Re: [PATCH v3 09/33] nds32: Cache and TLB routines

[Guo Ren]

On Wed, Dec 13, 2017 at 04:30:41PM +0800, Greentime Hu wrote:
> 2017-12-13 16:19 GMT+08:00 Guo Ren <ren_guo@xxxxxxxxx>:
> > On Wed, Dec 13, 2017 at 01:45:02PM +0800, Greentime Hu wrote:
> >
> >> I think it should be fine if an interruption between mtsr_dsb and
> >> tlbop_rwr because this is a optimization by sw.
> >
> > Fine? When there is an unexpected vaddr in SR_TLB_VPN, tlbop_rwr(*pte) will
> > break that vaddr's pfn in the CPU tlb-buffer entry. When linux access the
> > vaddr, it will get wrong data unless the entry has been replaced out.
> 
> Hi, Guo Ren:
> 
> Thanks. I get your point.
> It is needed to be protected.
> I will fix it in the next version patch.
> 
> if (vma->vm_mm == current->active_mm) {
>         local_irq_save(flags);
>         __nds32__mtsr_dsb(addr, NDS32_SR_TLB_VPN);
>         __nds32__tlbop_rwr(*pte);
>         __nds32__isb();
>         local_irq_restore(flags);
> }

If hardware tlbop_rwr could invalid NDS32_SR_TLB_VPN, then you needn't
protect.
I mean:
mtsr addr1 NDS32_SR_TLB_VPN
mtsr addr2 NDS32_SR_TLB_VPN
tlbop_rwr(*pte) // OK, and it will hit a hardware invalid bit internal.
tlbop_rwr(*pte) // SR_TLB_VPN invalided, then it will not cause problem.

:) How my idea?