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Message-ID: <4B95773E.1090608@goop.org>
Date: Mon, 08 Mar 2010 14:16:30 -0800
From: Jeremy Fitzhardinge <jeremy@...p.org>
To: Sheng Yang <sheng@...ux.intel.com>
CC: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>,
Ingo Molnar <mingo@...e.hu>,
Ian Pratt <Ian.Pratt@...citrix.com>,
xen-devel <xen-devel@...ts.xensource.com>,
Ian Campbell <Ian.Campbell@...rix.com>,
linux-kernel@...r.kernel.org
Subject: Re: [Xen-devel] [PATCH 7/7] xen: Enable event channel of PV extension
of HVM
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@...ux.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?
J
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