From: Matthew Wilcox <willy@infradead.org>
To: Oscar Salvador <osalvador@suse.de>
Cc: lsf-pc@lists.linux-foundation.org,
David Hildenbrand <david@redhat.com>,
Peter Xu <peterx@redhat.com>, Muchun Song <muchun.song@linux.dev>,
linux-mm@kvack.org
Subject: Re: [LSF/MM/BPF TOPIC] HugeTLB generic pagewalk
Date: Thu, 30 Jan 2025 22:46:37 +0000 [thread overview]
Message-ID: <Z5wBTdIOnAFr7L9E@casper.infradead.org> (raw)
In-Reply-To: <Z5vw82IhCV6tN1qG@localhost.localdomain>
On Thu, Jan 30, 2025 at 10:36:51PM +0100, Oscar Salvador wrote:
> HugeTLB has its own way of dealing with things.
> E.g: HugeTLB interprets everything as a pte: huge_pte_uffd_wp, huge_pte_clear_uffd_wp,
> huge_pte_dirty, huge_pte_modify, huge_pte_wrprotect etc.
This is a bug, not a feature. It makes some horrendous assumptions
about how each architecture encodes its ptes/pmd/puds (ie they're all
compatible). By and large they're mostly compatible, but there are some
awful hacks to work around the cases where they aren't.
> One of the challenges that this raises is that if we want pmd/pud walkers to
> be able to make sense of hugetlb stuff, we need to implement pud/pmd
> (maybe some pmd we already have because of THP) variants of those.
That's a good thing! typesafety is good! hugetlbfs tries to defeat it
and it works rather too well.
next prev parent reply other threads:[~2025-01-30 22:46 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-01-30 21:36 Oscar Salvador
2025-01-30 22:45 ` Peter Xu
2025-01-30 22:46 ` Matthew Wilcox [this message]
2025-01-30 23:19 ` David Hildenbrand
2025-01-31 15:42 ` Christophe Leroy
2025-02-04 20:19 ` David Hildenbrand
2025-02-03 10:10 ` Oscar Salvador
2025-02-04 20:40 ` David Hildenbrand
2025-02-05 9:33 ` Oscar Salvador
2025-02-11 13:31 ` David Hildenbrand
2025-02-12 9:13 ` Oscar Salvador
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