On Tue, Sep 17, 2013 at 07:18:40PM +1000, Paul Mackerras wrote:
> This implements a simple way to express the case of IRQ routing where
> there is one in-kernel PIC and the system interrupts (GSIs) are routed
> 1-1 to the corresponding pins of the PIC. This is expressed by having
> kvm->irq_routing == NULL with a skeleton irq routing entry in the new
> kvm->default_irq_route field.
>
> This provides a convenient way to provide backwards compatibility when
> adding IRQ routing capability to an existing in-kernel PIC, such as the
> XICS emulation on powerpc.
>
Why not create simple 1-1 irq routing table? It will take a little bit
more memory, but there will be no need for kvm->irq_routing == NULL
special handling.
> Signed-off-by: Paul Mackerras <pau...@samba.org>
> ---
> include/linux/kvm_host.h | 1 +
> virt/kvm/eventfd.c | 4 ++++
> virt/kvm/irqchip.c | 23 ++++++++++++++++++++---
> 3 files changed, 25 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 749bdb1..609f587 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -394,6 +394,7 @@ struct kvm {
> * if configured, irqfds.lock.
> */
> struct kvm_irq_routing_table __rcu *irq_routing;
> + struct kvm_kernel_irq_routing_entry default_irq_route;
> struct hlist_head mask_notifier_list;
> struct hlist_head irq_ack_notifier_list;
> #endif
> diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
> index abe4d60..7010cb3 100644
> --- a/virt/kvm/eventfd.c
> +++ b/virt/kvm/eventfd.c
> @@ -272,6 +272,10 @@ static void irqfd_update(struct kvm *kvm, struct _irqfd
> *irqfd,
> {
> struct kvm_kernel_irq_routing_entry *e;
>
> + if (!irq_rt) {
> + rcu_assign_pointer(irqfd->irq_entry, NULL);
> + return;
> + }
> if (irqfd->gsi >= irq_rt->nr_rt_entries) {
> rcu_assign_pointer(irqfd->irq_entry, NULL);
> return;
> diff --git a/virt/kvm/irqchip.c b/virt/kvm/irqchip.c
> index 20dc9e4..ebc2941 100644
> --- a/virt/kvm/irqchip.c
> +++ b/virt/kvm/irqchip.c
> @@ -30,13 +30,24 @@
> #include <trace/events/kvm.h>
> #include "irq.h"
>
> +static inline int pin_to_gsi(struct kvm *kvm, unsigned irqchip, unsigned pin)
> +{
> + struct kvm_irq_routing_table *rt;
> + int gsi = pin;
> +
> + rt = rcu_dereference(kvm->irq_routing);
> + if (rt)
> + gsi = rt->chip[irqchip][pin];
> + return gsi;
> +}
> +
> bool kvm_irq_has_notifier(struct kvm *kvm, unsigned irqchip, unsigned pin)
> {
> struct kvm_irq_ack_notifier *kian;
> int gsi;
>
> rcu_read_lock();
> - gsi = rcu_dereference(kvm->irq_routing)->chip[irqchip][pin];
> + gsi = pin_to_gsi(kvm, irqchip, pin);
> if (gsi != -1)
> hlist_for_each_entry_rcu(kian, &kvm->irq_ack_notifier_list,
> link)
> @@ -59,7 +70,7 @@ void kvm_notify_acked_irq(struct kvm *kvm, unsigned
> irqchip, unsigned pin)
> trace_kvm_ack_irq(irqchip, pin);
>
> rcu_read_lock();
> - gsi = rcu_dereference(kvm->irq_routing)->chip[irqchip][pin];
> + gsi = pin_to_gsi(kvm, irqchip, pin);
> if (gsi != -1)
> hlist_for_each_entry_rcu(kian, &kvm->irq_ack_notifier_list,
> link)
> @@ -126,7 +137,13 @@ int kvm_set_irq(struct kvm *kvm, int irq_source_id, u32
> irq, int level,
> */
> rcu_read_lock();
> irq_rt = rcu_dereference(kvm->irq_routing);
> - if (irq < irq_rt->nr_rt_entries)
> + if (!irq_rt) {
> + if (kvm->default_irq_route.set) {
> + irq_set[i] = kvm->default_irq_route;
> + irq_set[i].gsi = irq;
> + irq_set[i++].irqchip.pin = irq;
> + }
> + } else if (irq < irq_rt->nr_rt_entries)
> hlist_for_each_entry(e, &irq_rt->map[irq], link)
> irq_set[i++] = *e;
> rcu_read_unlock();
> --
> 1.8.4.rc3
>
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Gleb.
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