[MODERATED] Re: [PATCH v5 06/27] MDSv5 18

[Andi Kleen <ak@linux.intel.com>]

On Mon, Jan 21, 2019 at 04:41:50PM -0600, speck for Josh Poimboeuf wrote:
> On Fri, Jan 18, 2019 at 04:50:21PM -0800, speck for Andi Kleen wrote:
> > --- a/arch/x86/include/asm/clearcpu.h
> > +++ b/arch/x86/include/asm/clearcpu.h
> > @@ -20,6 +20,26 @@ static inline void clear_cpu(void)
> >  		[kernelds] "m" (kernel_ds));
> >  }
> >  
> > +/*
> > + * Clear CPU buffers before going idle, so that no state is leaked to SMT
> > + * siblings taking over thread resources.
> > + * Out of line to avoid include hell.
> > + *
> > + * Assumes that interrupts are disabled and only get reenabled
> > + * before idle, otherwise the data from a racing interrupt might not
> > + * get cleared. There are some callers who violate this,
> > + * but they are only used in unattackable cases, like CPU
> > + * offlining.
> > + */
> > +
> > +static inline void clear_cpu_idle(void)
> > +{
> > +	if (sched_smt_active()) {
> > +		clear_thread_flag(TIF_CLEAR_CPU);
> > +		clear_cpu();
> > +	}
> > +}
> > +
> >  DECLARE_STATIC_KEY_FALSE(force_cpu_clear);
> 
> This causes an error with CONFIG_ACPI_PROCESSOR_AGGREGATOR:
> 
>   ERROR: "sched_smt_present" [drivers/acpi/acpi_pad.ko] undefined!
> 
> because sched_smt_present isn't exported.

Yes it's a regression from the previous version. Just readd the hunk below.
I'll do so in the next version.

> 
> > diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
> > index b2131c4ea124..b4406ca1dfd7 100644
> > --- a/drivers/acpi/processor_idle.c
> > +++ b/drivers/acpi/processor_idle.c
> > @@ -33,6 +33,7 @@
> >  #include <linux/cpuidle.h>
> >  #include <linux/cpu.h>
> >  #include <acpi/processor.h>
> > +#include <asm/clearcpu.h>
> 
> This should be s/asm/linux/ because this code can be used by non-x86
> arches.

Ok.

-Andi


diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index b8cb9aad6b74..b9d2a617b105 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5982,6 +5982,7 @@ static inline int find_idlest_cpu(struct sched_domain *sd, struct task_struct *p
 
 #ifdef CONFIG_SCHED_SMT
 DEFINE_STATIC_KEY_FALSE(sched_smt_present);
+EXPORT_SYMBOL(sched_smt_present);
 
 static inline void set_idle_cores(int cpu, int val)
 {