On Mon, Jun 11, 2012 at 02:19:22PM +0300, Michael S. Tsirkin wrote:
> We do not want a potential broadcast to all VCPUs to run in
> a host IRQ handler. Implement an API that sends an MSI
> interrupt but only if it's safe from interrupt context,
> that is if it is a unicast.
>
We will still iterate over all vcpus, we may as well deliver to them. Or
you want to avoid a lot of vcpu kicks?
> Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
> ---
> include/linux/kvm_host.h | 2 ++
> virt/kvm/irq_comm.c | 37 ++++++++++++++++++++++++++++++++-----
> 2 files changed, 34 insertions(+), 5 deletions(-)
>
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index c446435..ddb476a 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -618,6 +618,8 @@ void kvm_get_intr_delivery_bitmask(struct kvm_ioapic *ioapic,
> 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 kvm_set_msi_inatomic(struct kvm_kernel_irq_routing_entry *irq_entry,
> + struct kvm *kvm);
> 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/irq_comm.c b/virt/kvm/irq_comm.c
> index 5afb431..3395e03 100644
> --- a/virt/kvm/irq_comm.c
> +++ b/virt/kvm/irq_comm.c
> @@ -114,13 +114,20 @@ int kvm_irq_delivery_to_apic(struct kvm *kvm, struct kvm_lapic *src,
> return r;
> }
>
> -int kvm_set_msi(struct kvm_kernel_irq_routing_entry *e,
> - struct kvm *kvm, int irq_source_id, int level)
> +static bool kvm_msi_is_multicast(unsigned dest, int dest_mode)
> {
> - struct kvm_lapic_irq irq;
> + if (dest_mode == 0)
> + /* Physical mode. */
> + return dest == 0xff;
> + else
> + /* Logical mode. */
> + return dest & (dest - 1);
> +}
>
> - if (!level)
> - return -1;
> +static int __kvm_set_msi(struct kvm_kernel_irq_routing_entry *e,
> + struct kvm *kvm, bool noblock)
> +{
> + struct kvm_lapic_irq irq;
>
> trace_kvm_msi_set_irq(e->msi.address_lo, e->msi.data);
>
> @@ -134,10 +141,30 @@ int kvm_set_msi(struct kvm_kernel_irq_routing_entry *e,
> irq.level = 1;
> irq.shorthand = 0;
>
> + /* Multicast MSI doesn't really block but might take a long time. */
> + if (unlikely(noblock && kvm_msi_is_multicast(irq.dest_id,
> + irq.delivery_mode)))
delivery_mode? Should be dest_mode. But you probably need to check that
delivery_mode is not ExtINT either.
> + return -EWOULDBLOCK;
> +
> /* TODO Deal with RH bit of MSI message address */
> return kvm_irq_delivery_to_apic(kvm, NULL, &irq);
> }
>
> +int kvm_set_msi_inatomic(struct kvm_kernel_irq_routing_entry *e,
> + struct kvm *kvm)
> +{
> + return __kvm_set_msi(e, kvm, true);
> +}
> +
> +int kvm_set_msi(struct kvm_kernel_irq_routing_entry *e,
> + struct kvm *kvm, int irq_source_id, int level)
> +{
> + if (unlikely(!level))
> + return -1;
> +
> + return __kvm_set_msi(e, kvm, false);
> +}
> +
> int kvm_send_userspace_msi(struct kvm *kvm, struct kvm_msi *msi)
> {
> struct kvm_kernel_irq_routing_entry route;
> --
> MST
>
> --
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--
Gleb.
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