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[79.242.59.179]) by smtp.gmail.com with ESMTPSA id q5sm4533504wmc.0.2021.07.15.02.42.21 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 15 Jul 2021 02:42:23 -0700 (PDT) To: Heiko Carstens , Andrew Morton Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Vitaly Kuznetsov , "Michael S. Tsirkin" , Jason Wang , Pankaj Gupta , Wei Yang , Oscar Salvador , Michal Hocko , Dan Williams , Anshuman Khandual , Dave Hansen , Vlastimil Babka , Mike Rapoport , "Rafael J. Wysocki" , Len Brown , Pavel Tatashin , Michael Ellerman , Catalin Marinas , virtualization@lists.linux-foundation.org, linux-acpi@vger.kernel.org, Andy Lutomirski , "Aneesh Kumar K.V" , Anton Blanchard , Ard Biesheuvel , Baoquan He , Benjamin Herrenschmidt , Borislav Petkov , Christian Borntraeger , Christophe Leroy , Dave Jiang , "H. Peter Anvin" , Ingo Molnar , Jia He , Joe Perches , Kefeng Wang , Laurent Dufour , Michel Lespinasse , Nathan Lynch , Nicholas Piggin , Paul Mackerras , Peter Zijlstra , Pierre Morel , "Rafael J. Wysocki" , Rich Felker , Scott Cheloha , Sergei Trofimovich , Thiago Jung Bauermann , Thomas Gleixner , Vasily Gorbik , Vishal Verma , Will Deacon , Yoshinori Sato References: <20210712124052.26491-1-david@redhat.com> <20210712124052.26491-2-david@redhat.com> From: David Hildenbrand Organization: Red Hat Subject: Re: [PATCH v1 1/4] mm/memory_hotplug: use "unsigned long" for PFN in zone_for_pfn_range() Message-ID: <99c59db8-4c3d-6bee-9acc-41a8f76899ef@redhat.com> Date: Thu, 15 Jul 2021 11:42:21 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Authentication-Results: imf05.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=Dae2hoIu; spf=none (imf05.hostedemail.com: domain of david@redhat.com has no SPF policy when checking 216.205.24.124) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=none) header.from=redhat.com X-Rspamd-Server: rspam02 X-Stat-Signature: 1haeay9unw3ie4cj4pq61uqm19enznfz X-Rspamd-Queue-Id: 84A74500D717 X-HE-Tag: 1626342150-658759 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 14.07.21 22:13, Heiko Carstens wrote: > On Mon, Jul 12, 2021 at 02:40:49PM +0200, David Hildenbrand wrote: >> Checkpatch complained on a follow-up patch that we are using "unsigned= " >> here, which defaults to "unsigned int" and checkpatch is correct. >> >> Use "unsigned long" instead, just as we do in other places when handli= ng >> PFNs. This can bite us once we have physical addresses in the range of >> multiple TB. >> >> Fixes: e5e689302633 ("mm, memory_hotplug: display allowed zones in the= preferred ordering") >> Signed-off-by: David Hildenbrand >> --- >> include/linux/memory_hotplug.h | 4 ++-- >> mm/memory_hotplug.c | 4 ++-- >> 2 files changed, 4 insertions(+), 4 deletions(-) >=20 > I'd propose to add Cc: since I actually had > the fun to try to debug something like this a couple of years ago: > 6cdb18ad98a4 ("mm/vmstat: fix overflow in mod_zone_page_state()") >=20 Good point, and thinking again what can go wrong, I tend to agree. We=20 are trying to keep zones contiguous and it could happen that we end up=20 with something like ZONE_DMA here (via default_kernel_zone_for_pfn())=20 and would consequently online something to ZONE_DMA that doesn't belong=20 there, resulting in crashes. @Andrew can you add Cc: and "As we will search for a fitting zone using the wrong pfn, we might end=20 up onlining memory to one of the special kernel zones, such as ZONE_DMA,=20 which can end badly as the onlined memory does not satisfy properties of=20 these zones." Thanks Heiko! --=20 Thanks, David / dhildenb