Re: [Qemu-devel] [PATCH v5 30/33] target-arm/cpu: don't reset TLB structures, use cputlb to do it

[Peter Maydell]

On 28 October 2016 at 09:38, Alex Bennée <address@hidden> wrote:
>
> Richard Henderson <address@hidden> writes:
>> And don't we (or if not, shouldn't we)
>> handle the tlb_flush generically for reset?
>
> Probably. tlb_flush seems to be one of those things liberally sprinkled
> in the arch code for all sorts of things but certainly cpu_reset is one
> we could make the call from generic code.

I think the theory I formed last time I looked at it is that
if your CPU has no state which would require you to flush the
TLB when it changes, then there's no need to flush the TLB
on reset -- any entries still in the TLB from before reset are
still valid after reset. For ARM a CPU reset will reset state
like the ASID and the MMU-enabled bit which require a TLB flush
on change, so we have to call tlb_flush here.

You could argue that the set of CPUs which don't require a
tlb flush on reset are not worth trying to optimise for
like this and we should just do it generically.

thanks
-- PMM