KVM: arm/arm64: vgic: Stop injecting the MSI occurrence twice

KVM: arm/arm64: vgic: Stop injecting the MSI occurrence twice

BugLink: http://bugs.launchpad.net/bugs/1672544
commit 0bdbf3b071986ba80731203683cf623d5c0cacb1 upstream.

The IRQFD framework calls the architecture dependent function
twice if the corresponding GSI type is edge triggered. For ARM,
the function kvm_set_msi() is getting called twice whenever the
IRQFD receives the event signal. The rest of the code path is
trying to inject the MSI without any validation checks. No need
to call the function vgic_its_inject_msi() second time to avoid
an unnecessary overhead in IRQ queue logic. It also avoids the
possibility of VM seeing the MSI twice.

Simple fix, return -1 if the argument 'level' value is zero.

Reviewed-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Christoffer Dall <cdall@linaro.org>
Signed-off-by: Shanker Donthineni <shankerd@codeaurora.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>