Messages in this thread | | | Date | Fri, 30 Sep 2022 15:25:53 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH v3 08/10] x86/mtrr: let cache_aps_delayed_init replace mtrr_aps_delayed_init |
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On Fri, Sep 30, 2022 at 03:11:07PM +0200, Juergen Gross wrote: > Yes, this can be done. It would practically have to be the first one just > after CPUHP_BRINGUP_CPU.
Right.
> The question is whether we really want to call the MTRR/PAT initialization > on hotplugged cpus only after enabling interrupts. Note that the callbacks > are activated only at the end of start_secondary(), while today MTRR/PAT > initialization is called some time earlier by: > > start_secondary() > smp_callin() > smp_store_cpu_info() > identify_secondary_cpu() > mtrr_ap_init() > > I don't think this is a real problem, but I wanted to mention it.
Yep, I saw that too but I don't think there will be a problem either. I mean, it should be early enough as you point out not to need proper MTRR/PAT settings yet.
But we'll make sure we test this real good too.
> The next question would be, why MTRR/PAT init should be special > (meaning: why are all the other functions called that early not > realized via callbacks)?
Well, our init code is crazy. Frankly, I don't see why not more of the "init stuff on the freshly hotplugged CPU" work is done there...
> Is it just because of the special handling during boot/resume?
... unless this is the case, ofc. Right.
> It might be worth a discussion whether there shouldn't be a special group > of callbacks activated BEFORE interrupts are being enabled.
That's a good question. /me writes it down to ask tglx when he gets back.
I mean, that early I don't think it matters whether IRQs are enabled or not. But this'll need to be audited on a case by case basis. As I said, our boot code is nuts with stuff bolted on everywhere for whatever reasons.
> Thanks. I'll write a patch for that.
Thanks too.
-- Regards/Gruss, Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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