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Message-ID: <alpine.DEB.2.02.1401281651400.4373@kaball.uk.xensource.com>
Date: Tue, 28 Jan 2014 17:13:55 +0000
From: Stefano Stabellini <stefano.stabellini@...citrix.com>
To: Julien Grall <julien.grall@...aro.org>
CC: <linux-kernel@...r.kernel.org>, <stefano.stabellini@...citrix.com>,
<linux-arm-kernel@...ts.infradead.org>, <konrad.wilk@...cle.com>,
<boris.ostrovsky@...cle.com>, <ian.campbell@...rix.com>,
<xen-devel@...ts.xenproject.org>, <patches@...aro.org>,
<david.vrabel@...rix.com>
Subject: Re: [PATCH] arm/xen: Initialize event channels earlier
On Tue, 28 Jan 2014, Julien Grall wrote:
> Event channels driver needs to be initialized very early. Until now, Xen
> initialization was done after all CPUs was bring up.
>
> We can safely move the initialization to an early initcall.
>
> Also use a cpu notifier to:
> - Register the VCPU when the CPU is prepared
> - Enable event channel IRQ when the CPU is running
>
> Signed-off-by: Julien Grall <julien.grall@...aro.org>
Did you test this patch in Dom0 as well as in DomUs?
> arch/arm/xen/enlighten.c | 84 ++++++++++++++++++++++++++++++----------------
> 1 file changed, 55 insertions(+), 29 deletions(-)
>
> diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
> index 293eeea..39b668e 100644
> --- a/arch/arm/xen/enlighten.c
> +++ b/arch/arm/xen/enlighten.c
> @@ -23,6 +23,7 @@
> #include <linux/of_address.h>
> #include <linux/cpuidle.h>
> #include <linux/cpufreq.h>
> +#include <linux/cpu.h>
>
> #include <linux/mm.h>
>
> @@ -154,12 +155,11 @@ int xen_unmap_domain_mfn_range(struct vm_area_struct *vma,
> }
> EXPORT_SYMBOL_GPL(xen_unmap_domain_mfn_range);
>
> -static void __init xen_percpu_init(void *unused)
> +static void xen_percpu_init(int cpu)
> {
> struct vcpu_register_vcpu_info info;
> struct vcpu_info *vcpup;
> int err;
> - int cpu = get_cpu();
>
> pr_info("Xen: initializing cpu%d\n", cpu);
> vcpup = per_cpu_ptr(xen_vcpu_info, cpu);
> @@ -170,9 +170,11 @@ static void __init xen_percpu_init(void *unused)
> err = HYPERVISOR_vcpu_op(VCPUOP_register_vcpu_info, cpu, &info);
> BUG_ON(err);
> per_cpu(xen_vcpu, cpu) = vcpup;
> +}
>
> +static void xen_interrupt_init(void)
> +{
> enable_percpu_irq(xen_events_irq, 0);
> - put_cpu();
> }
>
> static void xen_restart(enum reboot_mode reboot_mode, const char *cmd)
> @@ -193,6 +195,36 @@ static void xen_power_off(void)
> BUG();
> }
>
> +static irqreturn_t xen_arm_callback(int irq, void *arg)
> +{
> + xen_hvm_evtchn_do_upcall();
> + return IRQ_HANDLED;
> +}
> +
> +static int xen_cpu_notification(struct notifier_block *self,
> + unsigned long action,
> + void *hcpu)
> +{
> + int cpu = (long)hcpu;
> +
> + switch (action) {
> + case CPU_UP_PREPARE:
> + xen_percpu_init(cpu);
> + break;
> + case CPU_STARTING:
> + xen_interrupt_init();
> + break;
Is CPU_STARTING guaranteed to be called on the new cpu only?
If so, why not call both xen_percpu_init and xen_interrupt_init on
CPU_STARTING?
As it stands I think you introduced a subtle change (that might be OK
but I think is unintentional): xen_percpu_init might not be called from
the same cpu as its target anymore.
> + default:
> + break;
> + }
> +
> + return NOTIFY_OK;
> +}
> +
> +static struct notifier_block xen_cpu_notifier = {
> + .notifier_call = xen_cpu_notification,
> +};
> +
> /*
> * see Documentation/devicetree/bindings/arm/xen.txt for the
> * documentation of the Xen Device Tree format.
> @@ -209,6 +241,7 @@ static int __init xen_guest_init(void)
> const char *xen_prefix = "xen,xen-";
> struct resource res;
> phys_addr_t grant_frames;
> + int cpu;
>
> node = of_find_compatible_node(NULL, NULL, "xen,xen");
> if (!node) {
> @@ -281,9 +314,27 @@ static int __init xen_guest_init(void)
> disable_cpuidle();
> disable_cpufreq();
>
> + xen_init_IRQ();
> +
> + if (xen_events_irq < 0)
> + return -ENODEV;
Since you are moving this code to xen_guest_init, you can check for
xen_events_irq earlier on, where we parse the irq from device tree.
> + if (request_percpu_irq(xen_events_irq, xen_arm_callback,
> + "events", &xen_vcpu)) {
> + pr_err("Error request IRQ %d\n", xen_events_irq);
> + return -EINVAL;
> + }
> +
> + cpu = get_cpu();
> + xen_percpu_init(cpu);
> + xen_interrupt_init();
> + put_cpu();
> +
> + register_cpu_notifier(&xen_cpu_notifier);
> +
> return 0;
> }
> -core_initcall(xen_guest_init);
> +early_initcall(xen_guest_init);
>
> static int __init xen_pm_init(void)
> {
> @@ -297,31 +348,6 @@ static int __init xen_pm_init(void)
> }
> late_initcall(xen_pm_init);
>
> -static irqreturn_t xen_arm_callback(int irq, void *arg)
> -{
> - xen_hvm_evtchn_do_upcall();
> - return IRQ_HANDLED;
> -}
> -
> -static int __init xen_init_events(void)
> -{
> - if (!xen_domain() || xen_events_irq < 0)
> - return -ENODEV;
> -
> - xen_init_IRQ();
> -
> - if (request_percpu_irq(xen_events_irq, xen_arm_callback,
> - "events", &xen_vcpu)) {
> - pr_err("Error requesting IRQ %d\n", xen_events_irq);
> - return -EINVAL;
> - }
> -
> - on_each_cpu(xen_percpu_init, NULL, 0);
> -
> - return 0;
> -}
> -postcore_initcall(xen_init_events);
> -
> /* In the hypervisor.S file. */
> EXPORT_SYMBOL_GPL(HYPERVISOR_event_channel_op);
> EXPORT_SYMBOL_GPL(HYPERVISOR_grant_table_op);
> --
> 1.7.10.4
>
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