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

[Sheng Yang <sheng@linux.intel.com>]

On Tuesday 09 March 2010 06:16:30 Jeremy Fitzhardinge wrote:
> On 03/04/2010 10:07 PM, Sheng Yang wrote:
> > We mapped each IOAPIC pin to a VIRQ, so that we can deliver interrupt
> > through these VIRQs.
> >
> > We used X86_PLATFORM_IPI_VECTOR as the notification vector for hypervisor
> > to notify guest about the event.
> >
> > The patch also enabled SMP support, then we can support IPI through
> > evtchn as well.
> >
> > When this feature is enabled, we would relay on Xen PV timer for
> > clockevent, rather than other hardware emulated ones.
> >
> > Then we don't use IOAPIC/LAPIC, eliminated the overhead brought by
> > unnecessary VMExit caused by LAPIC.
> >
> > Signed-off-by: Sheng Yang<sheng@linux.intel.com>
> > ---
> >   arch/x86/xen/enlighten.c    |    6 ++--
> >   arch/x86/xen/hvmpv.c        |   59 +++++++++++++++++++++++++++++++++
> >   arch/x86/xen/irq.c          |   28 ++++++++++++++++
> >   arch/x86/xen/smp.c          |   76
> > ++++++++++++++++++++++++++++++++++++++++-- arch/x86/xen/xen-ops.h      | 
> >  16 +++++++++
> >   drivers/xen/events.c        |   74
> > ++++++++++++++++++++++++++++++++++++++--- include/xen/events.h        |  
> >  4 ++
> >   include/xen/hvm.h           |    5 +++
> >   include/xen/interface/xen.h |    6 +++-
> >   9 files changed, 260 insertions(+), 14 deletions(-)
> >
> > diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
> > index 36daccb..2d60e70 100644
> > --- a/arch/x86/xen/enlighten.c
> > +++ b/arch/x86/xen/enlighten.c
> > @@ -717,7 +717,7 @@ static u32 xen_safe_apic_wait_icr_idle(void)
> >           return 0;
> >   }
> >
> > -static void set_xen_basic_apic_ops(void)
> > +void xen_set_basic_apic_ops(void)
> >   {
> >   	apic->read = xen_apic_read;
> >   	apic->write = xen_apic_write;
> > @@ -1026,7 +1026,7 @@ static void xen_crash_shutdown(struct pt_regs
> > *regs) xen_reboot(SHUTDOWN_crash);
> >   }
> >
> > -static const struct machine_ops __initdata xen_machine_ops = {
> > +const struct machine_ops __initdata xen_machine_ops = {
> >   	.restart = xen_restart,
> >   	.halt = xen_machine_halt,
> >   	.power_off = xen_machine_halt,
> > @@ -1116,7 +1116,7 @@ asmlinkage void __init xen_start_kernel(void)
> >   	/*
> >   	 * set up the basic apic ops.
> >   	 */
> > -	set_xen_basic_apic_ops();
> > +	xen_set_basic_apic_ops();
> >   #endif
> >
> >   	if (xen_feature(XENFEAT_mmu_pt_update_preserve_ad)) {
> > diff --git a/arch/x86/xen/hvmpv.c b/arch/x86/xen/hvmpv.c
> > index 305dcca..673b036 100644
> > --- a/arch/x86/xen/hvmpv.c
> > +++ b/arch/x86/xen/hvmpv.c
> > @@ -17,6 +17,7 @@
> >   #include<xen/interface/version.h>
> >   #include<xen/interface/memory.h>
> >
> > +#include<asm/reboot.h>
> >   #include<asm/xen/cpuid.h>
> >   #include<asm/xen/hypercall.h>
> >   #include<asm/xen/hypervisor.h>
> > @@ -44,6 +45,8 @@ static void __init xen_hvm_pv_banner(void)
> >   	printk(KERN_INFO "Xen version: %d.%d%s\n",
> >   		version>>  16, version&  0xffff, extra.extraversion);
> >   	printk(KERN_INFO "PV feature: PV clocksource enabled\n");
> > +	if (xen_hvm_pv_evtchn_enabled())
> > +		printk(KERN_INFO "PV feature: Event channel enabled\n");
