Re: [PATCH 5/9] MIPS: dump_tlb: Take global bit into account

[James Hogan <james.hogan@imgtec.com>]

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Hi Maciej,

On 16/05/15 01:44, Maciej W. Rozycki wrote:
> On Wed, 13 May 2015, James Hogan wrote:
> 
>> The TLB only matches the ASID when the global bit isn't set, so
>> dump_tlb() shouldn't really be skipping global entries just because the
>> ASID doesn't match. Fix the condition to read the TLB entry's global bit
>> from EntryLo0. Note that after a TLB read the global bits in both
>> EntryLo registers reflect the same global bit in the TLB entry.
>>
>> Signed-off-by: James Hogan <james.hogan@imgtec.com>
>> Cc: Ralf Baechle <ralf@linux-mips.org>
>> Cc: linux-mips@linux-mips.org
>> ---
>>  arch/mips/lib/dump_tlb.c | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/mips/lib/dump_tlb.c b/arch/mips/lib/dump_tlb.c
>> index 17d05caa776d..70e0a6bdb322 100644
>> --- a/arch/mips/lib/dump_tlb.c
>> +++ b/arch/mips/lib/dump_tlb.c
>> @@ -73,7 +73,8 @@ static void dump_tlb(int first, int last)
>>  		 */
>>  		if ((entryhi & ~0x1ffffUL) == CKSEG0)
>>  			continue;
>> -		if ((entryhi & 0xff) != asid)
>> +		/* ASID takes effect in absense of global bit */
> 
>  Typo here, s/absense/absence/.

Thanks!

> 
>> +		if (!(entrylo0 & 1) && (entryhi & 0xff) != asid)
> 
>  Hmm, it looks like r3k_dump_tlb.c will need a similar update.  I suggest 

Yes, quite possibly. Would you be happy to test such a patch (assuming
you have r3000 hardware available)? Patch 1 should allow the code to be
easily triggered.

> using _PAGE_GLOBAL and ASID_MASK rather than hardcoded 1 and 0xff.

Yeh, as you mentioned these describe the PTE rather than what goes in
EntryLo. Perhaps it makes sense to have a few more TLB dependent
definitions in mipsregs.h (patch 7 already adds a couple for RI/XI bits).

Cheers
James


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