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

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Message-ID: <27092660926e4d3f80394697cc0dc858@SN2PR03MB061.namprd03.prod.outlook.com>
Date:	Thu, 24 Jan 2013 16:07:40 +0000
From:	KY Srinivasan <kys@...rosoft.com>
To:	Jan Beulich <JBeulich@...e.com>
CC:	"olaf@...fle.de" <olaf@...fle.de>, "bp@...en8.de" <bp@...en8.de>,
	"apw@...onical.com" <apw@...onical.com>,
	"x86@...nel.org" <x86@...nel.org>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"jasowang@...hat.com" <jasowang@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"hpa@...or.com" <hpa@...or.com>
Subject: RE: [PATCH RESEND 1/1] X86: Handle Hyper-V vmbus interrupts as
 special hypervisor interrupts



> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@...e.com]
> Sent: Thursday, January 24, 2013 3:48 AM
> To: KY Srinivasan
> Cc: olaf@...fle.de; bp@...en8.de; apw@...onical.com; x86@...nel.org;
> tglx@...utronix.de; devel@...uxdriverproject.org; gregkh@...uxfoundation.org;
> jasowang@...hat.com; linux-kernel@...r.kernel.org; hpa@...or.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@...rosoft.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
> 
> 


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