> >   }
> >
> >   static int __init xen_para_available(void)
> > @@ -83,6 +86,9 @@ static int __init init_hvm_pv_info(void)
> >   	if (!(edx&  XEN_CPUID_FEAT2_HVM_PV))
> >   		return -ENODEV;
> >
> > +	if (edx&  XEN_CPUID_FEAT2_HVM_PV_EVTCHN)
> > +		xen_hvm_pv_features |= XEN_HVM_PV_EVTCHN_ENABLED;
> > +
> >   	if (pages<  1)
> >   		return -ENODEV;
> >
> > @@ -127,9 +133,35 @@ static void __init init_pv_clocksource(void)
> >   	xen_register_clocksource();
> >   }
> >
> > +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_hvm_pv_evtchn_intr(void)
> > +{
> > +	per_cpu(irq_count, smp_processor_id())++;
> > +	xen_hvm_evtchn_do_upcall(get_irq_regs());
> > +	per_cpu(irq_count, smp_processor_id())--;
> > +}
> > +
> > +#ifdef CONFIG_X86_LOCAL_APIC
> > +static void xen_hvm_pv_evtchn_apic_write(u32 reg, u32 val)
> > +{
> > +	/* The only one reached here should be EOI */
> > +	WARN_ON(reg != APIC_EOI);
> > +}
> > +#endif
> > +
> >   void __init xen_guest_init(void)
> >   {
> >   	int r;
> > +	uint64_t callback_via;
> >
> >   	/* Ensure the we won't confused with others */
> >   	if (xen_domain())
> > @@ -152,4 +184,31 @@ void __init xen_guest_init(void)
> >   	init_pv_clocksource();
> >
> >   	xen_domain_type = XEN_HVM_DOMAIN;
> > +
> > +	if (xen_hvm_pv_evtchn_enabled()) {
> > +		xen_hvm_pv_init_irq_ops();
> > +
> > +		x86_init.timers.timer_init = xen_time_init;
> > +		x86_init.timers.setup_percpu_clockev = x86_init_noop;
> > +		x86_cpuinit.setup_percpu_clockev = x86_init_noop;
> > +
> > +		pv_apic_ops.startup_ipi_hook = paravirt_nop;
> > +#ifdef CONFIG_X86_LOCAL_APIC
> > +		/*
> > +		 * set up the basic apic ops.
> > +		 */
> > +		xen_set_basic_apic_ops();
> > +		apic->write = xen_hvm_pv_evtchn_apic_write;
> > +#endif
> > +
> > +		callback_via = HVM_CALLBACK_VECTOR(X86_PLATFORM_IPI_VECTOR);
> > +		set_callback_via(callback_via);
> > +
> > +		x86_platform_ipi_callback = do_hvm_pv_evtchn_intr;
> > +
> > +		disable_acpi();
> > +
> > +		xen_hvm_pv_smp_init();
> > +		machine_ops = xen_machine_ops;
> > +	}
> >   }
> > diff --git a/arch/x86/xen/irq.c b/arch/x86/xen/irq.c
> > index 9d30105..e325640 100644
> > --- a/arch/x86/xen/irq.c
> > +++ b/arch/x86/xen/irq.c
> > @@ -2,6 +2,7 @@
> >
> >   #include<asm/x86_init.h>
> >
> > +#include<xen/xen.h>
> >   #include<xen/interface/xen.h>
> >   #include<xen/interface/sched.h>
> >   #include<xen/interface/vcpu.h>
> > @@ -131,3 +132,30 @@ void __init xen_init_irq_ops()
> >   	pv_irq_ops = xen_irq_ops;
> >   	x86_init.irqs.intr_init = xen_init_IRQ;
> >   }
> > +
> > +#ifdef CONFIG_XEN_HVM_PV
> > +static void xen_hvm_pv_evtchn_disable(void)
> > +{
> > +	native_irq_disable();
> > +	xen_irq_disable();
> > +}
> > +PV_CALLEE_SAVE_REGS_THUNK(xen_hvm_pv_evtchn_disable);
> > +
> > +static void xen_hvm_pv_evtchn_enable(void)
> > +{
> > +	native_irq_enable();
> > +	xen_irq_enable();
> > +}
> 
> Why is it necessary to disable both the event mask and eflags.IF?
> Surely IF is enough?
> 
> If it is necessary here, why not for save/restore flags?

Yes, you are right.

IF should be enough.

Update this patch alone, or whole series again? (notice you were replying to 
the old version...)

-- 
regards
Yang, Sheng