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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: <57d8a558-dcb3-b318-8e38-6c016b050414@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 24.06.20 09:48, David Hildenbrand wrote: > On 23.06.20 17:18, Michal Hocko wrote: >> On Tue 23-06-20 17:42:58, Wei Yang wrote: >>> For early sections, we assumes its memmap will never be partially >>> removed. But current behavior breaks this. >>> >>> Let's correct it. >>> >>> Fixes: ba72b4c8cf60 ("mm/sparsemem: support sub-section hotplug") >>> Signed-off-by: Wei Yang >> >> Can a user trigger this or is this a theoretical bug? > > I tried to reproduce it, but somehow I get unexpected behavior. > With a hacked QEMU I can get > > $ cat /proc/iomem > [...] > 100000000-143ffffff : System RAM > 144000000-343dfffff : Persistent Memory > 144000000-1441fffff : namespace0.0 > 144200000-144ffffff : dax0.0 > > After > $ ndctl create-namespace --force --reconfig=namespace0.0 --mode=devdax --size=16M > > I get > > $ cat /proc/iomem > [...] > 100000000-143ffffff : System RAM > 144000000-343dfffff : Persistent Memory > 144000000-1441fffff : namespace0.0 > 144200000-144ffffff : dax0.0 > > I can trigger remove+re-add via > $ ndctl create-namespace --force --reconfig=namespace0.0 --mode=devdax --size=16M > > So we clearly have an overlap between System RAM and dax0.0 within a section. > However, I never get early_section() to trigger in > section_activate()/section_deactivate() ? That's unexpected ... booting the correct kernel I can see the printk's I added ... I'll continue to poke it with a stick. -- Thanks, David / dhildenb