linux-kernel - Re: [PATCH v2 2/5] mm: add PTE_MARKER

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Message-ID: <f2c5ae69-3547-4118-ad30-9e398b2513b1@lucifer.local>
Date: Mon, 21 Oct 2024 16:41:44 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Vlastimil Babka <vbabka@...e.cz>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
        Suren Baghdasaryan <surenb@...gle.com>,
        "Liam R . Howlett" <Liam.Howlett@...cle.com>,
        Matthew Wilcox <willy@...radead.org>,
        "Paul E . McKenney" <paulmck@...nel.org>, Jann Horn <jannh@...gle.com>,
        David Hildenbrand <david@...hat.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Muchun Song <muchun.song@...ux.dev>,
        Richard Henderson <richard.henderson@...aro.org>,
        Ivan Kokshaysky <ink@...assic.park.msu.ru>,
        Matt Turner <mattst88@...il.com>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        "James E . J . Bottomley" <James.Bottomley@...senpartnership.com>,
        Helge Deller <deller@....de>, Chris Zankel <chris@...kel.net>,
        Max Filippov <jcmvbkbc@...il.com>, Arnd Bergmann <arnd@...db.de>,
        linux-alpha@...r.kernel.org, linux-mips@...r.kernel.org,
        linux-parisc@...r.kernel.org, linux-arch@...r.kernel.org,
        Shuah Khan <shuah@...nel.org>, Christian Brauner <brauner@...nel.org>,
        linux-kselftest@...r.kernel.org,
        Sidhartha Kumar <sidhartha.kumar@...cle.com>,
        Jeff Xu <jeffxu@...omium.org>, Christoph Hellwig <hch@...radead.org>,
        linux-api@...r.kernel.org, John Hubbard <jhubbard@...dia.com>
Subject: Re: [PATCH v2 2/5] mm: add PTE_MARKER_GUARD PTE marker

On Mon, Oct 21, 2024 at 04:33:19PM +0100, Lorenzo Stoakes wrote:
[snip]


> * For hardware poison markers it makes sense to drop them as you're
>   effectively saying 'I am done with this range that is now unbacked and
>   expect to get an empty page should I use it now'. UFFD WP I am not sure
>   about but presumably also fine.

[snip]

CORRECTION: (sorry multitasking atm now I have a non-melted CPU) UFFD WP is
            safe from MADV_FREE as it checks is_poisoned_swp_entry() which
            this patch updates to include guard pages, a change I will undo
            in v3. So disregard comment on UFFD WP here.