Re: [Xen-devel] [PATCH v2 3/6] x86: track when in #MC context

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Mon, Feb 17, 2020 at 07:29:29PM +0000, Julien Grall wrote:
> Hi Roger,
> 
> On 17/02/2020 18:43, Roger Pau Monne wrote:
> > Add helpers to track when executing in #MC context. This is modeled
> > after the in_irq helpers.
> > 
> > Note that there are no users of in_mc() introduced by the change,
> > further users will be added by followup changes.
> > 
> > Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> > ---
> >   xen/arch/x86/cpu/mcheck/mce.c | 2 ++
> >   xen/include/asm-x86/hardirq.h | 5 +++++
> >   xen/include/xen/irq_cpustat.h | 1 +
> >   3 files changed, 8 insertions(+)
> > 
> > diff --git a/xen/arch/x86/cpu/mcheck/mce.c b/xen/arch/x86/cpu/mcheck/mce.c
> > index d61e582af3..93ed5752ac 100644
> > --- a/xen/arch/x86/cpu/mcheck/mce.c
> > +++ b/xen/arch/x86/cpu/mcheck/mce.c
> > @@ -93,7 +93,9 @@ void x86_mce_vector_register(x86_mce_vector_t hdlr)
> >   void do_machine_check(const struct cpu_user_regs *regs)
> >   {
> > +    mc_enter();
> >       _machine_check_vector(regs);
> > +    mc_exit();
> >   }
> >   /*
> > diff --git a/xen/include/asm-x86/hardirq.h b/xen/include/asm-x86/hardirq.h
> > index 34e1b49260..af3eab6a4d 100644
> > --- a/xen/include/asm-x86/hardirq.h
> > +++ b/xen/include/asm-x86/hardirq.h
> > @@ -8,6 +8,7 @@ typedef struct {
> >     unsigned int __softirq_pending;
> >     unsigned int __local_irq_count;
> >     unsigned int __nmi_count;
> > +   unsigned int mc_count;
> >     bool_t __mwait_wakeup;
> >   } __cacheline_aligned irq_cpustat_t;
> > @@ -18,6 +19,10 @@ typedef struct {
> >   #define irq_enter()       (local_irq_count(smp_processor_id())++)
> >   #define irq_exit()        (local_irq_count(smp_processor_id())--)
> > +#define in_mc()    (mc_count(smp_processor_id()) != 0)
> > +#define mc_enter() (mc_count(smp_processor_id())++)
> > +#define mc_exit()  (mc_count(smp_processor_id())--)
> > +
> >   void ack_bad_irq(unsigned int irq);
> >   extern void apic_intr_init(void);
> > diff --git a/xen/include/xen/irq_cpustat.h b/xen/include/xen/irq_cpustat.h
> > index 73629f6ec8..12b932fc39 100644
> > --- a/xen/include/xen/irq_cpustat.h
> > +++ b/xen/include/xen/irq_cpustat.h
> > @@ -26,5 +26,6 @@ extern irq_cpustat_t irq_stat[];
> >   #define local_irq_count(cpu)      __IRQ_STAT((cpu), __local_irq_count)
> >   #define nmi_count(cpu)            __IRQ_STAT((cpu), __nmi_count)
> >   #define mwait_wakeup(cpu) __IRQ_STAT((cpu), __mwait_wakeup)
> > +#define mc_count(cpu)              __IRQ_STAT((cpu), mc_count)
> 
> The header is only meant to contain arch-independent IRQ stats (see comment
> a few lines above). This is unlikely to be used on Arm, so can you move this
> into an x86 specific header?

Uh, sure. Sorry for not realizing this.

Thanks, Roger.

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