On Sun, Jul 29, 2012 at 11:00:58PM +0300, Michael S. Tsirkin wrote:
> I've been looking at adding caching for IRQs so that we don't need to
> scan all VCPUs on each interrupt. One issue I had a problem with, is
> how the cache structure can be used from both a thread (to fill out the
> cache) and interrupt (to actually send if cache is valid).
I do not get this. Cache should be fill out at the time of use.
>
> For now just added a lock field in the cache so we don't need to worry
> about this, and with such a lock in place we don't have to worry about
> RCU as cache can be invalidated simply under this lock.
Cache should be invalidated at the time of use if irq routing changed.
>
> For now this just declares the structure and updates the APIs
> so it's not intended to be applied, but just to give you
> the idea.
>
> Comments, flames wellcome.
>
There is no enough meat to discuss here I am afraid.
> Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
>
> --
>
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 96c158a..3384b39 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -214,11 +214,28 @@ static inline unsigned long kvm_dirty_bitmap_bytes(struct kvm_memory_slot *memsl
> return ALIGN(memslot->npages, BITS_PER_LONG) / 8;
> }
>
> +struct kvm_irq_cache {
> + spinlock_t lock;
> + bool valid;
> + struct kvm_vcpu *dest;
> + /* For now we only cache lapic irqs */
> + struct kvm_lapic_irq irq;
> + /* Protected by kvm->irq_cache_lock */
> + struct list_head list;
Why are you storing them in the list? This should be embedded structure.
> +};
> +
> +int kvm_set_irq_and_cache(struct kvm *kvm, int irq_source_id, u32 irq, int level,
> + struct kvm_irq_cache *cache);
> +int kvm_set_irq_cached(struct kvm *kvm, struct kvm_irq_cache *cache);
> +void kvm_irq_cache_init(struct kvm *kvm, struct kvm_irq_cache *cache);
> +void kvm_irq_cache_cleanup(struct kvm_irq_cache *cache);
> +
> struct kvm_kernel_irq_routing_entry {
> u32 gsi;
> u32 type;
> int (*set)(struct kvm_kernel_irq_routing_entry *e,
> - struct kvm *kvm, int irq_source_id, int level);
> + struct kvm *kvm, int irq_source_id, int level,
> + struct kvm_irq_cache *cache);
> union {
> struct {
> unsigned irqchip;
> @@ -304,6 +321,8 @@ struct kvm {
> struct kvm_irq_routing_table __rcu *irq_routing;
> struct hlist_head mask_notifier_list;
> struct hlist_head irq_ack_notifier_list;
> + struct mutex irq_cache_lock;
> + struct list_head irq_cache_list;
> #endif
>
> #ifdef KVM_ARCH_WANT_MMU_NOTIFIER
> @@ -617,7 +636,8 @@ void kvm_get_intr_delivery_bitmask(struct kvm_ioapic *ioapic,
> #endif
> int kvm_set_irq(struct kvm *kvm, int irq_source_id, u32 irq, int level);
> int kvm_set_msi(struct kvm_kernel_irq_routing_entry *irq_entry, struct kvm *kvm,
> - int irq_source_id, int level);
> + int irq_source_id, int level,
> + struct kvm_irq_cache *cache);
> void kvm_notify_acked_irq(struct kvm *kvm, unsigned irqchip, unsigned pin);
> void kvm_register_irq_ack_notifier(struct kvm *kvm,
> struct kvm_irq_ack_notifier *kian);
> diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
> index 7d7e2aa..9622076 100644
> --- a/virt/kvm/eventfd.c
> +++ b/virt/kvm/eventfd.c
> @@ -138,7 +138,7 @@ irqfd_wakeup(wait_queue_t *wait, unsigned mode, int sync, void *key)
> irq = rcu_dereference(irqfd->irq_entry);
> /* An event has been signaled, inject an interrupt */
> if (irq)
> - kvm_set_msi(irq, kvm, KVM_USERSPACE_IRQ_SOURCE_ID, 1);
> + kvm_set_msi(irq, kvm, KVM_USERSPACE_IRQ_SOURCE_ID, 1, NULL);
> else
> schedule_work(&irqfd->inject);
> rcu_read_unlock();
> diff --git a/virt/kvm/irq_comm.c b/virt/kvm/irq_comm.c
> index 5afb431..d92f3d3 100644
> --- a/virt/kvm/irq_comm.c
> +++ b/virt/kvm/irq_comm.c
> @@ -46,7 +46,8 @@ static inline int kvm_irq_line_state(unsigned long *irq_state,
> }
>
> static int kvm_set_pic_irq(struct kvm_kernel_irq_routing_entry *e,
> - struct kvm *kvm, int irq_source_id, int level)
> + struct kvm *kvm, int irq_source_id, int level,
> + struct kvm_irq_cache *cache)
> {
> #ifdef CONFIG_X86
> struct kvm_pic *pic = pic_irqchip(kvm);
> @@ -59,7 +60,8 @@ static int kvm_set_pic_irq(struct kvm_kernel_irq_routing_entry *e,
> }
>
> static int kvm_set_ioapic_irq(struct kvm_kernel_irq_routing_entry *e,
> - struct kvm *kvm, int irq_source_id, int level)
> + struct kvm *kvm, int irq_source_id, int level,
> + struct kvm_irq_cache *cache)
> {
> struct kvm_ioapic *ioapic = kvm->arch.vioapic;
> level = kvm_irq_line_state(&ioapic->irq_states[e->irqchip.pin],
> @@ -115,7 +117,8 @@ int kvm_irq_delivery_to_apic(struct kvm *kvm, struct kvm_lapic *src,
> }
>
> int kvm_set_msi(struct kvm_kernel_irq_routing_entry *e,
> - struct kvm *kvm, int irq_source_id, int level)
> + struct kvm *kvm, int irq_source_id, int level,
> + struct kvm_irq_cache *cache)
> {
> struct kvm_lapic_irq irq;
>
> @@ -149,7 +152,7 @@ int kvm_send_userspace_msi(struct kvm *kvm, struct kvm_msi *msi)
> route.msi.address_hi = msi->address_hi;
> route.msi.data = msi->data;
>
> - return kvm_set_msi(&route, kvm, KVM_USERSPACE_IRQ_SOURCE_ID, 1);
> + return kvm_set_msi(&route, kvm, KVM_USERSPACE_IRQ_SOURCE_ID, 1, NULL);
> }
>
> /*
> @@ -180,7 +183,7 @@ int kvm_set_irq(struct kvm *kvm, int irq_source_id, u32 irq, int level)
>
> while(i--) {
> int r;
> - r = irq_set[i].set(&irq_set[i], kvm, irq_source_id, level);
> + r = irq_set[i].set(&irq_set[i], kvm, irq_source_id, level, NULL);
> if (r < 0)
> continue;
>
> --
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--
Gleb.
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