[Qemu-devel] [PULL 044/103] Add kvm_eventfds_enabled function

["Michael S. Tsirkin" <mst@redhat.com>]

From: Nikolay Nikolaev <n.nikolaev@virtualopensystems.com>

Add a function to check if the eventfd capability is present in KVM in
the host kernel.

Signed-off-by: Antonios Motakis <a.motakis@virtualopensystems.com>
Signed-off-by: Nikolay Nikolaev <n.nikolaev@virtualopensystems.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
---
 include/sysemu/kvm.h | 11 +++++++++++
 kvm-all.c            |  4 ++++
 kvm-stub.c           |  1 +
 3 files changed, 16 insertions(+)

diff --git a/include/sysemu/kvm.h b/include/sysemu/kvm.h
index e79e92c..c4556ad 100644
--- a/include/sysemu/kvm.h
+++ b/include/sysemu/kvm.h
@@ -43,6 +43,7 @@ extern bool kvm_allowed;
 extern bool kvm_kernel_irqchip;
 extern bool kvm_async_interrupts_allowed;
 extern bool kvm_halt_in_kernel_allowed;
+extern bool kvm_eventfds_allowed;
 extern bool kvm_irqfds_allowed;
 extern bool kvm_msi_via_irqfd_allowed;
 extern bool kvm_gsi_routing_allowed;
@@ -83,6 +84,15 @@ extern bool kvm_readonly_mem_allowed;
 #define kvm_halt_in_kernel() (kvm_halt_in_kernel_allowed)
 
 /**
+ * kvm_eventfds_enabled:
+ *
+ * Returns: true if we can use eventfds to receive notifications
+ * from a KVM CPU (ie the kernel supports eventds and we are running
+ * with a configuration where it is meaningful to use them).
+ */
+#define kvm_eventfds_enabled() (kvm_eventfds_allowed)
+
+/**
  * kvm_irqfds_enabled:
  *
  * Returns: true if we can use irqfds to inject interrupts into
@@ -128,6 +138,7 @@ extern bool kvm_readonly_mem_allowed;
 #define kvm_irqchip_in_kernel() (false)
 #define kvm_async_interrupts_enabled() (false)
 #define kvm_halt_in_kernel() (false)
+#define kvm_eventfds_enabled() (false)
 #define kvm_irqfds_enabled() (false)
 #define kvm_msi_via_irqfd_enabled() (false)
 #define kvm_gsi_routing_allowed() (false)
diff --git a/kvm-all.c b/kvm-all.c
index 4e19eff..92f56d8 100644
--- a/kvm-all.c
+++ b/kvm-all.c
@@ -113,6 +113,7 @@ KVMState *kvm_state;
 bool kvm_kernel_irqchip;
 bool kvm_async_interrupts_allowed;
 bool kvm_halt_in_kernel_allowed;
+bool kvm_eventfds_allowed;
 bool kvm_irqfds_allowed;
 bool kvm_msi_via_irqfd_allowed;
 bool kvm_gsi_routing_allowed;
@@ -1541,6 +1542,9 @@ int kvm_init(MachineClass *mc)
         (kvm_check_extension(s, KVM_CAP_READONLY_MEM) > 0);
 #endif
 
+    kvm_eventfds_allowed =
+        (kvm_check_extension(s, KVM_CAP_IOEVENTFD) > 0);
+
     ret = kvm_arch_init(s);
     if (ret < 0) {
         goto err;
diff --git a/kvm-stub.c b/kvm-stub.c
index ac33d86..8e7737c 100644
--- a/kvm-stub.c
+++ b/kvm-stub.c
@@ -22,6 +22,7 @@
 KVMState *kvm_state;
 bool kvm_kernel_irqchip;
 bool kvm_async_interrupts_allowed;
+bool kvm_eventfds_allowed;
 bool kvm_irqfds_allowed;
 bool kvm_msi_via_irqfd_allowed;
 bool kvm_gsi_routing_allowed;
-- 
MST