On 28.09.22 18:12, Borislav Petkov wrote:
> On Wed, Sep 28, 2022 at 03:43:56PM +0200, Juergen Gross wrote:
>> Would you feel better with adding a new enum member CPUHP_AP_CACHECTRL_ONLINE?
>>
>> This would avoid a possible source of failure during resume in case no slot
>> for CPUHP_AP_ONLINE_DYN is found (quite improbable, but in theory possible).
> 
> Let's keep that in the bag for the time when we get to cross that bridge.
> 
>> You wouldn't want to do that there, as there are multiple places where
>> pm_sleep_enable_secondary_cpus() is being called.
> 
> We want all of them, I'd say. They're all some sort of suspend AFAICT.
> But yes, if we get to do it, that would need a proper audit.
> 
>> Additionally not all cases are coming in via
>> pm_sleep_enable_secondary_cpus(), as there is e.g. a call of
>> suspend_enable_secondary_cpus() from kernel_kexec(), which wants to
>> have the same handling.
> 
> Which means, more hairy.
> 
>> arch_thaw_secondary_cpus_begin() and arch_thaw_secondary_cpus_end() are
>> the functions to mark start and end of the special region where the
>> delayed MTRR setup should happen.
> 
> Yap, it seems like the best solution at the moment. Want me to do a
> proper patch and test it on real hw?

I can do that.


Juergen