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Subject: Re: [PATCH v1 5/7] mm: introduce
 page_offline_(begin|end|freeze|unfreeze) to synchronize setting PageOffline()
To:     Mike Rapoport <rppt@kernel.org>
Cc:     linux-kernel@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>,
        "Michael S. Tsirkin" <mst@redhat.com>,
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        Alex Shi <alex.shi@linux.alibaba.com>,
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        Mike Kravetz <mike.kravetz@oracle.com>,
        Aili Yao <yaoaili@kingsoft.com>, Jiri Bohac <jbohac@suse.cz>,
        "K. Y. Srinivasan" <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        Stephen Hemminger <sthemmin@microsoft.com>,
        Wei Liu <wei.liu@kernel.org>,
        Naoya Horiguchi <naoya.horiguchi@nec.com>,
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References: <20210429122519.15183-1-david@redhat.com>
 <20210429122519.15183-6-david@redhat.com> <YI5Hp49AmWgfTzNy@kernel.org>
From:   David Hildenbrand <david@redhat.com>
Organization: Red Hat
Message-ID: <4aa55978-c224-7ead-f00d-df1a6c3dfda4@redhat.com>
Date:   Mon, 3 May 2021 10:11:29 +0200
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On 02.05.21 08:33, Mike Rapoport wrote:
> On Thu, Apr 29, 2021 at 02:25:17PM +0200, David Hildenbrand wrote:
>> A driver might set a page logically offline -- PageOffline() -- and
>> turn the page inaccessible in the hypervisor; after that, access to page
>> content can be fatal. One example is virtio-mem; while unplugged memory
>> -- marked as PageOffline() can currently be read in the hypervisor, this
>> will no longer be the case in the future; for example, when having
>> a virtio-mem device backed by huge pages in the hypervisor.
>>
>> Some special PFN walkers -- i.e., /proc/kcore -- read content of random
>> pages after checking PageOffline(); however, these PFN walkers can race
>> with drivers that set PageOffline().
>>
>> Let's introduce page_offline_(begin|end|freeze|unfreeze) for
> 
> Bikeshed: freeze|thaw?
>

Sure :)


-- 
Thanks,

David / dhildenb