Currently, IRQFD on arm still uses the deferred workqueue mechanism to inject interrupts into guest, which will likely lead to a busy context-switching from/to the kworker thread. This overhead is for no purpose (only in my view ...) and will result in an interrupt performance degradation.
Implement kvm_arch_set_irq_inatomic() for arm/arm64 to support direct irqfd MSI injection, by which we can get rid of the annoying latency. As a result, irqfd MSI intensive scenarios (e.g., DPDK with high packet processing workloads) will benefit from it. Signed-off-by: Zenghui Yu <[email protected]> --- It seems that only MSI will follow the IRQFD path, did I miss something? This patch is still under test and sent out for early feedback. If I have any mis-understanding, please fix me up and let me know. Thanks! --- virt/kvm/arm/vgic/trace.h | 22 ++++++++++++++++++++++ virt/kvm/arm/vgic/vgic-irqfd.c | 21 +++++++++++++++++++++ 2 files changed, 43 insertions(+) diff --git a/virt/kvm/arm/vgic/trace.h b/virt/kvm/arm/vgic/trace.h index 55fed77..bc1f4db 100644 --- a/virt/kvm/arm/vgic/trace.h +++ b/virt/kvm/arm/vgic/trace.h @@ -27,6 +27,28 @@ __entry->vcpu_id, __entry->irq, __entry->level) ); +TRACE_EVENT(kvm_arch_set_irq_inatomic, + TP_PROTO(u32 gsi, u32 type, int level, int irq_source_id), + TP_ARGS(gsi, type, level, irq_source_id), + + TP_STRUCT__entry( + __field( u32, gsi ) + __field( u32, type ) + __field( int, level ) + __field( int, irq_source_id ) + ), + + TP_fast_assign( + __entry->gsi = gsi; + __entry->type = type; + __entry->level = level; + __entry->irq_source_id = irq_source_id; + ), + + TP_printk("gsi %u type %u level %d source %d", __entry->gsi, + __entry->type, __entry->level, __entry->irq_source_id) +); + #endif /* _TRACE_VGIC_H */ #undef TRACE_INCLUDE_PATH diff --git a/virt/kvm/arm/vgic/vgic-irqfd.c b/virt/kvm/arm/vgic/vgic-irqfd.c index 99e026d..4cfc3f4 100644 --- a/virt/kvm/arm/vgic/vgic-irqfd.c +++ b/virt/kvm/arm/vgic/vgic-irqfd.c @@ -19,6 +19,7 @@ #include <trace/events/kvm.h> #include <kvm/arm_vgic.h> #include "vgic.h" +#include "trace.h" /** * vgic_irqfd_set_irq: inject the IRQ corresponding to the @@ -105,6 +106,26 @@ int kvm_set_msi(struct kvm_kernel_irq_routing_entry *e, return vgic_its_inject_msi(kvm, &msi); } +/** + * kvm_arch_set_irq_inatomic: fast-path for irqfd injection + * + * Currently only direct MSI injecton is supported. + */ +int kvm_arch_set_irq_inatomic(struct kvm_kernel_irq_routing_entry *e, + struct kvm *kvm, int irq_source_id, int level, + bool line_status) +{ + int ret; + + trace_kvm_arch_set_irq_inatomic(e->gsi, e->type, level, irq_source_id); + + if (unlikely(e->type != KVM_IRQ_ROUTING_MSI)) + return -EWOULDBLOCK; + + ret = kvm_set_msi(e, kvm, irq_source_id, level, line_status); + return ret; +} + int kvm_vgic_setup_default_irq_routing(struct kvm *kvm) { struct kvm_irq_routing_entry *entries; -- 1.8.3.1 _______________________________________________ kvmarm mailing list [email protected] https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
