linux-kernel - Re: [PATCH 5/5] alloc_tag: config to store page allocation tag refs in page flags

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Message-ID: <ZsOtwhWC_JpgWe_J@casper.infradead.org>
Date: Mon, 19 Aug 2024 21:40:34 +0100
From: Matthew Wilcox <willy@...radead.org>
To: Suren Baghdasaryan <surenb@...gle.com>
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Subject: Re: [PATCH 5/5] alloc_tag: config to store page allocation tag refs
 in page flags

On Mon, Aug 19, 2024 at 01:39:16PM -0700, Suren Baghdasaryan wrote:
> On Mon, Aug 19, 2024 at 12:34 PM Matthew Wilcox <willy@...radead.org> wrote:
> > So if ALLOC_TAG_REF_WIDTH is big enough, it's going to force last_cpupid
> > into struct page.
> 
> Thanks for taking a look!
> Yes, but how is this field different from say KASAN_TAG_WIDTH which
> can also force last_cpupid out of page flags?

Because KASAN isn't for production use?

> >  That will misalign struct page and disable HVO -- with no warning!
> 
> mminit_verify_pageflags_layout already has a mminit_dprintk() to
> indicate this condition. Is that not enough?

Fair.