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List:       linux-mips
Subject:    Re: [PATCH] MIPS: tlbex: fix a missing statement for HUGETLB
From:       James Hogan <james.hogan () imgtec ! com>
Date:       2014-08-04 10:08:50
Message-ID: 53DF5BB2.70502 () imgtec ! com
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Hi Aurelien,

On 02/08/14 22:35, Aurelien Jarno wrote:
> On Thu, Jul 31, 2014 at 10:33:55AM -0700, David Daney wrote:
>> diff --git a/arch/mips/mm/tlbex.c b/arch/mips/mm/tlbex.c
>> index f99ec587..341add1 100644
>> --- a/arch/mips/mm/tlbex.c
>> +++ b/arch/mips/mm/tlbex.c
>> @@ -1299,6 +1299,8 @@ static void build_r4000_tlb_refill_handler(void)
>>         }
>>  #ifdef CONFIG_MIPS_HUGE_TLB_SUPPORT
>>         uasm_l_tlb_huge_update(&l, p);
>> +       if (!use_bbit_insns())
>> +               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);
> 
> This patch fixes the issue, thanks. That said it doesn't look fully
> correct. The test should be done the same way as for
> build_fast_tlb_refill_handler. For example the fast handler is not
> called on a 32-bit machine with bbit instructions, so it would need
> to reload K0.

In the non fast case build_is_huge_pte() will still use bbit1 if
available after restoring K0, and I don't think the bbit1 would clobber
K0 when the branch is taken, so I think the test for !use_bbit_insns()
is correct.

Cheers
James

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