashevskiy wrote: >> No trees yet. For 64GB window we need (64<<30)/(16<<20)*8 = 32K TCE table. >> Do we really need trees? > The above is assuming hugetlbfs backed guests. These are the least of my worry > indeed. But we need to deal with 4k and 64k guests. What if we ask user space to give us a pointer to user space allocated memory along with the TCE registration? We would still ask user space to only use the returned fd for TCE modifications, but would have some nicely swappable memory we can store the TCE entries in. In fact, the code as is today can allocate an arbitrary amount of pinned kernel memory from within user space without any checks. Alex -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/