RE: [PATCH RESEND 1/1] X86: Handle Hyper-V vmbus interrupts as special hypervisor interrupts

[KY Srinivasan <kys@microsoft.com>]

> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@suse.com]
> Sent: Thursday, January 24, 2013 3:48 AM
> To: KY Srinivasan
> Cc: olaf@aepfle.de; bp@alien8.de; apw@canonical.com; x86@kernel.org;
> tglx@linutronix.de; devel@linuxdriverproject.org; gregkh@linuxfoundation.org;
> jasowang@redhat.com; linux-kernel@vger.kernel.org; hpa@zytor.com
> Subject: Re: [PATCH RESEND 1/1] X86: Handle Hyper-V vmbus interrupts as
> special hypervisor interrupts
> 
> >>> On 24.01.13 at 02:17, "K. Y. Srinivasan" <kys@microsoft.com> wrote:
> > @@ -69,6 +74,11 @@ static void __init ms_hyperv_init_platform(void)
> >  	       ms_hyperv.features, ms_hyperv.hints);
> >
> >  	clocksource_register_hz(&hyperv_cs, NSEC_PER_SEC/100);
> > +
> > +	/*
> > +	 * Setup the IDT for hypervisor callback.
> > +	 */
> > +	alloc_intr_gate(HYPERVISOR_CALLBACK_VECTOR,
> hyperv_callback_vector);
> 
> Isn't doing this unconditionally here as problematic as the call to
> clocksource_register_hz() turned out to be when Xen's Hyper-V
> shim reacts to the CPUID inquiry above?

I was not sure what to make this conditional on at run-time. To the extent
that Xen emulation of Hyper-V is complete, this will be a problem. Does Xen
return all the "feature bits" of Hyper-V. I could discriminate on a feature that
Xen does not plan to emulate.

> 
> > @@ -77,3 +87,32 @@ const __refconst struct hypervisor_x86
> x86_hyper_ms_hyperv = {
> >  	.init_platform		= ms_hyperv_init_platform,
> >  };
> >  EXPORT_SYMBOL(x86_hyper_ms_hyperv);
> > +
> > +static int vmbus_irq = -1;
> > +static irq_handler_t vmbus_isr;
> > +
> > +void hv_register_vmbus_handler(int irq, irq_handler_t handler)
> > +{
> > +	vmbus_irq = irq;
> > +	vmbus_isr = handler;
> > +}
> > +EXPORT_SYMBOL_GPL(hv_register_vmbus_handler);
> > +
> > +void hyperv_vector_handler(struct pt_regs *regs)
> > +{
> > +	struct pt_regs *old_regs = set_irq_regs(regs);
> > +	struct irq_desc *desc;
> > +
> > +	irq_enter();
> > +#ifdef CONFIG_X86
> > +	exit_idle();
> > +#endif
> 
> This being in a file underneath arch/x86 - why the conditional?

Good point, I will fix that.
> 
> Jan
> 
>