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    Subject[v4 1/3] genirq: Introduce irq_set_vcpu_affinity() to target an interrupt to a VCPU
    Date
    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)

    Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
    Signed-off-by: Feng Wu <feng.wu@intel.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 =
    --
    2.1.0


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