Re: [PATCH 0/2] Fix dmar fault interrupt problems

[Chris Wright <chrisw@sous-sol.org>]

* Suresh Siddha (suresh.b.siddha@intel.com) wrote:
> On Tue, 2010-11-30 at 11:28 -0800, Chris Wright wrote:
> > AFAICT, it just becomes a duplicate call in a narrow window.
> > 
> > native_smp_prepare_cpus() (or APIC_init_uniprocessor()):
> >  enable_IR_x2apic()
> >   enable_IR()
> >    enable_intr_remapping() <-- clears faults
> >  default_setup_apic_routing()
> >    enable_drhd_fault_handling() <-- added call to clear faults
> > 
> > That's what I meant by not needed.
> 
> I agree that we will call clear faults twice.
> 
> With out the second clear fault, any fault in that narrow window of
> enabling intr-remapping and enabling fault handling will go unnoticed
> and block further faults getting reported.
> 
> I am not sure if the first fault is necessary. I can check and remove it
> if not needed.
> 
> Ideally we want to do something like:
> 
> Setup fault handling
> Clear any faults
> Enable intr-remapping

Agree, that's ideal.

> But fault handling interrupt configuration depends on the apic mode that
> gets selected based on whether intr-remapping was enabled successfully
> or not. And hence we were enabling fault handling after enabling the
> intr-remapping mode.
> 
> I can see if I can cleanup any of these flows for 2.6.38. For 2.6.37 and
> older kernels I would like to keep the patch simple.

Yup, makes sense.

thanks,
-chris