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    SubjectRe: [PATCH 26/35] kasan, arm64: Enable TBI EL1
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    Hi Andrey,

    On 8/27/20 1:43 PM, Andrey Konovalov wrote:
    > On Thu, Aug 27, 2020 at 1:15 PM Vincenzo Frascino
    > <vincenzo.frascino@arm.com> wrote:
    >>
    >>
    >>
    >> 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.
    >
    > Sounds good to me too.
    >
    > Vincenzo, could you take care of Catalin's comments on your (arm64)
    > patches, do the rebase onto user mte v8, and share it with me? I'll
    > work on KASAN changes in the meantime, and then integrate everything
    > together for v2.
    >

    I am happy to do that. I will be on holiday though from this Saturday till the
    September, 9. After that I will start the rebasing.

    > Perhaps the best way to test only the arm64 part is writing a simple
    > module that causes an MTE fault. (At least that's what I did when I
    > was testing core in-kernel MTE patches separately.) Or reuse this
    > series, all KASAN patches should rebase cleanly on top of the latest
    > mainline.
    >

    I can reuse the patches as they are, unless they require changes when I start
    rebasing. In such a case to not duplicate the work I will scale back to use a
    simple module.

    --
    Regards,
    Vincenzo

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