From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexander Graf Subject: Re: [PATCH -V3 2/4] powerpc/kvm: Contiguous memory allocator based hash page table allocation Date: Tue, 02 Jul 2013 17:32:57 +0200 Message-ID: <51D2F2A9.8040503@suse.de> References: <1372743918-12293-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <1372743918-12293-2-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <51D2EDD7.9060205@suse.de> <87wqp9yo4m.fsf@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: benh@kernel.crashing.org, paulus@samba.org, m.szyprowski@samsung.com, mina86@mina86.com, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, kvm-ppc@vger.kernel.org, kvm@vger.kernel.org To: "Aneesh Kumar K.V" Return-path: Received: from cantor2.suse.de ([195.135.220.15]:52794 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753760Ab3GBPdB (ORCPT ); Tue, 2 Jul 2013 11:33:01 -0400 In-Reply-To: <87wqp9yo4m.fsf@linux.vnet.ibm.com> Sender: kvm-owner@vger.kernel.org List-ID: On 07/02/2013 05:31 PM, Aneesh Kumar K.V wrote: > Alexander Graf writes: > >> On 07/02/2013 07:45 AM, Aneesh Kumar K.V wrote: >>> From: "Aneesh Kumar K.V" >>> >>> Powerpc architecture uses a hash based page table mechanism for mapping virtual >>> addresses to physical address. The architecture require this hash page table to >>> be physically contiguous. With KVM on Powerpc currently we use early reservation >>> mechanism for allocating guest hash page table. This implies that we need to >>> reserve a big memory region to ensure we can create large number of guest >>> simultaneously with KVM on Power. Another disadvantage is that the reserved memory >>> is not available to rest of the subsystems and and that implies we limit the total >>> available memory in the host. >>> >>> This patch series switch the guest hash page table allocation to use >>> contiguous memory allocator. >>> >>> Signed-off-by: Aneesh Kumar K.V >> Is CMA a mandatory option in the kernel? Or can it be optionally >> disabled? If it can be disabled, we should keep the preallocated >> fallback case around for systems that have CMA disabled. >> > CMA is not a mandatory option. But we have > > config KVM_BOOK3S_64_HV > bool "KVM support for POWER7 and PPC970 using hypervisor mode in host" > depends on KVM_BOOK3S_64 > select MMU_NOTIFIER > select CMA > > ie, for book3s HV we select CMA and only this CMA needs is memblock > which we already support Ah, that was the hunk I did miss. Thanks a lot, then it's perfectly fine of course :). Very nice patch set btw. Alex