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Subject: Re: [PATCH 26/35] kasan, arm64: Enable TBI EL1
To:     Catalin Marinas <catalin.marinas@arm.com>
Cc:     Andrey Konovalov <andreyknvl@google.com>,
        Dmitry Vyukov <dvyukov@google.com>, 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-kernel@lists.infradead.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
References: <cover.1597425745.git.andreyknvl@google.com>
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 <20200827104033.GF29264@gaia> <9c53dfaa-119e-b12e-1a91-1f67f4aef503@arm.com>
 <20200827111344.GK29264@gaia>
From:   Vincenzo Frascino <vincenzo.frascino@arm.com>
Message-ID: <d6695105-0484-2013-1012-fa977644e8ad@arm.com>
Date:   Thu, 27 Aug 2020 12:17:19 +0100
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On 8/27/20 12:13 PM, Catalin Marinas wrote:
> On Thu, Aug 27, 2020 at 12:05:55PM +0100, Vincenzo Frascino wrote:
>> On 8/27/20 11:40 AM, Catalin Marinas 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.
>>
>> Not sure I understand... Enabling TBI1 only if MTE is present would break
>> KASAN_SW_TAGS which is based on TBI1 but not on MTE.
> 
> You keep the KASAN_SW_TAGS as above but for HW_TAGS, only set TBI1 later
> in __cpu_setup().
> 

Ok, sounds good.

-- 
Regards,
Vincenzo