Re: [PATCH] MIPS: mm: tlb-r4k: Uniquify TLB entries on init

[Jiaxun Yang]

在2025年6月7日周六 上午3:48，Maciej W. Rozycki写道：
> On Thu, 5 Jun 2025, Jiaxun Yang wrote:
>
>> +static unsigned long r4k_safe_entryhi(void)
>> +{
>> +	int entry = current_cpu_data.tlbsize;
>> +	int old_index;
>> +
>> +	old_index = read_c0_index();
>> +	while (entry >= 0) {
> [...]
>> +		entry++;
>> +	}
>
>  Hmm, how is it supposed to work: you start from say 48 and then iterate 
> until 0x80000000 before giving up?  Also a signed overflow condition is UB 
> pre-C23, so the compiler may well optimise the loop control away.

Ah sorry I didn't realise it's a UB. However, this loop is likely to be
terminated very early as it should be fairly easily to find a free EntryHi
value with TLBP.

>
>  How did you verify this code?

Boot tested on Boston as well as M5150 simulation. I tried to manually setup a
TLB entry collision situation with Boot-MIPS.

>
>   Maciej

Thanks

-- 
- Jiaxun