linux-kernel - Re: [v4 1/3] genirq: Introduce irq_set_vcpu_affinity() to target an interrupt to a VCPU

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Message-ID: <555306C9.6040405@linux.intel.com>
Date:	Wed, 13 May 2015 16:09:45 +0800
From:	Jiang Liu <jiang.liu@...ux.intel.com>
To:	Feng Wu <feng.wu@...el.com>, tglx@...utronix.de, mingo@...hat.com,
	hpa@...or.com
CC:	linux-kernel@...r.kernel.org
Subject: Re: [v4 1/3] genirq: Introduce irq_set_vcpu_affinity() to target
 an interrupt to a VCPU

On 2015/4/30 15:06, Feng Wu wrote:
> With Posted-Interrupts support in Intel CPU and IOMMU, an external
> interrupt from assigned-devices could be directly delivered to a
> virtual CPU in a virtual machine. Instead of hacking KVM and Intel
> IOMMU drivers, we propose a platform independent interface to target
> an interrupt to a specific virtual CPU in a virtual machine, or set
> virtual CPU affinity for an interrupt.
> 
> By adopting this new interface and the hierarchy irqdomain, we could
> easily support posted-interrupts on Intel platforms, and also provide
> flexible enough interfaces for other platforms to support similar
> features.
> 
> Here is the usage scenario for this interface:
> Guest update MSI/MSI-X interrupt configuration
>         -->QEMU and KVM handle this
>         -->KVM call this interface (passing posted interrupts descriptor
>            and guest vector)
>         -->irq core will transfer the control to IOMMU
>         -->IOMMU will do the real work of updating IRTE (IRTE has new
>            format for VT-d Posted-Interrupts)

Hi Thomas,
	Any comments or suggestions about this abstraction interface?
Thanks!
Gerry

> 
> Signed-off-by: Jiang Liu <jiang.liu@...ux.intel.com>
> Signed-off-by: Feng Wu <feng.wu@...el.com>
> ---
>  include/linux/irq.h |  4 ++++
>  kernel/irq/chip.c   | 14 ++++++++++++++
>  kernel/irq/manage.c | 20 ++++++++++++++++++++
>  3 files changed, 38 insertions(+)
> 
> diff --git a/include/linux/irq.h b/include/linux/irq.h
> index 62c6901..684c35d 100644
> --- a/include/linux/irq.h
> +++ b/include/linux/irq.h
> @@ -327,6 +327,7 @@ static inline irq_hw_number_t irqd_to_hwirq(struct irq_data *d)
>   * @irq_write_msi_msg:	optional to write message content for MSI
>   * @irq_get_irqchip_state:	return the internal state of an interrupt
>   * @irq_set_irqchip_state:	set the internal state of a interrupt
> + * @irq_set_vcpu_affinity:	optional to target a virtual CPU in a virtual
>   * @flags:		chip specific flags
>   */
>  struct irq_chip {
> @@ -369,6 +370,8 @@ struct irq_chip {
>  	int		(*irq_get_irqchip_state)(struct irq_data *data, enum irqchip_irq_state which, bool *state);
>  	int		(*irq_set_irqchip_state)(struct irq_data *data, enum irqchip_irq_state which, bool state);
>  
> +	int		(*irq_set_vcpu_affinity)(struct irq_data *data, void *vcpu_info);
> +
>  	unsigned long	flags;
>  };
>  
> @@ -422,6 +425,7 @@ extern void irq_cpu_online(void);
>  extern void irq_cpu_offline(void);
>  extern int irq_set_affinity_locked(struct irq_data *data,
>  				   const struct cpumask *cpumask, bool force);
> +extern int irq_set_vcpu_affinity(unsigned int irq, void *vcpu_info);
>  
>  #if defined(CONFIG_SMP) && defined(CONFIG_GENERIC_PENDING_IRQ)
>  void irq_move_irq(struct irq_data *data);
> diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
> index eb9a4ea..55016b2 100644
> --- a/kernel/irq/chip.c
> +++ b/kernel/irq/chip.c
> @@ -950,6 +950,20 @@ int irq_chip_retrigger_hierarchy(struct irq_data *data)
>  }
>  
>  /**
> + * irq_chip_set_vcpu_affinity_parent - Set vcpu affinity on the parent interrupt
> + * @data:	Pointer to interrupt specific data
> + * @dest:	The vcpu affinity information
> + */
> +int irq_chip_set_vcpu_affinity_parent(struct irq_data *data, void *vcpu_info)
> +{
> +	data = data->parent_data;
> +	if (data->chip->irq_set_vcpu_affinity)
> +		return data->chip->irq_set_vcpu_affinity(data, vcpu_info);
> +
> +	return -ENOSYS;
> +}
> +
> +/**
>   * irq_chip_set_wake_parent - Set/reset wake-up on the parent interrupt
>   * @data:	Pointer to interrupt specific data
>   * @on:		Whether to set or reset the wake-up capability of this irq
> diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
> index e68932b..5e09bc2 100644
> --- a/kernel/irq/manage.c
> +++ b/kernel/irq/manage.c
> @@ -256,6 +256,26 @@ int irq_set_affinity_hint(unsigned int irq, const struct cpumask *m)
>  }
>  EXPORT_SYMBOL_GPL(irq_set_affinity_hint);
>  
> +int irq_set_vcpu_affinity(unsigned int irq, void *vcpu_info)
> +{
> +	struct irq_desc *desc = irq_to_desc(irq);
> +	struct irq_chip *chip;
> +	unsigned long flags;
> +	int ret = -ENOSYS;
> +
> +	if (!desc)
> +		return -EINVAL;
> +
> +	raw_spin_lock_irqsave(&desc->lock, flags);
> +	chip = desc->irq_data.chip;
> +	if (chip && chip->irq_set_vcpu_affinity)
> +		ret = chip->irq_set_vcpu_affinity(irq_desc_get_irq_data(desc),
> +						  vcpu_info);
> +	raw_spin_unlock_irqrestore(&desc->lock, flags);
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(irq_set_vcpu_affinity);
> +
>  static void irq_affinity_notify(struct work_struct *work)
>  {
>  	struct irq_affinity_notify *notify =
> 
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