linux-kernel - Re: [PATCH 3/5] kasan, mm: integrate page_alloc init with HW

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Message-ID: <CAAeHK+zGDDhpzHqBrKcYhY3UvDG8iXfkCBVQ-5Se0QyESpQ91Q@mail.gmail.com>
Date:   Mon, 8 Mar 2021 15:14:21 +0100
From:   Andrey Konovalov <andreyknvl@...gle.com>
To:     Marco Elver <elver@...gle.com>
Cc:     Alexander Potapenko <glider@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Peter Collingbourne <pcc@...gle.com>,
        Evgenii Stepanov <eugenis@...gle.com>,
        Branislav Rankov <Branislav.Rankov@....com>,
        Kevin Brodsky <kevin.brodsky@....com>,
        kasan-dev <kasan-dev@...glegroups.com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/5] kasan, mm: integrate page_alloc init with HW_TAGS

On Mon, Mar 8, 2021 at 12:35 PM Marco Elver <elver@...gle.com> wrote:
>
> > -     kasan_free_nondeferred_pages(page, order, fpi_flags);
> > +     init = want_init_on_free();
> > +     if (init && !IS_ENABLED(CONFIG_KASAN_HW_TAGS))
>
> Doing the !IS_ENABLED(CONFIG_KASAN_HW_TAGS) check is awkward, and
> assumes internal knowledge of the KASAN implementation and how all
> current and future architectures that support HW_TAGS work.
>
> Could we instead add a static inline helper to <linux/kasan.h>, e.g.
> kasan_supports_init() or so?
>
> That way, these checks won't grow uncontrollable if a future
> architecture implements HW_TAGS but not init.

Good idea, I'll add a helper in v2.

> Hmm, KASAN certainly "supports" memory initialization always. So maybe
> "kasan_has_accelerated_init()" is more accurate?  I leave it to you to
> decide what the best option is.

Let's call it kasan_has_integrated_init().

Thanks!