Re: [PATCH 1/2] xen/x86: Move irq allocation from Xen smp_op.cpu_up()

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Thu, Mar 17, 2016 at 09:33:32AM -0400, Boris Ostrovsky wrote:
> Commit ce0d3c0a6fb1 ("genirq: Revert sparse irq locking around
> __cpu_up() and move it to x86 for now") reverted irq locking
> introduced by commit a89941816726 ("hotplug: Prevent alloc/free
> of irq descriptors during cpu up/down") because of Xen allocating
> irqs in both of its cpu_up ops.
> 
> We can move those allocations into CPU notifiers so that original
> patch can be reinstated.

Original being "hotplug: Prevent alloc/free..." ?

> 
> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
> ---
>  arch/x86/xen/enlighten.c |   53 ++++++++++++++++++++++++++++++++++++++-------
>  arch/x86/xen/smp.c       |   45 +-------------------------------------
>  arch/x86/xen/smp.h       |    3 ++
>  3 files changed, 49 insertions(+), 52 deletions(-)
> 
> diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
> index 2c26108..d1a86db 100644
> --- a/arch/x86/xen/enlighten.c
> +++ b/arch/x86/xen/enlighten.c
> @@ -137,6 +137,8 @@ RESERVE_BRK(shared_info_page_brk, PAGE_SIZE);
>  __read_mostly int xen_have_vector_callback;
>  EXPORT_SYMBOL_GPL(xen_have_vector_callback);
>  
> +static struct notifier_block xen_cpu_notifier;
> +
>  /*
>   * Point at some empty memory to start with. We map the real shared_info
>   * page as soon as fixmap is up and running.
> @@ -1596,6 +1598,7 @@ asmlinkage __visible void __init xen_start_kernel(void)
>  	xen_initial_gdt = &per_cpu(gdt_page, 0);
>  
>  	xen_smp_init();
> +	register_cpu_notifier(&xen_cpu_notifier);
>  
>  #ifdef CONFIG_ACPI_NUMA
>  	/*
> @@ -1783,17 +1786,49 @@ static void __init init_hvm_pv_info(void)
>  	xen_domain_type = XEN_HVM_DOMAIN;
>  }
>  
> -static int xen_hvm_cpu_notify(struct notifier_block *self, unsigned long action,
> -			      void *hcpu)
> +static int xen_cpu_notify(struct notifier_block *self, unsigned long action,
> +			  void *hcpu)
>  {
>  	int cpu = (long)hcpu;
> +	int rc;
> +
>  	switch (action) {
>  	case CPU_UP_PREPARE:
> -		xen_vcpu_setup(cpu);
> -		if (xen_have_vector_callback) {
> -			if (xen_feature(XENFEAT_hvm_safe_pvclock))
> -				xen_setup_timer(cpu);
> +		if (xen_hvm_domain()) {
> +			/*
> +			 * This can happen if CPU was offlined earlier and
> +			 * offlining timed out in common_cpu_die().
> +			 */
> +			if (cpu_report_state(cpu) == CPU_DEAD_FROZEN) {
> +				xen_smp_intr_free(cpu);
> +				xen_uninit_lock_cpu(cpu);
> +			}
> +
> +			xen_vcpu_setup(cpu);
>  		}
> +
> +		if (xen_pv_domain() ||
> +		    (xen_have_vector_callback &&
> +		     xen_feature(XENFEAT_hvm_safe_pvclock)))
> +			xen_setup_timer(cpu);
> +
> +		rc = xen_smp_intr_init(cpu);
> +		if (rc) {
> +			WARN(1, "xen_smp_intr_init() for CPU %d failed: %d\n",
> +			     cpu, rc);
> +			return NOTIFY_BAD;
> +		}
> +
> +		break;
> +	case CPU_ONLINE:
> +		xen_init_lock_cpu(cpu);
> +		break;
> +	case CPU_UP_CANCELED:
> +		xen_smp_intr_free(cpu);

xen_uninit_lock_cpu ?


