linux-kernel - Re: remove Xen tmem leftovers

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Message-ID: <93a8e489-5ca5-7593-5d2b-59280187e2a1@redhat.com>
Date:   Wed, 5 Jan 2022 09:46:05 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Juergen Gross <jgross@...e.com>, Christoph Hellwig <hch@....de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc:     Hugh Dickins <hughd@...gle.com>,
        Seth Jennings <sjenning@...hat.com>,
        Dan Streetman <ddstreet@...e.org>,
        Vitaly Wool <vitaly.wool@...sulko.com>,
        Matthew Wilcox <willy@...radead.org>,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: remove Xen tmem leftovers

On 05.01.22 07:08, Juergen Gross wrote:
> On 04.01.22 15:31, David Hildenbrand wrote:
>> On 24.12.21 07:22, Christoph Hellwig wrote:
>>> Hi all,
>>>
>>> since the remove of the Xen tmem driver in 2019, the cleancache hooks are
>>> entirely unused, as are large parts of frontswap.  This series against
>>> linux-next (with the folio changes included) removes cleancaches, and cuts
>>> down frontswap to the bits actually used by zswap.
>>>
>>
>> Just out of curiosity, why was tmem removed from Linux (or even Xen?).
>> Do you have any information?
> 
> tmem never made it past the "experimental" state in the Xen hypervisor.
> Its implementation had some significant security flaws, there was no
> maintainer left, and nobody stepped up to address those issues.
> 
> As a result tmem was removed from Xen.

Interesting, thanks for sharing. I know tmem mostly from the papers and
thought it was an interesting approach in general. There was even papers
about a virtio implementation, however, actual code never appeared in
the wild :)

-- 
Thanks,

David / dhildenb