linux-kernel - RE: [PATCH 1/1] x86/irq: Add hardcoded hypervisor interrupts to /proc/stat

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Date:   Wed, 22 Mar 2023 19:52:21 +0000
From:   "Michael Kelley (LINUX)" <mikelley@...rosoft.com>
To:     Dave Hansen <dave.hansen@...el.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "bp@...en8.de" <bp@...en8.de>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "hpa@...or.com" <hpa@...or.com>, "x86@...nel.org" <x86@...nel.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 1/1] x86/irq: Add hardcoded hypervisor interrupts to
 /proc/stat

From: Dave Hansen <dave.hansen@...el.com> Sent: Wednesday, March 22, 2023 11:07 AM
> 
> On 2/27/23 10:46, Michael Kelley wrote:
> > diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c
> > index 766ffe3..9f668d2 100644
> > --- a/arch/x86/kernel/irq.c
> > +++ b/arch/x86/kernel/irq.c
> > @@ -211,6 +211,13 @@ u64 arch_irq_stat_cpu(unsigned int cpu)
> >  #ifdef CONFIG_X86_MCE_THRESHOLD
> >  	sum += irq_stats(cpu)->irq_threshold_count;
> >  #endif
> > +#ifdef CONFIG_X86_HV_CALLBACK_VECTOR
> > +	sum += irq_stats(cpu)->irq_hv_callback_count;
> > +#endif
> > +#if IS_ENABLED(CONFIG_HYPERV)
> > +	sum += irq_stats(cpu)->irq_hv_reenlightenment_count;
> > +	sum += irq_stats(cpu)->hyperv_stimer0_count;
> > +#endif
> >  #ifdef CONFIG_X86_MCE
> >  	sum += per_cpu(mce_exception_count, cpu);
> >  	sum += per_cpu(mce_poll_count, cpu);
> 
> This seems fine, especially since arch_show_interrupts() has them.  But,
> what's with the "#if IS_ENABLED" versus the plain #ifdef?  Is there some
> difference I'm missing?  Why not just be consistent with the other code
> and use a plain #ifdef for both?

I'm following the coding pattern in arch_show_interrupts(), in irq_cpustat_t,
and most other places that test CONFIG_HYPERV.   Maybe all those existing
cases are a mis-application of Documentation/process/coding-style.rst
Section 21, which prefers "if (IS_ENABLED(CONFIG_HYPERV))" over
"#ifdef CONFIG_HYPERV".  "#if IS_ENABLED()" is not the same as
"if (IS_ENABLED())".  :-)

 Net, I don't have a strong preference either way.  

Michael