> +		if (xen_pv_domain() ||
> +		    (xen_have_vector_callback &&
> +		     xen_feature(XENFEAT_hvm_safe_pvclock)))
> +			xen_teardown_timer(cpu);
>  		break;
>  	default:
>  		break;
> @@ -1801,8 +1836,8 @@ static int xen_hvm_cpu_notify(struct notifier_block *self, unsigned long action,
>  	return NOTIFY_OK;
>  }
>  
> -static struct notifier_block xen_hvm_cpu_notifier = {
> -	.notifier_call	= xen_hvm_cpu_notify,
> +static struct notifier_block xen_cpu_notifier = {
> +	.notifier_call	= xen_cpu_notify,
>  };
>  
>  #ifdef CONFIG_KEXEC_CORE
> @@ -1834,7 +1869,7 @@ static void __init xen_hvm_guest_init(void)
>  	if (xen_feature(XENFEAT_hvm_callback_vector))
>  		xen_have_vector_callback = 1;
>  	xen_hvm_smp_init();
> -	register_cpu_notifier(&xen_hvm_cpu_notifier);
> +	register_cpu_notifier(&xen_cpu_notifier);
>  	xen_unplug_emulated_devices();
>  	x86_init.irqs.intr_init = xen_init_IRQ;
>  	xen_hvm_init_time_ops();
> diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
> index 719cf29..09d5cc0 100644
> --- a/arch/x86/xen/smp.c
> +++ b/arch/x86/xen/smp.c
> @@ -115,7 +115,7 @@ asmlinkage __visible void cpu_bringup_and_idle(int cpu)
>  	cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
>  }
>  
> -static void xen_smp_intr_free(unsigned int cpu)
> +void xen_smp_intr_free(unsigned int cpu)
>  {
>  	if (per_cpu(xen_resched_irq, cpu).irq >= 0) {
>  		unbind_from_irqhandler(per_cpu(xen_resched_irq, cpu).irq, NULL);
> @@ -159,7 +159,7 @@ static void xen_smp_intr_free(unsigned int cpu)
>  		per_cpu(xen_pmu_irq, cpu).name = NULL;
>  	}
>  };
> -static int xen_smp_intr_init(unsigned int cpu)
> +int xen_smp_intr_init(unsigned int cpu)
>  {
>  	int rc;
>  	char *resched_name, *callfunc_name, *debug_name, *pmu_name;
> @@ -468,8 +468,6 @@ static int xen_cpu_up(unsigned int cpu, struct task_struct *idle)
>  	common_cpu_up(cpu, idle);
>  
>  	xen_setup_runstate_info(cpu);
> -	xen_setup_timer(cpu);
> -	xen_init_lock_cpu(cpu);
>  
>  	/*
>  	 * PV VCPUs are always successfully taken down (see 'while' loop
> @@ -488,10 +486,6 @@ static int xen_cpu_up(unsigned int cpu, struct task_struct *idle)
>  
>  	xen_pmu_init(cpu);
>  
> -	rc = xen_smp_intr_init(cpu);
> -	if (rc)
> -		return rc;
> -
>  	rc = HYPERVISOR_vcpu_op(VCPUOP_up, cpu, NULL);
>  	BUG_ON(rc);
>  
> @@ -761,47 +755,12 @@ static void __init xen_hvm_smp_prepare_cpus(unsigned int max_cpus)
>  	xen_init_lock_cpu(0);
>  }
>  
> -static int xen_hvm_cpu_up(unsigned int cpu, struct task_struct *tidle)
> -{
> -	int rc;
> -
> -	/*
> -	 * This can happen if CPU was offlined earlier and
> -	 * offlining timed out in common_cpu_die().
> -	 */
> -	if (cpu_report_state(cpu) == CPU_DEAD_FROZEN) {
> -		xen_smp_intr_free(cpu);
> -		xen_uninit_lock_cpu(cpu);
> -	}
> -
> -	/*
> -	 * xen_smp_intr_init() needs to run before native_cpu_up()
> -	 * so that IPI vectors are set up on the booting CPU before
> -	 * it is marked online in native_cpu_up().
> -	*/
> -	rc = xen_smp_intr_init(cpu);
> -	WARN_ON(rc);
> -	if (!rc)
> -		rc =  native_cpu_up(cpu, tidle);
> -
> -	/*
> -	 * We must initialize the slowpath CPU kicker _after_ the native
> -	 * path has executed. If we initialized it before none of the
> -	 * unlocker IPI kicks would reach the booting CPU as the booting
> -	 * CPU had not set itself 'online' in cpu_online_mask. That mask
> -	 * is checked when IPIs are sent (on HVM at least).
> -	 */
> -	xen_init_lock_cpu(cpu);
> -	return rc;
> -}
> -
>  void __init xen_hvm_smp_init(void)
>  {
>  	if (!xen_have_vector_callback)
>  		return;
>  	smp_ops.smp_prepare_cpus = xen_hvm_smp_prepare_cpus;
>  	smp_ops.smp_send_reschedule = xen_smp_send_reschedule;
> -	smp_ops.cpu_up = xen_hvm_cpu_up;
>  	smp_ops.cpu_die = xen_cpu_die;
>  	smp_ops.send_call_func_ipi = xen_smp_send_call_function_ipi;
>  	smp_ops.send_call_func_single_ipi = xen_smp_send_call_function_single_ipi;
> diff --git a/arch/x86/xen/smp.h b/arch/x86/xen/smp.h
> index 963d62a..45faaf3 100644
> --- a/arch/x86/xen/smp.h
> +++ b/arch/x86/xen/smp.h
> @@ -8,6 +8,9 @@ extern void xen_send_IPI_allbutself(int vector);
>  extern void xen_send_IPI_all(int vector);
>  extern void xen_send_IPI_self(int vector);
>  
> +extern int xen_smp_intr_init(unsigned int cpu);
> +extern void xen_smp_intr_free(unsigned int cpu);
> +
>  #ifdef CONFIG_XEN_PVH
>  extern void xen_pvh_early_cpu_init(int cpu, bool entry);
>  #else
> -- 
> 1.7.1
> 

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