Re: [PATCH] MIPS: tlbex: fix a missing statement for HUGETLB

[James Hogan <james@albanarts.com>]

Hi Huacai,

On Tuesday 29 July 2014 14:54:40 Huacai Chen wrote:
> In commit 2c8c53e28f1 (MIPS: Optimize TLB handlers for Octeon CPUs)
> build_r4000_tlb_refill_handler() is modified. But it doesn't compatible
> with the original code in HUGETLB case. Because there is a copy & paste
> error and one line of code is missing. It is very easy to produce a bug
> with LTP's hugemmap05 test.
> 
> Signed-off-by: Huacai Chen <chenhc@lemote.com>
> Signed-off-by: Binbin Zhou <zhoubb@lemote.com>
> Cc: <stable@vger.kernel.org>
> ---
>  arch/mips/mm/tlbex.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/arch/mips/mm/tlbex.c b/arch/mips/mm/tlbex.c
> index e80e10b..343fe0f 100644
> --- a/arch/mips/mm/tlbex.c
> +++ b/arch/mips/mm/tlbex.c
> @@ -1299,6 +1299,7 @@ static void build_r4000_tlb_refill_handler(void)
>  	}
>  #ifdef CONFIG_MIPS_HUGE_TLB_SUPPORT
>  	uasm_l_tlb_huge_update(&l, p);
> +	UASM_i_LW(&p, K0, 0, K1);
>  	build_huge_update_entries(&p, htlb_info.huge_pte, K1);
>  	build_huge_tlb_write_entry(&p, &l, &r, K0, tlb_random,
>  				   htlb_info.restore_scratch);

build_huge_tlb_write_entry only uses K0 as a temp and clobbers without using 
the value, so the K0 must be being used by the code generated by 
build_huge_update_entires, but the patch you mentioned changed the second 
argument from K0 to htlb_info.huge_pte.

So should the K0 in the new UASM_i_LW call be changed to htlb_info.huge_pte 
too?

(David Daney on Cc)

Thanks
James