[PATCH] arm64: Cleanup __cpu_set_tcr_t0sz()

[Seongsu Park]

Dear All,

Please check this patch.
I think this patch is appropriate.

Thanks.
Seongsu Park.

> -----Original Message-----
> From: Seongsu Park <sgsu.park at samsung.com>
> Sent: Thursday, May 23, 2024 9:22 PM
> To: catalin.marinas at arm.com; will at kernel.org; ardb at kernel.org;
> mark.rutland at arm.com
> Cc: linux-arm-kernel at lists.infradead.org; linux-kernel at vger.kernel.org;
> infinite.run at gmail.com; sgsu.park at samsung.com
> Subject: [PATCH] arm64: Cleanup __cpu_set_tcr_t0sz()
> 
> The T0SZ field of TCR_EL1 occupies bits 0-5 of the register and encode the
> virtual address space translated by TTBR0_EL1. When updating the field,
> for example because we are switching to/from the idmap page-table,
> __cpu_set_tcr_t0sz() erroneously treats its 't0sz' argument as unshifted,
> resulting in harmless but confusing double shifts by 0 in the code.
> 
> Co-developed-by: Leem ChaeHoon <infinite.run at gmail.com>
> Signed-off-by: Leem ChaeHoon <infinite.run at gmail.com>
> Signed-off-by: Seongsu Park <sgsu.park at samsung.com>
> ---
>  arch/arm64/include/asm/mmu_context.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/mmu_context.h
> b/arch/arm64/include/asm/mmu_context.h
> index c768d16b81a4..bd19f4c758b7 100644
> --- a/arch/arm64/include/asm/mmu_context.h
> +++ b/arch/arm64/include/asm/mmu_context.h
> @@ -72,11 +72,11 @@ static inline void __cpu_set_tcr_t0sz(unsigned long
> t0sz)  {
>  	unsigned long tcr = read_sysreg(tcr_el1);
> 
> -	if ((tcr & TCR_T0SZ_MASK) >> TCR_T0SZ_OFFSET == t0sz)
> +	if ((tcr & TCR_T0SZ_MASK) == t0sz)
>  		return;
> 
>  	tcr &= ~TCR_T0SZ_MASK;
> -	tcr |= t0sz << TCR_T0SZ_OFFSET;
> +	tcr |= t0sz;
>  	write_sysreg(tcr, tcr_el1);
>  	isb();
>  }
> --
> 2.34.1