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Message-ID: <20120717101435.GE7949@redhat.com>
Date: Tue, 17 Jul 2012 13:14:35 +0300
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Alex Williamson <alex.williamson@...hat.com>
Cc: avi@...hat.com, gleb@...hat.com, kvm@...r.kernel.org,
linux-kernel@...r.kernel.org, jan.kiszka@...mens.com
Subject: Re: [PATCH v5 3/4] kvm: Create kvm_clear_irq()
On Mon, Jul 16, 2012 at 02:34:03PM -0600, Alex Williamson wrote:
> This is an alternative to kvm_set_irq(,,,0) which returns the previous
> assertion state of the interrupt and does nothing if it isn't changed.
>
> Signed-off-by: Alex Williamson <alex.williamson@...hat.com>
> ---
>
> include/linux/kvm_host.h | 3 ++
> virt/kvm/irq_comm.c | 78 ++++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 81 insertions(+)
>
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index a7661c0..6c168f1 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -219,6 +219,8 @@ struct kvm_kernel_irq_routing_entry {
> u32 type;
> int (*set)(struct kvm_kernel_irq_routing_entry *e,
> struct kvm *kvm, int irq_source_id, int level);
> + int (*clear)(struct kvm_kernel_irq_routing_entry *e,
> + struct kvm *kvm, int irq_source_id);
> union {
> struct {
> unsigned irqchip;
> @@ -629,6 +631,7 @@ void kvm_get_intr_delivery_bitmask(struct kvm_ioapic *ioapic,
> unsigned long *deliver_bitmask);
> #endif
> int kvm_set_irq(struct kvm *kvm, int irq_source_id, u32 irq, int level);
> +int kvm_clear_irq(struct kvm *kvm, int irq_source_id, u32 irq);
> int kvm_set_msi(struct kvm_kernel_irq_routing_entry *irq_entry, struct kvm *kvm,
> int irq_source_id, int level);
> void kvm_notify_acked_irq(struct kvm *kvm, unsigned irqchip, unsigned pin);
> diff --git a/virt/kvm/irq_comm.c b/virt/kvm/irq_comm.c
> index 5afb431..76e8f22 100644
> --- a/virt/kvm/irq_comm.c
> +++ b/virt/kvm/irq_comm.c
> @@ -68,6 +68,42 @@ static int kvm_set_ioapic_irq(struct kvm_kernel_irq_routing_entry *e,
> return kvm_ioapic_set_irq(ioapic, e->irqchip.pin, level);
> }
>
> +static inline int kvm_clear_irq_line_state(unsigned long *irq_state,
> + int irq_source_id)
> +{
> + return !!test_and_clear_bit(irq_source_id, irq_state);
> +}
> +
> +static int kvm_clear_pic_irq(struct kvm_kernel_irq_routing_entry *e,
> + struct kvm *kvm, int irq_source_id)
> +{
> +#ifdef CONFIG_X86
> + struct kvm_pic *pic = pic_irqchip(kvm);
> + int level = kvm_clear_irq_line_state(&pic->irq_states[e->irqchip.pin],
> + irq_source_id);
> + if (level)
> + kvm_pic_set_irq(pic, e->irqchip.pin,
> + !!pic->irq_states[e->irqchip.pin]);
> + return level;
I think I begin to understand: if (level) checks it was previously set,
and then we clear if needed? I think it's worthwhile to rename
level to orig_level and rewrite as:
if (orig_level && !pic->irq_states[e->irqchip.pin])
kvm_pic_set_irq(pic, e->irqchip.pin, 0);
This both makes the logic clear without need for comments and
saves some cycles on pic in case nothing actually changed.
> +#else
> + return -1;
> +#endif
> +}
> +
> +static int kvm_clear_ioapic_irq(struct kvm_kernel_irq_routing_entry *e,
> + struct kvm *kvm, int irq_source_id)
> +{
> + struct kvm_ioapic *ioapic = kvm->arch.vioapic;
> + int level;
> +
> + level = kvm_clear_irq_line_state(&ioapic->irq_states[e->irqchip.pin],
> + irq_source_id);
> + if (level)
> + kvm_ioapic_set_irq(ioapic, e->irqchip.pin,
> + !!ioapic->irq_states[e->irqchip.pin]);
> + return level;
> +}
> +
> inline static bool kvm_is_dm_lowest_prio(struct kvm_lapic_irq *irq)
> {
> #ifdef CONFIG_IA64
> @@ -190,6 +226,45 @@ int kvm_set_irq(struct kvm *kvm, int irq_source_id, u32 irq, int level)
> return ret;
> }
>
> +/*
> + * Return value:
> + * < 0 Error
> + * = 0 Interrupt was not set, did nothing
> + * > 0 Interrupt was pending, cleared
> + */
> +int kvm_clear_irq(struct kvm *kvm, int irq_source_id, u32 irq)
> +{
> + struct kvm_kernel_irq_routing_entry *e, irq_set[KVM_NR_IRQCHIPS];
> + int ret = -EINVAL, i = 0;
> + struct kvm_irq_routing_table *irq_rt;
> + struct hlist_node *n;
> +
> + /* Not possible to detect if the guest uses the PIC or the
> + * IOAPIC. So clear the bit in both. The guest will ignore
> + * writes to the unused one.
> + */
> + rcu_read_lock();
> + irq_rt = rcu_dereference(kvm->irq_routing);
> + if (irq < irq_rt->nr_rt_entries)
> + hlist_for_each_entry(e, n, &irq_rt->map[irq], link)
> + irq_set[i++] = *e;
> + rcu_read_unlock();
> +
> + while (i--) {
> + int r = -EINVAL;
> +
> + if (irq_set[i].clear)
> + r = irq_set[i].clear(&irq_set[i], kvm, irq_source_id);
> +
> + if (r < 0)
> + continue;
> +
> + ret = r + ((ret < 0) ? 0 : ret);
> + }
> +
> + return ret;
> +}
> +
> void kvm_notify_acked_irq(struct kvm *kvm, unsigned irqchip, unsigned pin)
> {
> struct kvm_irq_ack_notifier *kian;
> @@ -344,16 +419,19 @@ static int setup_routing_entry(struct kvm_irq_routing_table *rt,
> switch (ue->u.irqchip.irqchip) {
> case KVM_IRQCHIP_PIC_MASTER:
> e->set = kvm_set_pic_irq;
> + e->clear = kvm_clear_pic_irq;
> max_pin = 16;
> break;
> case KVM_IRQCHIP_PIC_SLAVE:
> e->set = kvm_set_pic_irq;
> + e->clear = kvm_clear_pic_irq;
> max_pin = 16;
> delta = 8;
> break;
> case KVM_IRQCHIP_IOAPIC:
> max_pin = KVM_IOAPIC_NUM_PINS;
> e->set = kvm_set_ioapic_irq;
> + e->clear = kvm_clear_ioapic_irq;
> break;
> default:
> goto out;
--
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