Re: [PATCH] MIPS: ASID conflict after CPU hotplug

["Kevin D. Kissell" <kevink@paralogos.com>]

On 11/21/10 19:41, Ralf Baechle wrote:
> ...
> Need to think a little about potencial consequences of your suggested
> patch.  It seems ok.  Kevin, what do you think?
>    
Since you ask, while I would imagine that Maksim's patch works fine for 
him, I'm not sure that it's really the right fix.  I never did succeed 
in getting CPU hotplugging working back in the 2.6.18 days, so I don't 
know as much about it as I'd like, but if per_cpu_trap_init() needs to 
be invoked on a hot plugin event, and if its behavior needs to be 
different , I'd really, really prefer to see that state propagated 
explicitly, rather than inferring it from whatever happens to be in 
cache/memory at cpu_data[cpu].asid_cache.  But beyond that, if the 
problem arises because setting cpu_data[cpu].asid_cache to a known 
initial state on a plugin event can conflict with the residual content 
of EntryHi, rather than creating a special case where we don't 
initialize the ASID cache, since we seem to be (re)initializing a lot of 
other privileged state, why aren't we also setting a known sane initial 
EntryHi value?   Wouldn't that be a cleaner fix?  (And I don't mean that 
as a rhetorical question - there may be very good reasons to let EntryHi 
values persist across hot unplug/plug events.  I just can't imagine them 
offhand over coffee.)

/K.