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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 1A7B8C5DF60 for ; Wed, 6 Nov 2019 00:09:18 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 9F598214D8 for ; Wed, 6 Nov 2019 00:09:17 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9F598214D8 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from bilbo.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 4776Mw0tvmzF4vD for ; Wed, 6 Nov 2019 11:09:16 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=intel.com (client-ip=192.55.52.136; helo=mga12.intel.com; envelope-from=sean.j.christopherson@intel.com; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=pass (p=none dis=none) header.from=intel.com Received: from mga12.intel.com (mga12.intel.com [192.55.52.136]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 47757c0xs4zDrZ1 for ; Wed, 6 Nov 2019 10:13:31 +1100 (AEDT) X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by fmsmga106.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 05 Nov 2019 15:13:18 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.68,271,1569308400"; d="scan'208";a="403533470" Received: from sjchrist-coffee.jf.intel.com (HELO linux.intel.com) ([10.54.74.41]) by fmsmga006.fm.intel.com with ESMTP; 05 Nov 2019 15:13:16 -0800 Date: Tue, 5 Nov 2019 15:13:16 -0800 From: Sean Christopherson To: Dan Williams Subject: Re: [PATCH v1 03/10] KVM: Prepare kvm_is_reserved_pfn() for PG_reserved changes Message-ID: <20191105231316.GE23297@linux.intel.com> References: <20191024120938.11237-1-david@redhat.com> <20191024120938.11237-4-david@redhat.com> <01adb4cb-6092-638c-0bab-e61322be7cf5@redhat.com> <613f3606-748b-0e56-a3ad-1efaffa1a67b@redhat.com> <20191105160000.GC8128@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) X-Mailman-Approved-At: Wed, 06 Nov 2019 11:05:37 +1100 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-hyperv@vger.kernel.org, Michal Hocko , Radim =?utf-8?B?S3LEjW3DocWZ?= , KVM list , David Hildenbrand , KarimAllah Ahmed , Dave Hansen , Alexander Duyck , Michal Hocko , Linux MM , Pavel Tatashin , Paul Mackerras , "H. Peter Anvin" , Wanpeng Li , Alexander Duyck , "K. Y. Srinivasan" , Thomas Gleixner , Kees Cook , devel@driverdev.osuosl.org, Stefano Stabellini , Stephen Hemminger , "Aneesh Kumar K.V" , Joerg Roedel , X86 ML , YueHaibing , "Matthew Wilcox \(Oracle\)" , Mike Rapoport , Peter Zijlstra , Ingo Molnar , Vlastimil Babka , Anthony Yznaga , Oscar Salvador , "Isaac J. Manjarres" , Matt Sickler , Juergen Gross , Anshuman Khandual , Haiyang Zhang , Sasha Levin , kvm-ppc@vger.kernel.org, Qian Cai , Alex Williamson , Mike Rapoport , Borislav Petkov , Nicholas Piggin , Andy Lutomirski , xen-devel , Boris Ostrovsky , Vitaly Kuznetsov , Allison Randal , Jim Mattson , Mel Gorman , Adam Borowski , Cornelia Huck , Pavel Tatashin , Linux Kernel Mailing List , Johannes Weiner , Paolo Bonzini , Andrew Morton , linuxppc-dev Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Tue, Nov 05, 2019 at 03:02:40PM -0800, Dan Williams wrote: > On Tue, Nov 5, 2019 at 12:31 PM David Hildenbrand wrote: > > > The scarier code (for me) is transparent_hugepage_adjust() and > > > kvm_mmu_zap_collapsible_spte(), as I don't at all understand the > > > interaction between THP and _PAGE_DEVMAP. > > > > The x86 KVM MMU code is one of the ugliest code I know (sorry, but it > > had to be said :/ ). Luckily, this should be independent of the > > PG_reserved thingy AFAIKs. > > Both transparent_hugepage_adjust() and kvm_mmu_zap_collapsible_spte() > are honoring kvm_is_reserved_pfn(), so again I'm missing where the > page count gets mismanaged and leads to the reported hang. When mapping pages into the guest, KVM gets the page via gup(), which increments the page count for ZONE_DEVICE pages. But KVM puts the page using kvm_release_pfn_clean(), which skips put_page() if PageReserved() and so never puts its reference to ZONE_DEVICE pages. My transparent_hugepage_adjust() and kvm_mmu_zap_collapsible_spte() comments were for a post-patch/series scenario wheren PageReserved() is no longer true for ZONE_DEVICE pages. 