linux-kernel - Re: [PATCH 02/16] mm: introduce leaf entry type and use to simplify leaf entry logic

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <f8f748ca-3bf0-473d-bd91-ca2bb1141511@lucifer.local>
Date: Wed, 5 Nov 2025 19:56:10 +0000
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Matthew Wilcox <willy@...radead.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        David Hildenbrand <david@...hat.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Gerald Schaefer <gerald.schaefer@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>, Peter Xu <peterx@...hat.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>,
        Arnd Bergmann <arnd@...db.de>, Zi Yan <ziy@...dia.com>,
        Baolin Wang <baolin.wang@...ux.alibaba.com>,
        "Liam R . Howlett" <Liam.Howlett@...cle.com>,
        Nico Pache <npache@...hat.com>, Ryan Roberts <ryan.roberts@....com>,
        Dev Jain <dev.jain@....com>, Barry Song <baohua@...nel.org>,
        Lance Yang <lance.yang@...ux.dev>, Muchun Song <muchun.song@...ux.dev>,
        Oscar Salvador <osalvador@...e.de>, Vlastimil Babka <vbabka@...e.cz>,
        Mike Rapoport <rppt@...nel.org>,
        Suren Baghdasaryan <surenb@...gle.com>, Michal Hocko <mhocko@...e.com>,
        Matthew Brost <matthew.brost@...el.com>,
        Joshua Hahn <joshua.hahnjy@...il.com>, Rakie Kim <rakie.kim@...com>,
        Byungchul Park <byungchul@...com>, Gregory Price <gourry@...rry.net>,
        Ying Huang <ying.huang@...ux.alibaba.com>,
        Alistair Popple <apopple@...dia.com>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        Yuanchu Xie <yuanchu@...gle.com>, Wei Xu <weixugc@...gle.com>,
        Kemeng Shi <shikemeng@...weicloud.com>,
        Kairui Song <kasong@...cent.com>, Nhat Pham <nphamcs@...il.com>,
        Baoquan He <bhe@...hat.com>, Chris Li <chrisl@...nel.org>,
        SeongJae Park <sj@...nel.org>, Jason Gunthorpe <jgg@...pe.ca>,
        Leon Romanovsky <leon@...nel.org>, Xu Xin <xu.xin16@....com.cn>,
        Chengming Zhou <chengming.zhou@...ux.dev>,
        Jann Horn <jannh@...gle.com>, Miaohe Lin <linmiaohe@...wei.com>,
        Naoya Horiguchi <nao.horiguchi@...il.com>,
        Pedro Falcato <pfalcato@...e.de>,
        Pasha Tatashin <pasha.tatashin@...een.com>,
        Rik van Riel <riel@...riel.com>, Harry Yoo <harry.yoo@...cle.com>,
        Hugh Dickins <hughd@...gle.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, linux-s390@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-arch@...r.kernel.org, damon@...ts.linux.dev
Subject: Re: [PATCH 02/16] mm: introduce leaf entry type and use to simplify
 leaf entry logic

On Wed, Nov 05, 2025 at 07:06:11PM +0000, Matthew Wilcox wrote:
> On Mon, Nov 03, 2025 at 12:31:43PM +0000, Lorenzo Stoakes wrote:
> > The kernel maintains leaf page table entries which contain either:
> >
> > - Nothing ('none' entries)
> > - Present entries (that is stuff the hardware can navigate without fault)
> > - Everything else that will cause a fault which the kernel handles
>
> The problem is that we're already using 'pmd leaf entries' to mean "this
> is a pointer to a PMD entry rather than a table of PTEs".  So I think
> we need a new name.  A boring name would be 'swent' (software entry).
> An acronym would be SWE.  In the XArray I distinguish between pointer
> entries and value entries -- would calling them value entries work here?
> Or we could call them something entirely different.  Say 'twig'.  Or
> 'cask'.
>

Yeah as discussed off-list I do concede 'leaf entry' is overloaded
vs. hardware leaf entries, I just found the idea of sw_leaf_entry_t a bit
gross and unclear.

Of course we now add a new ambiguity with this as really we do mean
software leaf entry.

How about:

soft_leaf_t

softleaf_xxx()

?

Cheers, Lorenzo