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=-6.7 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 B911BCA9EC7 for ; Tue, 5 Nov 2019 04:39:10 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 44B88217F4 for ; Tue, 5 Nov 2019 04:39:10 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=intel-com.20150623.gappssmtp.com header.i=@intel-com.20150623.gappssmtp.com header.b="yhHHwHps" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 44B88217F4 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id A2DCB6B0003; Mon, 4 Nov 2019 23:39:09 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 9B7C76B0006; Mon, 4 Nov 2019 23:39:09 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 87F136B0007; Mon, 4 Nov 2019 23:39:09 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0107.hostedemail.com [216.40.44.107]) by kanga.kvack.org (Postfix) with ESMTP id 7090A6B0003 for ; Mon, 4 Nov 2019 23:39:09 -0500 (EST) Received: from smtpin10.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with SMTP id 0B21E2DFC for ; Tue, 5 Nov 2019 04:39:09 +0000 (UTC) X-FDA: 76120969218.10.smoke79_6ce005e772b21 X-HE-Tag: smoke79_6ce005e772b21 X-Filterd-Recvd-Size: 7422 Received: from mail-ot1-f66.google.com (mail-ot1-f66.google.com [209.85.210.66]) by imf42.hostedemail.com (Postfix) with ESMTP for ; Tue, 5 Nov 2019 04:39:08 +0000 (UTC) Received: by mail-ot1-f66.google.com with SMTP id v24so11235822otp.5 for ; Mon, 04 Nov 2019 20:39:07 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=intel-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=LQ/3CY3Z/pwD7vktjhd0l5Hf+cHLJkYRKb4mMFAX40w=; b=yhHHwHpstkv84TevZIhs/Wm18KmjQCTMD7QlgnCZ3d31OxhoY6s6I3rfk8ud7Ml9XW NzkBxxxgjNUnDFVFhwgBwUgJux1TVnbKP5vdJwRFwQ+/giMyREG6ohSNQy9TeoSZJP8T SPIO/dUqQUV+56+4q+tqGSp5zgkTlc1mY6zJa37wVenBzWpatnn2O1AzlEI006uGn0Ia +fAj7hOgp2UmAGxqae4eaNY8IDMTTdkrkZFK6SjUqy87+8sumJ4XhFeiC35vbDkoayxx uGfCGRfgl5zfXbcSzaVw9hv/WN8gLBd6EeLAtnBu48QoPLD4qlg6djtdWgKDg7cH2aI4 CIaQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=LQ/3CY3Z/pwD7vktjhd0l5Hf+cHLJkYRKb4mMFAX40w=; b=VLzozxPBvnOjpXSS75uuxAu6lVLBLSTQM1qnQoW/2keUdwYoybVjNY1IVKU9xb6yKr +iWoferOkurPtSjun1890+usdJSDpxr1Nf189drs3v0kFKBCZ1+gH+86VMmgEmmsuWYw iFOMsskH9K52MJFMUsA+WRL+e3x81LeK8zENKgmNC4Eg54ggEZTWCK2VbLpIIpK2xWot mzsKqmkDr85mwUZX0zZ1gcq7x+k+OP31FnyHRA5emdbGSEigkczLOtalTiLjHop9FIwU S1Dij3SUQJapAB6aYhOcL2j5TPbUQRwql/yPVwgmbD4FnvJ3rTvrXRh8JtBej4FKnlR4 AkbQ== X-Gm-Message-State: APjAAAXPYooLqupCDhMxk1P4oyeG1fERtHOmv67g5pmbpbqXpP74h+B0 tf/5IHklVGk0vc4CwDl1hN/gQd2T12hPYQdzTT9epA== X-Google-Smtp-Source: APXvYqw5MaEjuPSBWubL0ieUUp4Y5rryBa4JzAq8q4R6lrgIw09Afe+NdZFy6gkARWQQx7v95Lg8Rh1zBTQaSC9BU+U= X-Received: by 2002:a9d:30c8:: with SMTP id r8mr3863066otg.363.1572928747302; Mon, 04 Nov 2019 20:39:07 -0800 (PST) MIME-Version: 1.0 References: <20191024120938.11237-1-david@redhat.com> <20191024120938.11237-4-david@redhat.com> In-Reply-To: <20191024120938.11237-4-david@redhat.com> From: Dan Williams Date: Mon, 4 Nov 2019 20:38:56 -0800 Message-ID: Subject: Re: [PATCH v1 03/10] KVM: Prepare kvm_is_reserved_pfn() for