linux-kernel - Re: [PATCH RFC 14/14] mm: rename vm_ops->find_special_page() to vm_ops->find_normal

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Message-ID: <417888bf-db7d-4334-a8df-678c14c0d442@redhat.com>
Date: Mon, 14 Jul 2025 16:19:56 +0200
From: David Hildenbrand <david@...hat.com>
To: Oscar Salvador <osalvador@...e.de>
Cc: linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
 linux-mm@...ck.org, nvdimm@...ts.linux.dev,
 Andrew Morton <akpm@...ux-foundation.org>, Juergen Gross <jgross@...e.com>,
 Stefano Stabellini <sstabellini@...nel.org>,
 Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>,
 Dan Williams <dan.j.williams@...el.com>, Alistair Popple
 <apopple@...dia.com>, Matthew Wilcox <willy@...radead.org>,
 Jan Kara <jack@...e.cz>, Alexander Viro <viro@...iv.linux.org.uk>,
 Christian Brauner <brauner@...nel.org>, Zi Yan <ziy@...dia.com>,
 Baolin Wang <baolin.wang@...ux.alibaba.com>,
 Lorenzo Stoakes <lorenzo.stoakes@...cle.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>, Vlastimil Babka <vbabka@...e.cz>,
 Mike Rapoport <rppt@...nel.org>, Suren Baghdasaryan <surenb@...gle.com>,
 Michal Hocko <mhocko@...e.com>, Jann Horn <jannh@...gle.com>,
 Pedro Falcato <pfalcato@...e.de>, David Vrabel <david.vrabel@...rix.com>
Subject: Re: [PATCH RFC 14/14] mm: rename vm_ops->find_special_page() to
 vm_ops->find_normal_page()

On 25.06.25 11:34, Oscar Salvador wrote:
> On Tue, Jun 17, 2025 at 05:43:45PM +0200, David Hildenbrand wrote:
>> ... and hide it behind a kconfig option. There is really no need for
>> any !xen code to perform this check.
>>
>> The naming is a bit off: we want to find the "normal" page when a PTE
>> was marked "special". So it's really not "finding a special" page.
>>
>> Improve the documentation, and add a comment in the code where XEN ends
>> up performing the pte_mkspecial() through a hypercall. More details can
>> be found in commit 923b2919e2c3 ("xen/gntdev: mark userspace PTEs as
>> special on x86 PV guests").
> 
> Looks good to me.
> Since this seems a "mistake" from the past we don't want to repeat, I wonder
> whether we could seal FIND_NORMAL_PAGE somehow, and scream if someone
> tries to enable it on !XEN environments.

Hm, probably not that easy. I mean, as long as we cannot get rid of the 
XEN stuff, we don't particularly care about new users ... and it seems 
unlikely to get rid of that XEN stuff :(

-- 
Cheers,

David / dhildenb