Re: [PATCH 11/12] MIPS: mm: Simplify build_update_entries

[James Hogan]

On Fri, Apr 15, 2016 at 11:36:59AM +0100, Paul Burton wrote:
> We can simplify build_update_entries by unifying the code for the 36 bit
> physical addressing with MIPS32 case with the general case, by using
> pte_off_ variables in all cases & handling the trivial
> _PAGE_GLOBAL_SHIFT == 0 case in build_convert_pte_to_entrylo. This
> leaves XPA as the only special case.
> 
> Signed-off-by: Paul Burton <paul.burton@xxxxxxxxxx>
> ---
> 
>  arch/mips/mm/tlbex.c | 38 +++++++++++++++++---------------------
>  1 file changed, 17 insertions(+), 21 deletions(-)
> 
> diff --git a/arch/mips/mm/tlbex.c b/arch/mips/mm/tlbex.c
> index 0bd3755..45234ad 100644
> --- a/arch/mips/mm/tlbex.c
> +++ b/arch/mips/mm/tlbex.c
> @@ -626,6 +626,11 @@ static void build_tlb_write_entry(u32 **p, struct uasm_label **l,
>  static __maybe_unused void build_convert_pte_to_entrylo(u32 **p,
>  							unsigned int reg)
>  {
> +	if (_PAGE_GLOBAL_SHIFT == 0) {
> +		/* pte_t is already in EntryLo format */
> +		return;
> +	}
> +
>  	if (cpu_has_rixi && _PAGE_NO_EXEC) {
>  		if (fill_includes_sw_bits) {
>  			UASM_i_ROTR(p, reg, reg, ilog2(_PAGE_GLOBAL));
> @@ -1003,10 +1008,17 @@ static void build_get_ptep(u32 **p, unsigned int tmp, unsigned int ptr)
>  
>  static void build_update_entries(u32 **p, unsigned int tmp, unsigned int ptep)
>  {
> -	if (config_enabled(CONFIG_XPA)) {
> -		int pte_off_even = sizeof(pte_t) / 2;
> -		int pte_off_odd = pte_off_even + sizeof(pte_t);
> +	int pte_off_even = 0;
> +	int pte_off_odd = sizeof(pte_t);
> +
> +	if (config_enabled(CONFIG_PHYS_ADDR_T_64BIT) &&
> +	    config_enabled(CONFIG_32BIT)) {
> +		/* The low 32 bits of EntryLo is stored in pte_high */
> +		pte_off_even += offsetof(pte_t, pte_high);
> +		pte_off_odd += offsetof(pte_t, pte_high);

pte_high doesn't exist unless CONFIG_CPU_MIPS32=y (e.g. you
can set CONFIG_CPU_MIPS64=y, CONFIG_CPU_MIPS32=n and CONFIG_32BIT=y).

With that fixed it looks good to me.
Reviewed-by: James Hogan <james.hogan@xxxxxxxxxx>

Cheers
James

> +	}
>  
> +	if (config_enabled(CONFIG_XPA)) {
>  		uasm_i_lw(p, tmp, pte_off_even, ptep); /* even pte */
>  		UASM_i_ROTR(p, tmp, tmp, ilog2(_PAGE_GLOBAL));
>  		UASM_i_MTC0(p, tmp, C0_ENTRYLO0);
> @@ -1025,24 +1037,8 @@ static void build_update_entries(u32 **p, unsigned int tmp, unsigned int ptep)
>  		return;
>  	}
>  
> -	/*
> -	 * 64bit address support (36bit on a 32bit CPU) in a 32bit
> -	 * Kernel is a special case. Only a few CPUs use it.
> -	 */
> -	if (config_enabled(CONFIG_PHYS_ADDR_T_64BIT) && !cpu_has_64bits) {
> -		int pte_off_even = sizeof(pte_t) / 2;
> -		int pte_off_odd = pte_off_even + sizeof(pte_t);
> -
> -		uasm_i_lw(p, tmp, pte_off_even, ptep); /* even pte */
> -		UASM_i_MTC0(p, tmp, C0_ENTRYLO0);
> -
> -		uasm_i_lw(p, ptep, pte_off_odd, ptep); /* odd pte */
> -		UASM_i_MTC0(p, ptep, C0_ENTRYLO1);
> -		return;
> -	}
> -
> -	UASM_i_LW(p, tmp, 0, ptep); /* get even pte */
> -	UASM_i_LW(p, ptep, sizeof(pte_t), ptep); /* get odd pte */
> +	UASM_i_LW(p, tmp, pte_off_even, ptep); /* get even pte */
> +	UASM_i_LW(p, ptep, pte_off_odd, ptep); /* get odd pte */
>  	if (r45k_bvahwbug())
>  		build_tlb_probe_entry(p);
>  	build_convert_pte_to_entrylo(p, tmp);
> -- 
> 2.8.0
>

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