Re: [Xen-devel] [RFC][PATCH 09/10] xen/hybrid: Make event channelwork with QEmu emulated devices

[Jeremy Fitzhardinge]

On 09/16/09 01:42, Sheng Yang wrote:
> We mapped each IOAPIC pin to a VIRQ, so that we can deliver interrupt through
> these VIRQs.
>
> We also use GENERIC_INTERRUPT_VECTOR as the noficiation vector for hypervisor
> to notify guest about the event.
>
> Then we don't need IOAPIC/LAPIC now...
>   

I commented a bit more below, but this patch is pretty unpleasant.  It
certainly can't be used in this form.

> Signed-off-by: Sheng Yang <sheng@xxxxxxxxxxxxxxx>
> ---
>  arch/x86/kernel/smpboot.c   |   14 ++++++++++++
>  arch/x86/xen/enlighten.c    |   49 +++++++++++++++++++++++++++++++++++++++++++
>  arch/x86/xen/irq.c          |   15 +++++++++++-
>  drivers/xen/events.c        |   47 +++++++++++++++++++++++++++++++++++++++++
>  include/xen/events.h        |    1 +
>  include/xen/hvm.h           |    5 ++++
>  include/xen/interface/xen.h |    6 ++++-
>  7 files changed, 134 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
> index 58d24ef..39c1890 100644
> --- a/arch/x86/kernel/smpboot.c
> +++ b/arch/x86/kernel/smpboot.c
> @@ -67,6 +67,10 @@
>  
>  #include <asm/smpboot_hooks.h>
>  
> +#ifdef CONFIG_XEN
> +#include <asm/xen/hypervisor.h>
> +#endif
> +
>  #ifdef CONFIG_X86_32
>  u8 apicid_2_node[MAX_APICID];
>  static int low_mappings;
> @@ -1062,6 +1066,11 @@ void __init native_smp_prepare_cpus(unsigned int max_cpus)
>  	}
>  	set_cpu_sibling_map(0);
>  
> +#ifdef CONFIG_XEN
> +	if (xen_hybrid_evtchn_enabled())
> +		goto out;
> +#endif
> +
>  	enable_IR_x2apic();
>  #ifdef CONFIG_X86_64
>  	default_setup_apic_routing();
> @@ -1131,6 +1140,11 @@ void __init native_smp_cpus_done(unsigned int max_cpus)
>  {
>  	pr_debug("Boot done.\n");
>  
> +#ifdef CONFIG_XEN
> +	if (xen_hybrid_evtchn_enabled())
> +		return;
> +#endif
>   

These changes will never fly. I'm aggressively moving away from making
any Xen-specific changes in core files for dom0; I don't want to add any
more for a hybrid mode.  (I'd really prefer not to have a hybrid mode at
all.)

> +
>  	impress_friends();
>  #ifdef CONFIG_X86_IO_APIC
>  	setup_ioapic_dest();
> diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
> index 18aba22..f515584 100644
> --- a/arch/x86/xen/enlighten.c
> +++ b/arch/x86/xen/enlighten.c
> @@ -54,6 +54,10 @@
>  #include <asm/reboot.h>
>  
>  #include <xen/hvm.h>
> +#include <xen/events.h>
> +#include <asm/acpi.h>
> +#include <asm/irq_vectors.h>
> +#include <asm/irq.h>
>  
>  #include "xen-ops.h"
>  #include "mmu.h"
> @@ -1055,6 +1059,8 @@ static void __init xen_hybrid_banner(void)
>  
>  	if (xen_hybrid_timer_enabled())
>  		printk(KERN_INFO "Hybrid feature: PV Timer enabled\n");
> +	if (xen_hybrid_evtchn_enabled())
> +		printk(KERN_INFO "Hybrid feature: Event channel enabled\n");
>  }
>  
>  static int xen_para_available(void)
> @@ -1102,6 +1108,10 @@ static int init_hybrid_info(void)
>  		xen_hybrid_status |= XEN_HYBRID_TIMER_ENABLED;
>  		flags |= HVM_HYBRID_TIMER;
>  	}
> +	if (edx & XEN_CPUID_FEAT2_HYBRID_EVTCHN) {
> +		xen_hybrid_status |= XEN_HYBRID_EVTCHN_ENABLED;
> +		flags |= HVM_HYBRID_EVTCHN;
> +	}
>  
>  	/* We only support 1 page of hypercall for now */
>  	if (pages != 1)
> @@ -1144,9 +1154,27 @@ static int __init init_shared_info(void)
>  	return 0;
>  }
>  
> +static int set_callback_via(uint64_t via)
> +{
> +	struct xen_hvm_param a;
> +
> +	a.domid = DOMID_SELF;
> +	a.index = HVM_PARAM_CALLBACK_IRQ;
> +	a.value = via;
> +	return HYPERVISOR_hvm_op(HVMOP_set_param, &a);
> +}
> +
> +void do_hybrid_intr(void)
> +{
> +	per_cpu(irq_count, smp_processor_id())++;
> +	xen_evtchn_do_upcall(get_irq_regs());
> +	per_cpu(irq_count, smp_processor_id())--;
> +}
> +
>  void __init xen_start_hybrid(void)
>  {
>  	int r;
> +	uint64_t callback_via;
>  
>  	if (!xen_para_available())
>  		return;
> @@ -1163,5 +1191,26 @@ void __init xen_start_hybrid(void)
>  		pv_time_ops = xen_time_ops;
>  		pv_apic_ops = xen_apic_ops;
>  	}
> +
> +	if (xen_hybrid_evtchn_enabled()) {
> +		pv_apic_ops = xen_apic_ops;
> +#ifdef CONFIG_X86_LOCAL_APIC
> +		/*
> +		 * set up the basic apic ops.
> +		 */
> +		set_xen_basic_apic_ops();
> +#endif
> +
> +		callback_via = HVM_CALLBACK_VECTOR(GENERIC_INTERRUPT_VECTOR);
> +		set_callback_via(callback_via);
> +
> +		generic_interrupt_extension = do_hybrid_intr;
> +
> +		disable_acpi();
> +		disable_apic = 1;
> +
> +		machine_ops = xen_machine_ops;
> +		smp_ops.smp_send_stop = paravirt_nop;
> +	}
>  }
>  
> diff --git a/arch/x86/xen/irq.c b/arch/x86/xen/irq.c
> index 52885c1..edca1c4 100644
> --- a/arch/x86/xen/irq.c
> +++ b/arch/x86/xen/irq.c
> @@ -66,6 +66,9 @@ PV_CALLEE_SAVE_REGS_THUNK(xen_restore_fl);
>  
>  static void xen_irq_disable(void)
>  {
> +	if (xen_hybrid_evtchn_enabled())
> +		asm volatile("cli" : : : "memory");
>   

!!! We have pvops for a reason.  If you want to override irq_disable,
define a new pvop function.

    J
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