Re: [Qemu-devel] [PATCH v3 08/15] target-mips: add BadInstr and BadInstrP support

[Leon Alrae]

Hi Yongbok,

On 29/10/14 13:55, Yongbok Kim wrote:
> On 24/10/2014 13:42, Leon Alrae wrote:
>>       case EXCP_TLBRI:
>>           cause = 19;
>> +        update_badinstr = 1;
>>           goto set_EPC;
>>       case EXCP_TLBXI:
>>           cause = 20;
> 
> TLBXI requires updating the register.

TLBXI exception can be generated by instruction fetch or MIPS16
PC-relative load. IIUC if TLBXI is caused by instruction fetch the value
stored in BadInstr is unpredictable as valid instruction word is not
available (the same case as TLB Refill - Instruction Fetch). Therefore
in context of Release 6 the implementation is correct. As far as MIPS16
is concerned, this is similar limitation which we discussed for patch #4
(i.e. MIPS16 PC-relative load should ignore RI bit).

Regards,
Leon