PG_reserved changes To: David Hildenbrand Cc: Linux Kernel Mailing List , Linux MM , Michal Hocko , Andrew Morton , kvm-ppc@vger.kernel.org, linuxppc-dev , KVM list , linux-hyperv@vger.kernel.org, devel@driverdev.osuosl.org, xen-devel , X86 ML , Alexander Duyck , Alexander Duyck , Alex Williamson , Allison Randal , Andy Lutomirski , "Aneesh Kumar K.V" , Anshuman Khandual , Anthony Yznaga , Benjamin Herrenschmidt , Borislav Petkov , Boris Ostrovsky , Christophe Leroy , Cornelia Huck , Dave Hansen , Haiyang Zhang , "H. Peter Anvin" , Ingo Molnar , "Isaac J. Manjarres" , Jim Mattson , Joerg Roedel , Johannes Weiner , Juergen Gross , KarimAllah Ahmed , Kees Cook , "K. Y. Srinivasan" , "Matthew Wilcox (Oracle)" , Matt Sickler , Mel Gorman , Michael Ellerman , Michal Hocko , Mike Rapoport , Mike Rapoport , Nicholas Piggin , Oscar Salvador , Paolo Bonzini , Paul Mackerras , Paul Mackerras , Pavel Tatashin , Pavel Tatashin , Peter Zijlstra , Qian Cai , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Sasha Levin , Sean Christopherson , Stefano Stabellini , Stephen Hemminger , Thomas Gleixner , Vitaly Kuznetsov , Vlastimil Babka , Wanpeng Li , YueHaibing , Adam Borowski Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Oct 24, 2019 at 5:11 AM David Hildenbrand wrote: > > Right now, ZONE_DEVICE memory is always set PG_reserved. We want to > change that. > > KVM has this weird use case that you can map anything from /dev/mem > into the guest. pfn_valid() is not a reliable check whether the memmap > was initialized and can be touched. pfn_to_online_page() makes sure > that we have an initialized memmap (and don't have ZONE_DEVICE memory). > > Rewrite kvm_is_reserved_pfn() to make sure the function produces the > same result once we stop setting ZONE_DEVICE pages PG_reserved. > > Cc: Paolo Bonzini > Cc: "Radim Kr=C4=8Dm=C3=A1=C5=99" > Cc: Michal Hocko > Cc: Dan Williams > Cc: KarimAllah Ahmed > Signed-off-by: David Hildenbrand > --- > virt/kvm/kvm_main.c | 10 ++++++++-- > 1 file changed, 8 insertions(+), 2 deletions(-) > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index e9eb666eb6e8..9d18cc67d124 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -151,9 +151,15 @@ __weak int kvm_arch_mmu_notifier_invalidate_range(st= ruct kvm *kvm, > > bool kvm_is_reserved_pfn(kvm_pfn_t pfn) > { > - if (pfn_valid(pfn)) > - return PageReserved(pfn_to_page(pfn)); > + struct page *page =3D pfn_to_online_page(pfn); > > + /* > + * We treat any pages that are not online (not managed by the bud= dy) > + * as reserved - this includes ZONE_DEVICE pages and pages withou= t > + * a memmap (e.g., mapped via /dev/mem). > + */ > + if (page) > + return PageReserved(page); > return true; > } So after this all the pfn_valid() usage in kvm_main.c is replaced with pfn_to_online_page()? Looks correct to me. However, I'm worried that kvm is taking reference on ZONE_DEVICE pages through some other path resulting in this: https://lore.kernel.org/linux-nvdimm/20190919154708.GA24650@angband.pl/ I'll see if this patch set modulates or maintains that failure mode.