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From:   Andrey Konovalov <andreyknvl@google.com>
Date:   Tue, 8 Sep 2020 15:18:04 +0200
Message-ID: <CAAeHK+x_B+R3VcXndaQ=rwOExyQeFZEKZX-33oStiDFu1qePyg@mail.gmail.com>
Subject: Re: [PATCH 26/35] kasan, arm64: Enable TBI EL1
To:     Catalin Marinas <catalin.marinas@arm.com>
Cc:     Dmitry Vyukov <dvyukov@google.com>,
        Vincenzo Frascino <vincenzo.frascino@arm.com>,
        kasan-dev <kasan-dev@googlegroups.com>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Alexander Potapenko <glider@google.com>,
        Marco Elver <elver@google.com>,
        Evgenii Stepanov <eugenis@google.com>,
        Elena Petrova <lenaptr@google.com>,
        Branislav Rankov <Branislav.Rankov@arm.com>,
        Kevin Brodsky <kevin.brodsky@arm.com>,
        Will Deacon <will.deacon@arm.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Linux Memory Management List <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>
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On Thu, Aug 27, 2020 at 12:40 PM Catalin Marinas
<catalin.marinas@arm.com> wrote:
>
> On Fri, Aug 14, 2020 at 07:27:08PM +0200, Andrey Konovalov wrote:
> > diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
> > index 152d74f2cc9c..6880ddaa5144 100644
> > --- a/arch/arm64/mm/proc.S
> > +++ b/arch/arm64/mm/proc.S
> > @@ -38,7 +38,7 @@
> >  /* PTWs cacheable, inner/outer WBWA */
> >  #define TCR_CACHE_FLAGS      TCR_IRGN_WBWA | TCR_ORGN_WBWA
> >
> > -#ifdef CONFIG_KASAN_SW_TAGS
> > +#if defined(CONFIG_KASAN_SW_TAGS) || defined(CONFIG_KASAN_HW_TAGS)
> >  #define TCR_KASAN_FLAGS TCR_TBI1
> >  #else
> >  #define TCR_KASAN_FLAGS 0
>
> I prefer to turn TBI1 on only if MTE is present. So on top of the v8
> user series, just do this in __cpu_setup.

Started working on this, but realized that I don't understand what
exactly is suggested here. TCR_KASAN_FLAGS are used in __cpu_setup(),
so this already happens in __cpu_setup().

Do you mean that TBI1 should be enabled when CONFIG_ARM64_MTE is
enabled, but CONFIG_KASAN_HW_TAGS is disabled?