linux-kernel - RE: [PATCH 06/32] x86/intel_rdt: Hot cpu support for Cache Allocation

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Date:	Thu, 14 Jul 2016 22:58:21 +0000
From:	"Yu, Fenghua" <fenghua.yu@...el.com>
To:	David Carrillo-Cisneros <davidcc@...gle.com>
CC:	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...e.hu>,
	"Anvin, H Peter" <h.peter.anvin@...el.com>,
	"Luck, Tony" <tony.luck@...el.com>, Tejun Heo <tj@...nel.org>,
	Borislav Petkov <bp@...e.de>,
	Stephane Eranian <eranian@...gle.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	"Shankar, Ravi V" <ravi.v.shankar@...el.com>,
	Vikas Shivappa <vikas.shivappa@...ux.intel.com>,
	"Prakhya, Sai Praneeth" <sai.praneeth.prakhya@...el.com>,
	linux-kernel <linux-kernel@...r.kernel.org>, x86 <x86@...nel.org>
Subject: RE: [PATCH 06/32] x86/intel_rdt: Hot cpu support for Cache
 Allocation

> 
> > +static inline void intel_rdt_cpu_start(int cpu) {
> > +       struct intel_pqr_state *state = &per_cpu(pqr_state, cpu);
> > +
> > +       state->closid = 0;
> > +       mutex_lock(&rdt_group_mutex);
> > +       if (rdt_cpumask_update(cpu))
> > +               smp_call_function_single(cpu, cbm_update_msrs, NULL, 1);
> > +       mutex_unlock(&rdt_group_mutex);
> 
> what happens if cpu's with a cache_id not available at boot comes online?

For L3, that case happens when a new socket is hot plugged into the platform.
We don't handle that right now because that needs platform support and I don't
have that kind of platform to test.

But maybe I can add that support in code and do a test in a simulated mode.
Basically that will create a new domain for the new cache_id.

Thanks.

-Fenghua