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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no 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 6151FC5DF60 for ; Tue, 5 Nov 2019 23:13:49 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 092122084D for ; Tue, 5 Nov 2019 23:13:48 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 092122084D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1iS80y-0007ms-5b; Tue, 05 Nov 2019 23:13:32 +0000 Received: from all-amaz-eas1.inumbo.com ([34.197.232.57] helo=us1-amaz-eas2.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1iS80x-0007mn-1l for xen-devel@lists.xenproject.org; Tue, 05 Nov 2019 23:13:31 +0000 X-Inumbo-ID: e0a42822-0021-11ea-a1a5-12813bfff9fa Received: from mga11.intel.com (unknown [192.55.52.93]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id e0a42822-0021-11ea-a1a5-12813bfff9fa; Tue, 05 Nov 2019 23:13:29 +0000 (UTC) X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by fmsmga102.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 05 Nov 2019 15:13:18 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.68,271,1569308400"; d="scan'208";a="403533470" Received: from sjchrist-coffee.jf.intel.com (HELO linux.intel.com) ([10.54.74.41]) by fmsmga006.fm.intel.com with ESMTP; 05 Nov 2019 15:13:16 -0800 Date: Tue, 5 Nov 2019 15:13:16 -0800 From: Sean Christopherson To: Dan Williams Message-ID: <20191105231316.GE23297@linux.intel.com> References: <20191024120938.11237-1-david@redhat.com> <20191024120938.11237-4-david@redhat.com> <01adb4cb-6092-638c-0bab-e61322be7cf5@redhat.com> <613f3606-748b-0e56-a3ad-1efaffa1a67b@redhat.com> <20191105160000.GC8128@linux.intel.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) Subject: Re: [Xen-devel] [PATCH v1 03/10] KVM: Prepare kvm_is_reserved_pfn() for PG_reserved changes X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: linux-hyperv@vger.kernel.org, Michal Hocko , Radim =?utf-8?B?S3LEjW3DocWZ?= , KVM list , David Hildenbrand , KarimAllah Ahmed , Benjamin Herrenschmidt , Dave Hansen , Alexander Duyck , Michal Hocko , Paul Mackerras , Linux MM , Pavel Tatashin , Paul Mackerras , Michael Ellerman , "H. Peter Anvin" , Wanpeng Li , Alexander Duyck , "K. Y. Srinivasan" , Thomas Gleixner , Kees Cook , devel@driverdev.osuosl.org, Stefano Stabellini , Stephen Hemminger , "Aneesh Kumar K.V" , Joerg Roedel , X86 ML , YueHaibing , "Matthew Wilcox \(Oracle\)" , Mike Rapoport , Peter Zijlstra , Ingo Molnar , Vlastimil Babka , Anthony Yznaga , Oscar Salvador , "Isaac J. Manjarres" , Matt Sickler , Juergen Gross , Anshuman Khandual , Haiyang Zhang , Sasha Levin , kvm-ppc@vger.kernel.org, Qian Cai , Alex Williamson , Mike Rapoport , Borislav Petkov , Nicholas Piggin , Andy Lutomirski , xen-devel , Boris Ostrovsky , Vitaly Kuznetsov , Allison Randal , Jim Mattson , Christophe Leroy , Mel Gorman , Adam Borowski , Cornelia Huck , Pavel Tatashin , Linux Kernel Mailing List , Johannes Weiner , Paolo Bonzini , Andrew Morton , linuxppc-dev Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" T24gVHVlLCBOb3YgMDUsIDIwMTkgYXQgMDM6MDI6NDBQTSAtMDgwMCwgRGFuIFdpbGxpYW1zIHdy b3RlOgo+IE9uIFR1ZSwgTm92IDUsIDIwMTkgYXQgMTI6MzEgUE0gRGF2aWQgSGlsZGVuYnJhbmQg PGRhdmlkQHJlZGhhdC5jb20+IHdyb3RlOgo+ID4gPiBUaGUgc2NhcmllciBjb2RlIChmb3IgbWUp IGlzIHRyYW5zcGFyZW50X2h1Z2VwYWdlX2FkanVzdCgpIGFuZAo+ID4gPiBrdm1fbW11X3phcF9j b2xsYXBzaWJsZV9zcHRlKCksIGFzIEkgZG9uJ3QgYXQgYWxsIHVuZGVyc3RhbmQgdGhlCj4gPiA+ IGludGVyYWN0aW9uIGJldHdlZW4gVEhQIGFuZCBfUEFHRV9ERVZNQVAuCj4gPgo+ID4gVGhlIHg4 NiBLVk0gTU1VIGNvZGUgaXMgb25lIG9mIHRoZSB1Z2xpZXN0IGNvZGUgSSBrbm93IChzb3JyeSwg YnV0IGl0Cj4gPiBoYWQgdG8gYmUgc2FpZCA6LyApLiBMdWNraWx5LCB0aGlzIHNob3VsZCBiZSBp bmRlcGVuZGVudCBvZiB0aGUKPiA+IFBHX3Jlc2VydmVkIHRoaW5neSBBRkFJS3MuCj4gCj4gQm90 