Re: [PATCH 12/13] powerpc/perf: Thread imc cpuhotplug support

[Anju T Sudhakar]

On Thursday 23 March 2017 10:45 PM, Gautham R Shenoy wrote:
> Hi Maddy, Anju,
>
> On Thu, Mar 16, 2017 at 01:05:06PM +0530, Madhavan Srinivasan wrote:
> > From: Anju T Sudhakar <anju@xxxxxxxxxxxxxxxxxx>
> >
> > This patch adds support for thread IMC on cpuhotplug.
> >
> > When a cpu goes offline, the LDBAR for that cpu is disabled, and when it comes
> > back online the previous ldbar value is written back to the LDBAR for that cpu.
> >
> > To register the hotplug functions for thread_imc, a new state
> > CPUHP_AP_PERF_POWERPC_THREADIMC_ONLINE is added to the list of existing
> > states.
> >
> > Cc: Gautham R. Shenoy <ego@xxxxxxxxxxxxxxxxxx>
> > Cc: Balbir Singh <bsingharora@xxxxxxxxx>
> > Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
> > Cc: Paul Mackerras <paulus@xxxxxxxxx>
> > Cc: Anton Blanchard <anton@xxxxxxxxx>
> > Cc: Sukadev Bhattiprolu <sukadev@xxxxxxxxxxxxxxxxxx>
> > Cc: Michael Neuling <mikey@xxxxxxxxxxx>
> > Cc: Stewart Smith <stewart@xxxxxxxxxxxxxxxxxx>
> > Cc: Daniel Axtens <dja@xxxxxxxxxx>
> > Cc: Stephane Eranian <eranian@xxxxxxxxxx>
> > Signed-off-by: Anju T Sudhakar <anju@xxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Madhavan Srinivasan <maddy@xxxxxxxxxxxxxxxxxx>
> > ---
> >   arch/powerpc/perf/imc-pmu.c | 33 ++++++++++++++++++++++++++++-----
> >   include/linux/cpuhotplug.h  |  1 +
> >   2 files changed, 29 insertions(+), 5 deletions(-)
> >
> > diff --git a/arch/powerpc/perf/imc-pmu.c b/arch/powerpc/perf/imc-pmu.c
> > index 6802960db51c..2ff39fe2a5ce 100644
> > --- a/arch/powerpc/perf/imc-pmu.c
> > +++ b/arch/powerpc/perf/imc-pmu.c
> > @@ -687,6 +687,16 @@ static void cleanup_all_thread_imc_memory(void)
> >   	on_each_cpu(cleanup_thread_imc_memory, NULL, 1);
> >   }
> >
> > +static void thread_imc_update_ldbar(unsigned int cpu_id)
> > +{
> > +	u64 ldbar_addr, ldbar_value;
> > +
> > +	ldbar_addr = (u64)virt_to_phys((void *)per_cpu_add[cpu_id]);
> > +	ldbar_value = (ldbar_addr & (u64)THREAD_IMC_LDBAR_MASK) |
> > +			(u64)THREAD_IMC_ENABLE;
> > +	mtspr(SPRN_LDBAR, ldbar_value);
> > +}
> > +
> >   /*
> >    * Allocates a page of memory for each of the online cpus, and, writes the
> >    * physical base address of that page to the LDBAR for that cpu. This starts
> > @@ -694,20 +704,33 @@ static void cleanup_all_thread_imc_memory(void)
> >    */
> >   static void thread_imc_mem_alloc(void *dummy)
> >   {
> > -	u64 ldbar_addr, ldbar_value;
> >   	int cpu_id = smp_processor_id();
> >
> >   	per_cpu_add[cpu_id] = (u64)__get_free_pages(GFP_KERNEL | __GFP_ZERO,
> >   						    0);
> > -	ldbar_addr = (u64)virt_to_phys((void *)per_cpu_add[cpu_id]);
> > -	ldbar_value = (ldbar_addr & (u64)THREAD_IMC_LDBAR_MASK) |
> > -		(u64)THREAD_IMC_ENABLE;
> > -	mtspr(SPRN_LDBAR, ldbar_value);
> > +	thread_imc_update_ldbar(cpu_id);
> > +}
> > +
> > +static int ppc_thread_imc_cpu_online(unsigned int cpu)
> > +{
> > +	thread_imc_update_ldbar(cpu);
> > +	return 0;
> > +
> > +}
> > +
> > +static int ppc_thread_imc_cpu_offline(unsigned int cpu)
> > +{
> > +	mtspr(SPRN_LDBAR, 0);
> > +	return 0;
> >   }
> This patch looks ok to me.
>
> So it appears that in case of a full-core deep stop entry/exit you
> will need to save/restore LDBAR as well. But I will take it up for the
> next set of stop cleanups.
>
> For this patch,
> Reviewed-by: Gautham R. Shenoy <ego@xxxxxxxxxxxxxxxxxx>

Thank you for  reviewing the patch Gautham.

-Anju

> >   void thread_imc_cpu_init(void)
> >   {
> >   	on_each_cpu(thread_imc_mem_alloc, NULL, 1);
> > +	cpuhp_setup_state(CPUHP_AP_PERF_POWERPC_THREADIMC_ONLINE,
> > +			  "POWER_THREAD_IMC_ONLINE",
> > +			   ppc_thread_imc_cpu_online,
> > +			   ppc_thread_imc_cpu_offline);
> >   }
> >
> >   static void thread_imc_ldbar_disable(void *dummy)
> > diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
> > index abde85d9511a..724df46b2c3c 100644
> > --- a/include/linux/cpuhotplug.h
> > +++ b/include/linux/cpuhotplug.h
> > @@ -138,6 +138,7 @@ enum cpuhp_state {
> >   	CPUHP_AP_PERF_ARM_L2X0_ONLINE,
> >   	CPUHP_AP_PERF_POWERPC_NEST_ONLINE,
> >   	CPUHP_AP_PERF_POWERPC_COREIMC_ONLINE,
> > +	CPUHP_AP_PERF_POWERPC_THREADIMC_ONLINE,
> >   	CPUHP_AP_PERF_ARM_QCOM_L2_ONLINE,
> >   	CPUHP_AP_WORKQUEUE_ONLINE,
> >   	CPUHP_AP_RCUTREE_ONLINE,
> > --
> > 2.7.4
> --
> Thanks and Regards
> gautham.