linux-kernel - Re: [PATCH v2] makedumpfile: exclude pages that are logically offline

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Message-ID: <7c9d6d5c-d6cf-00a7-7f23-bf28cbb382af@redhat.com>
Date:   Thu, 7 Mar 2019 09:41:15 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Kazuhito Hagio <k-hagio@...jp.nec.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        "xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>,
        kexec-ml <kexec@...ts.infradead.org>,
        "pv-drivers@...are.com" <pv-drivers@...are.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: [PATCH v2] makedumpfile: exclude pages that are logically offline

On 27.11.18 17:32, Kazuhito Hagio wrote:
>> Linux marks pages that are logically offline via a page flag (map count).
>> Such pages e.g. include pages infated as part of a balloon driver or
>> pages that were not actually onlined when onlining the whole section.
>>
>> While the hypervisor usually allows to read such inflated memory, we
>> basically read and dump data that is completely irrelevant. Also, this
>> might result in quite some overhead in the hypervisor. In addition,
>> we saw some problems under Hyper-V, whereby we can crash the kernel by
>> dumping, when reading memory of a partially onlined memory segment
>> (for memory added by the Hyper-V balloon driver).
>>
>> Therefore, don't read and dump pages that are marked as being logically
>> offline.
>>
>> Signed-off-by: David Hildenbrand <david@...hat.com>
> 
> Thanks for the v2 update.
> I'm going to merge this patch after the kernel patches are merged
> and it tests fine with the kernel.
> 
> Kazu

Hi Kazu,

the patches are now upstream. Thanks!

-- 

Thanks,

David / dhildenb