linux-kernel - Re: [Xen-devel] [PATCH 7/7] xen: Enable event channel of PV extension of HVM

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Date:	Mon, 8 Mar 2010 17:10:56 +0000
From:	Stefano Stabellini <stefano.stabellini@...citrix.com>
To:	Sheng Yang <sheng@...ux.intel.com>
CC:	Jeremy Fitzhardinge <Jeremy.Fitzhardinge@...rix.com>,
	Keir Fraser <Keir.Fraser@...citrix.com>,
	Ingo Molnar <mingo@...e.hu>,
	Ian Pratt <Ian.Pratt@...citrix.com>,
	xen-devel <xen-devel@...ts.xensource.com>,
	Ian Campbell <Ian.Campbell@...citrix.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [Xen-devel] [PATCH 7/7] xen: Enable event channel of PV extension
 of HVM

I think that mapping interrupts into VIRQs is a bad idea: you should map
interrupts into pirqs instead, the code exists already on the kernel
side so we don't need to do any (ugly) change there.
Look at xen_setup_pirqs() to get an idea about how it works, in my patch
series enabling pirq\interrupt mappings is basically a one line change.
Besides pirqs and interrupts can coexist without problems and even make
pv on hvm work out of the box.

Even though you don't seem interested, I am still open on collaborating
with you to complete this patch series.

On Mon, 8 Mar 2010, Sheng Yang wrote:
> @@ -944,3 +958,51 @@ void __init xen_init_IRQ(void)
> 
>         irq_ctx_init(smp_processor_id());
>  }
> +
> +void __init xen_hvm_pv_evtchn_init_IRQ(void)
> +{
> +       int i;
> +
> +       xen_init_IRQ();
> +       for (i = 0; i < NR_IRQS_LEGACY; i++) {
> +               struct evtchn_bind_virq bind_virq;
> +               struct irq_desc *desc = irq_to_desc(i);
> +               int virq, evtchn;
> +
> +               virq = i + VIRQ_EMUL_PIN_START;
> +               bind_virq.virq = virq;
> +               bind_virq.vcpu = 0;
> +
> +               if (HYPERVISOR_event_channel_op(EVTCHNOP_bind_virq,
> +                                               &bind_virq) != 0)
> +                       BUG();
> +
> +               evtchn = bind_virq.port;
> +               evtchn_to_irq[evtchn] = i;
> +               irq_info[i] = mk_virq_info(evtchn, virq);
> +
> +               desc->status = IRQ_DISABLED;
> +               desc->action = NULL;
> +               desc->depth = 1;
> +
> +               /*
> +                * 16 old-style INTA-cycle interrupts:
> +                */
> +               set_irq_chip_and_handler_name(i, &xen_dynamic_chip,
> +                                       handle_level_irq, "event");
> +       }
> +
> +       /*
> +        * Cover the whole vector space, no vector can escape
> +        * us. (some of these will be overridden and become
> +        * 'special' SMP interrupts)
> +        */
> +       for (i = 0; i < (NR_VECTORS - FIRST_EXTERNAL_VECTOR); i++) {
> +               int vector = FIRST_EXTERNAL_VECTOR + i;
> +               if (vector != IA32_SYSCALL_VECTOR)
> +                       set_intr_gate(vector, interrupt[i]);
> +       }
> +
> +       /* generic IPI for platform specific use, now used for HVM evtchn */
> +       alloc_intr_gate(X86_PLATFORM_IPI_VECTOR, x86_platform_ipi);
> +}

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