From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wg0-f49.google.com (mail-wg0-f49.google.com [74.125.82.49]) by kanga.kvack.org (Postfix) with ESMTP id 2B24B6B0069 for ; Tue, 21 Oct 2014 02:11:44 -0400 (EDT) Received: by mail-wg0-f49.google.com with SMTP id x12so484854wgg.32 for ; Mon, 20 Oct 2014 23:11:43 -0700 (PDT) Received: from e06smtp14.uk.ibm.com (e06smtp14.uk.ibm.com. [195.75.94.110]) by mx.google.com with ESMTPS id q9si10923159wiz.17.2014.10.20.23.11.42 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Mon, 20 Oct 2014 23:11:42 -0700 (PDT) Received: from /spool/local by e06smtp14.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 21 Oct 2014 07:11:41 +0100 Received: from b06cxnps4074.portsmouth.uk.ibm.com (d06relay11.portsmouth.uk.ibm.com [9.149.109.196]) by d06dlp03.portsmouth.uk.ibm.com (Postfix) with ESMTP id 7055A1B08023 for ; Tue, 21 Oct 2014 07:11:38 +0100 (BST) Received: from d06av03.portsmouth.uk.ibm.com (d06av03.portsmouth.uk.ibm.com [9.149.37.213]) by b06cxnps4074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id s9L6BcbF15401406 for ; Tue, 21 Oct 2014 06:11:38 GMT Received: from d06av03.portsmouth.uk.ibm.com (localhost [127.0.0.1]) by d06av03.portsmouth.uk.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id s9L6BZkg013845 for ; Tue, 21 Oct 2014 00:11:38 -0600 Date: Tue, 21 Oct 2014 08:11:31 +0200 From: Martin Schwidefsky Subject: Re: [PATCH 2/4] mm: introduce new VM_NOZEROPAGE flag Message-ID: <20141021081131.641c6104@mschwide> In-Reply-To: <5445511D.1090603@redhat.com> References: <1413554990-48512-1-git-send-email-dingel@linux.vnet.ibm.com> <1413554990-48512-3-git-send-email-dingel@linux.vnet.ibm.com> <54419265.9000000@intel.com> <20141018164928.2341415f@BR9TG4T3.de.ibm.com> <54429521.80402@intel.com> <5445511D.1090603@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Paolo Bonzini Cc: Dave Hansen , Dominik Dingel , Andrew Morton , linux-mm@kvack.org, Mel Gorman , Michal Hocko , Rik van Riel , Andrea Arcangeli , Andy Lutomirski , "Aneesh Kumar K.V" , Bob Liu , Christian Borntraeger , Cornelia Huck , Gleb Natapov , Heiko Carstens , "H. Peter Anvin" , Hugh Dickins , Ingo Molnar , Jianyu Zhan , Johannes Weiner , "Kirill A. Shutemov" , Konstantin Weitz , kvm@vger.kernel.org, linux390@de.ibm.com, linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, Peter Zijlstra , Sasha Levin On Mon, 20 Oct 2014 20:14:53 +0200 Paolo Bonzini wrote: > On 10/18/2014 06:28 PM, Dave Hansen wrote: > > > Currently it is an all or nothing thing, but for a future change we might want to just > > > tag the guest memory instead of the complete user address space. > > > > I think it's a bad idea to reserve a flag for potential future use. If > > you_need_ it in the future, let's have the discussion then. For now, I > > think it should probably just be stored in the mm somewhere. > > I agree with Dave (I thought I disagreed, but I changed my mind while > writing down my thoughts). Just define mm_forbids_zeropage in > arch/s390/include/asm, and make it return mm->context.use_skey---with a > comment explaining how this is only for processes that use KVM, and then > only for guests that use storage keys. The mm_forbids_zeropage() sure will work for now, but I think a vma flag is the better solution. This is analog to VM_MERGEABLE or VM_NOHUGEPAGE, the best solution would be to only mark those vmas that are mapped to the guest. That we have not found a way to do that yet in a sensible way does not change the fact that "no-zero-page" is a per-vma property, no? But if you insist we go with the mm_forbids_zeropage() until we find a clever way to distinguish the guest vmas from the qemu ones. -- blue skies, Martin. "Reality continues to ruin my life." - Calvin. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org