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 X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 607D5C43144 for ; Mon, 25 Jun 2018 11:08:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1F0D020779 for ; Mon, 25 Jun 2018 11:08:36 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1F0D020779 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932361AbeFYLId (ORCPT ); Mon, 25 Jun 2018 07:08:33 -0400 Received: from mx2.suse.de ([195.135.220.15]:36551 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932089AbeFYLIc (ORCPT ); Mon, 25 Jun 2018 07:08:32 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay1.suse.de (charybdis-ext-too.suse.de [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 41FABAD52; Mon, 25 Jun 2018 11:08:31 +0000 (UTC) Date: Mon, 25 Jun 2018 13:08:30 +0200 From: Michal Hocko To: Paolo Bonzini Cc: LKML , kvm@vger.kernel.org, Radim =?utf-8?B?S3LEjW3DocWZ?= , linux-mm@kvack.org, Andrea Arcangeli , =?iso-8859-1?B?Suly9G1l?= Glisse Subject: Re: [RFC PATCH] mm, oom: distinguish blockable mode for mmu notifiers Message-ID: <20180625110830.GJ28965@dhcp22.suse.cz> References: <20180622150242.16558-1-mhocko@kernel.org> <20180625075715.GA28965@dhcp22.suse.cz> <20180625084529.GC28965@dhcp22.suse.cz> <45e1a12c-280b-635a-fc76-716440f084ec@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <45e1a12c-280b-635a-fc76-716440f084ec@redhat.com> User-Agent: Mutt/1.9.5 (2018-04-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon 25-06-18 12:34:43, Paolo Bonzini wrote: > On 25/06/2018 10:45, Michal Hocko wrote: > > On Mon 25-06-18 10:10:18, Paolo Bonzini wrote: > >> On 25/06/2018 09:57, Michal Hocko wrote: > >>> On Sun 24-06-18 10:11:21, Paolo Bonzini wrote: > >>>> On 22/06/2018 17:02, Michal Hocko wrote: > >>>>> @@ -7215,6 +7216,8 @@ void kvm_arch_mmu_notifier_invalidate_range(struct kvm *kvm, > >>>>> apic_address = gfn_to_hva(kvm, APIC_DEFAULT_PHYS_BASE >> PAGE_SHIFT); > >>>>> if (start <= apic_address && apic_address < end) > >>>>> kvm_make_all_cpus_request(kvm, KVM_REQ_APIC_PAGE_RELOAD); > >>>>> + > >>>>> + return 0; > >>>> > >>>> This is wrong, gfn_to_hva can sleep. > >>> > >>> Hmm, I have tried to crawl the call chain and haven't found any > >>> sleepable locks taken. Maybe I am just missing something. > >>> __kvm_memslots has a complex locking assert. I do not see we would take > >>> slots_lock anywhere from the notifier call path. IIUC that means that > >>> users_count has to be zero at that time. I have no idea how that is > >>> guaranteed. > >> > >> Nevermind, ENOCOFFEE. This is gfn_to_hva, not gfn_to_pfn. It only > >> needs SRCU. > > > > OK, so just the make sure I follow, the change above is correct? > > Yes. It's only gfn_to_pfn that calls get_user_pages and therefore can > sleep. OK, thanks for the confirmation! -- Michal Hocko SUSE Labs