Subject: Re: [PATCH v8 32/43] arm64: mte: Switch GCR_EL1 in kernel entry and exit

From: Catalin Marinas <[email-masked]>
Date: Thu, 5 Nov 2020 17:42:39 +0000

On Thu, Nov 05, 2020 at 12:18:47AM +0100, Andrey Konovalov wrote:
> From: Vincenzo Frascino <[email-masked]>
> 
> 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 <[email-masked]>
> Co-developed-by: Andrey Konovalov <[email-masked]>
> Signed-off-by: Andrey Konovalov <[email-masked]>

Reviewed-by: Catalin Marinas <[email-masked]>

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