KVM: x86/xen: Advertise and document KVM_XEN_HVM_CONFIG_EVTCHN_SEND
At the end of the patch series adding this batch of event channel
acceleration features, finally add the feature bit which advertises
them and document it all.
For SCHEDOP_poll we need to wake a polling vCPU when a given port
is triggered, even when it's masked — and we want to implement that
in the kernel, for efficiency. So we want the kernel to know that it
has sole ownership of event channel delivery. Thus, we allow
userspace to make the 'promise' by setting the corresponding feature
bit in its KVM_XEN_HVM_CONFIG call. As we implement SCHEDOP_poll
bypass later, we will do so only if that promise has been made by
userspace.
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20220303154127.202856-16-dwmw2@infradead.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 3d7b65f..1a7d1b5 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4276,7 +4276,8 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
r = KVM_XEN_HVM_CONFIG_HYPERCALL_MSR |
KVM_XEN_HVM_CONFIG_INTERCEPT_HCALL |
KVM_XEN_HVM_CONFIG_SHARED_INFO |
- KVM_XEN_HVM_CONFIG_EVTCHN_2LEVEL;
+ KVM_XEN_HVM_CONFIG_EVTCHN_2LEVEL |
+ KVM_XEN_HVM_CONFIG_EVTCHN_SEND;
if (sched_info_on())
r |= KVM_XEN_HVM_CONFIG_RUNSTATE;
break;
