[PATCH v4 29/39] arm64: mte: Switch GCR_EL1 in kernel entry and exit

[Catalin Marinas]

On Fri, Oct 02, 2020 at 01:10:30AM +0200, Andrey Konovalov wrote:
> diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c
> index 7c67ac6f08df..d1847f29f59b 100644
> --- a/arch/arm64/kernel/mte.c
> +++ b/arch/arm64/kernel/mte.c
> @@ -23,6 +23,8 @@
>  #include <asm/ptrace.h>
>  #include <asm/sysreg.h>
>  
> +u64 gcr_kernel_excl __ro_after_init;
> +
>  static void mte_sync_page_tags(struct page *page, pte_t *ptep, bool check_swap)
>  {
>  	pte_t old_pte = READ_ONCE(*ptep);
> @@ -120,6 +122,13 @@ void *mte_set_mem_tag_range(void *addr, size_t size, u8 tag)
>  	return ptr;
>  }
>  
> +void mte_init_tags(u64 max_tag)
> +{
> +	u64 incl = GENMASK(max_tag & MTE_TAG_MAX, 0);

Nitpick: it's not obvious that MTE_TAG_MAX is a mask, so better write
this as GENMASK(min(max_tag, MTE_TAG_MAX), 0).

Otherwise it looks fine.

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