[Qemu-devel] [Patch] s390x/kvm: make setting of in-kernel irq routes more efficient

[Qemu-devel] [Patch] s390x/kvm: make setting of in-kernel irq routes more efficient

[Jens Freimann]

When we add new adapter routes we call kvm_irqchip_add_route() for every
virtqueue and in the same step also do the KVM_SET_GSI_ROUTING ioctl.

This is unnecessary costly as the interface allows us to set multiple
routes in one go. Let's first add all routes to the table stored in the
global kvm_state and then do the ioctl to commit the routes to the
in-kernel irqchip.

This saves us several ioctls to the kernel where for each call a list
is reallocated and populated.

Signed-off-by: Jens Freimann <jfrei@linux.vnet.ibm.com>
Reviewed-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
---
 hw/intc/s390_flic_kvm.c | 2 ++
 kvm-all.c               | 1 -
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/hw/intc/s390_flic_kvm.c b/hw/intc/s390_flic_kvm.c
index b471e7a..48714f9 100644
--- a/hw/intc/s390_flic_kvm.c
+++ b/hw/intc/s390_flic_kvm.c
@@ -228,6 +228,8 @@ static int kvm_s390_add_adapter_routes(S390FLICState *fs,
         routes->gsi[i] = ret;
         routes->adapter.ind_offset++;
     }
+    kvm_irqchip_commit_routes(kvm_state);
+
     /* Restore passed-in structure to original state. */
     routes->adapter.ind_offset = ind_offset;
     return 0;
diff --git a/kvm-all.c b/kvm-all.c
index 06e06f2..c6f5128 100644
--- a/kvm-all.c
+++ b/kvm-all.c
@@ -1293,7 +1293,6 @@ int kvm_irqchip_add_adapter_route(KVMState *s, AdapterInfo *adapter)
     kroute.u.adapter.adapter_id = adapter->adapter_id;
 
     kvm_add_routing_entry(s, &kroute);
-    kvm_irqchip_commit_routes(s);
 
     return virq;
 }
-- 
2.3.8

Re: [Qemu-devel] [Patch] s390x/kvm: make setting of in-kernel irq routes more efficient

[Paolo Bonzini]

On 10/08/2015 16:02, Jens Freimann wrote:
> When we add new adapter routes we call kvm_irqchip_add_route() for every
> virtqueue and in the same step also do the KVM_SET_GSI_ROUTING ioctl.
> 
> This is unnecessary costly as the interface allows us to set multiple
> routes in one go. Let's first add all routes to the table stored in the
> global kvm_state and then do the ioctl to commit the routes to the
> in-kernel irqchip.
> 
> This saves us several ioctls to the kernel where for each call a list
> is reallocated and populated.

Acked-by: Paolo Bonzini <pbonzini@redhat.com>

but we should do the same for kvm_irqchip_add_msi_route as well.  I'll
prepare a patch.

Paolo

> Signed-off-by: Jens Freimann <jfrei@linux.vnet.ibm.com>
> Reviewed-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
> ---
>  hw/intc/s390_flic_kvm.c | 2 ++
>  kvm-all.c               | 1 -
>  2 files changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/intc/s390_flic_kvm.c b/hw/intc/s390_flic_kvm.c
> index b471e7a..48714f9 100644
> --- a/hw/intc/s390_flic_kvm.c
> +++ b/hw/intc/s390_flic_kvm.c
> @@ -228,6 +228,8 @@ static int kvm_s390_add_adapter_routes(S390FLICState *fs,
>          routes->gsi[i] = ret;
>          routes->adapter.ind_offset++;
>      }
> +    kvm_irqchip_commit_routes(kvm_state);
> +
>      /* Restore passed-in structure to original state. */
>      routes->adapter.ind_offset = ind_offset;
>      return 0;
> diff --git a/kvm-all.c b/kvm-all.c
> index 06e06f2..c6f5128 100644
> --- a/kvm-all.c
> +++ b/kvm-all.c
> @@ -1293,7 +1293,6 @@ int kvm_irqchip_add_adapter_route(KVMState *s, AdapterInfo *adapter)
>      kroute.u.adapter.adapter_id = adapter->adapter_id;
>  
>      kvm_add_routing_entry(s, &kroute);
> -    kvm_irqchip_commit_routes(s);
>  
>      return virq;
>  }
> -- 2.3.8