aCB0cmFuc3BhcmVudF9odWdlcGFnZV9hZGp1c3QoKSBhbmQga3ZtX21tdV96YXBfY29sbGFwc2li bGVfc3B0ZSgpCj4gYXJlIGhvbm9yaW5nIGt2bV9pc19yZXNlcnZlZF9wZm4oKSwgc28gYWdhaW4g SSdtIG1pc3Npbmcgd2hlcmUgdGhlCj4gcGFnZSBjb3VudCBnZXRzIG1pc21hbmFnZWQgYW5kIGxl YWRzIHRvIHRoZSByZXBvcnRlZCBoYW5nLgoKV2hlbiBtYXBwaW5nIHBhZ2VzIGludG8gdGhlIGd1 ZXN0LCBLVk0gZ2V0cyB0aGUgcGFnZSB2aWEgZ3VwKCksIHdoaWNoCmluY3JlbWVudHMgdGhlIHBh Z2UgY291bnQgZm9yIFpPTkVfREVWSUNFIHBhZ2VzLiAgQnV0IEtWTSBwdXRzIHRoZSBwYWdlCnVz aW5nIGt2bV9yZWxlYXNlX3Bmbl9jbGVhbigpLCB3aGljaCBza2lwcyBwdXRfcGFnZSgpIGlmIFBh Z2VSZXNlcnZlZCgpCmFuZCBzbyBuZXZlciBwdXRzIGl0cyByZWZlcmVuY2UgdG8gWk9ORV9ERVZJ Q0UgcGFnZXMuCgpNeSB0cmFuc3BhcmVudF9odWdlcGFnZV9hZGp1c3QoKSBhbmQga3ZtX21tdV96 YXBfY29sbGFwc2libGVfc3B0ZSgpCmNvbW1lbnRzIHdlcmUgZm9yIGEgcG9zdC1wYXRjaC9zZXJp ZXMgc2NlbmFyaW8gd2hlcmVuIFBhZ2VSZXNlcnZlZCgpIGlzCm5vIGxvbmdlciB0cnVlIGZvciBa T05FX0RFVklDRSBwYWdlcy4KCl9fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19f X19fX19fX19fClhlbi1kZXZlbCBtYWlsaW5nIGxpc3QKWGVuLWRldmVsQGxpc3RzLnhlbnByb2pl Y3Qub3JnCmh0dHBzOi8vbGlzdHMueGVucHJvamVjdC5vcmcvbWFpbG1hbi9saXN0aW5mby94ZW4t ZGV2ZWw= 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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 F0251C5DF61 for ; 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Tue, 5 Nov 2019 23:13:30 +0000 (UTC) X-FDA: 76123777380.22.box20_58b4e6a46b915 X-HE-Tag: box20_58b4e6a46b915 X-Filterd-Recvd-Size: 5418 Received: from mga01.intel.com (mga01.intel.com [192.55.52.88]) by imf41.hostedemail.com (Postfix) with ESMTP for ; Tue, 5 Nov 2019 23:13:29 +0000 (UTC) X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by fmsmga101.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 05 Nov 2019 15:13:18 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.68,271,1569308400"; d="scan'208";a="403533470" Received: from sjchrist-coffee.jf.intel.com (HELO linux.intel.com) ([10.54.74.41]) by fmsmga006.fm.intel.com with ESMTP; 05 Nov 2019 15:13:16 -0800 Date: Tue, 5 Nov 2019 15:13:16 -0800 From: Sean Christopherson To: Dan Williams Cc: David Hildenbrand , 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 , Radim =?utf-8?B?S3LEjW3DocWZ?= , Sasha Levin , Stefano Stabellini , Stephen Hemminger , Thomas Gleixner , Vitaly Kuznetsov , Vlastimil Babka , Wanpeng Li , YueHaibing , Adam Borowski Subject: Re: [PATCH v1 03/10] KVM: Prepare kvm_is_reserved_pfn() for PG_reserved changes Message-ID: <20191105231316.GE23297@linux.intel.com> References: <20191024120938.11237-1-david@redhat.com> <20191024120938.11237-4-david@redhat.com> <01adb4cb-6092-638c-0bab-e61322be7cf5@redhat.com> <613f3606-748b-0e56-a3ad-1efaffa1a67b@redhat.com> <20191105160000.GC8128@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) 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 Tue, Nov 05, 2019 at 03:02:40PM -0800, Dan Williams wrote: > On Tue, Nov 5, 2019 at 12:31 PM David Hildenbrand wrote: > > > The scarier code (for me) is transparent_hugepage_adjust() and > > > kvm_mmu_zap_collapsible_spte(), as I don't at all understand the > > > interaction between THP and _PAGE_DEVMAP. > > > > The x86 KVM MMU code is one of the ugliest code I know (sorry, but it > > had to be said :/ ). Luckily, this should be independent of the > > PG_reserved thingy AFAIKs. > > Both transparent_hugepage_adjust() and kvm_mmu_zap_collapsible_spte() > are honoring kvm_is_reserved_pfn(), so again I'm missing where the > page count gets mismanaged and leads to the reported hang. When mapping pages into the guest, KVM gets the page via gup(), which increments the page count for ZONE_DEVICE pages. But KVM puts the page using kvm_release_pfn_clean(), which skips put_page() if PageReserved() and so never puts its reference to ZONE_DEVICE pages. My transparent_hugepage_adjust() and kvm_mmu_zap_collapsible_spte() comments were for a post-patch/series scenario wheren PageReserved() is no longer true for ZONE_DEVICE pages.