Re: [PATCH] powerpc/book3s64/radix/tlb: Determine hugepage flush correctly

[Michael Ellerman <mpe@ellerman.id.au>]

Nicholas Piggin <npiggin@gmail.com> writes:
> Excerpts from Aneesh Kumar K.V's message of May 13, 2020 1:06 pm:
>> With a 64K page size flush with start and end value as below
>> (start, end) = (721f680d0000, 721f680e0000) results in
>> (hstart, hend) = (721f68200000, 721f68000000)
>> 
>> Avoid doing a __tlbie_va_range with the wrong hstart and hend value in this
>> case.
>> 
>> __tlbie_va_range will skip the actual tlbie operation for start > end.
>> But we still end up doing the tlbie fixup.
>
> Hm, good catch.
>
>> Reported-by: Bharata B Rao <bharata@linux.ibm.com>
>> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
>> ---
>>  arch/powerpc/mm/book3s64/radix_tlb.c | 6 +++---
>>  1 file changed, 3 insertions(+), 3 deletions(-)
>> 
>> diff --git a/arch/powerpc/mm/book3s64/radix_tlb.c b/arch/powerpc/mm/book3s64/radix_tlb.c
>> index 758ade2c2b6e..d592f9e1c037 100644
>> --- a/arch/powerpc/mm/book3s64/radix_tlb.c
>> +++ b/arch/powerpc/mm/book3s64/radix_tlb.c
>> @@ -884,10 +884,10 @@ static inline void __radix__flush_tlb_range(struct mm_struct *mm,
>>  		if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
>>  			hstart = (start + PMD_SIZE - 1) & PMD_MASK;
>>  			hend = end & PMD_MASK;
>> -			if (hstart == hend)
>> -				hflush = false;
>> -			else
>> +			if (hstart < hend)
>>  				hflush = true;
>> +			else
>> +				hflush = false;
>
> We can probably get rid of the else part since it is already false.

Yeah I can do that when applying.

cheers