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Date:   Thu, 5 Nov 2020 17:42:39 +0000
From:   Catalin Marinas <catalin.marinas@arm.com>
To:     Andrey Konovalov <andreyknvl@google.com>
Cc:     Will Deacon <will.deacon@arm.com>,
        Vincenzo Frascino <vincenzo.frascino@arm.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Alexander Potapenko <glider@google.com>,
        Marco Elver <elver@google.com>,
        Evgenii Stepanov <eugenis@google.com>,
        Branislav Rankov <Branislav.Rankov@arm.com>,
        Kevin Brodsky <kevin.brodsky@arm.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        kasan-dev@googlegroups.com, linux-arm-kernel@lists.infradead.org,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v8 32/43] arm64: mte: Switch GCR_EL1 in kernel entry and
 exit
Message-ID: <20201105174239.GI30030@gaia>
References: <cover.1604531793.git.andreyknvl@google.com>
 <5d9ece04df8e9d60e347a2f6f96b8c52316bfe66.1604531793.git.andreyknvl@google.com>
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On Thu, Nov 05, 2020 at 12:18:47AM +0100, Andrey Konovalov wrote:
> From: Vincenzo Frascino <vincenzo.frascino@arm.com>
> 
> When MTE is present, the GCR_EL1 register contains the tags mask that
> allows to exclude tags from the random generation via the IRG instruction.
> 
> With the introduction of the new Tag-Based KASAN API that provides a
> mechanism to reserve tags for special reasons, the MTE implementation
> has to make sure that the GCR_EL1 setting for the kernel does not affect
> the userspace processes and viceversa.
> 
> Save and restore the kernel/user mask in GCR_EL1 in kernel entry and exit.
> 
> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
> Co-developed-by: Andrey Konovalov <andreyknvl@google.com>
> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>