From: Sean Christopherson seanjc@google.com
commit fdba608f15e2427419997b0898750a49a735afcb upstream.
Drop a check that guards triggering a posted interrupt on the currently running vCPU, and more importantly guards waking the target vCPU if triggering a posted interrupt fails because the vCPU isn't IN_GUEST_MODE. If a vIRQ is delivered from asynchronous context, the target vCPU can be the currently running vCPU and can also be blocking, in which case skipping kvm_vcpu_wake_up() is effectively dropping what is supposed to be a wake event for the vCPU.
The "do nothing" logic when "vcpu == running_vcpu" mostly works only because the majority of calls to ->deliver_posted_interrupt(), especially when using posted interrupts, come from synchronous KVM context. But if a device is exposed to the guest using vfio-pci passthrough, the VFIO IRQ and vCPU are bound to the same pCPU, and the IRQ is _not_ configured to use posted interrupts, wake events from the device will be delivered to KVM from IRQ context, e.g.
vfio_msihandler() | |-> eventfd_signal() | |-> ... | |-> irqfd_wakeup() | |->kvm_arch_set_irq_inatomic() | |-> kvm_irq_delivery_to_apic_fast() | |-> kvm_apic_set_irq()
This also aligns the non-nested and nested usage of triggering posted interrupts, and will allow for additional cleanups.
Fixes: 379a3c8ee444 ("KVM: VMX: Optimize posted-interrupt delivery for timer fastpath") Cc: stable@vger.kernel.org Reported-by: Longpeng (Mike) longpeng2@huawei.com Signed-off-by: Sean Christopherson seanjc@google.com Reviewed-by: Maxim Levitsky mlevitsk@redhat.com Message-Id: 20211208015236.1616697-18-seanjc@google.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/kvm/vmx/vmx.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)
--- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -3971,8 +3971,7 @@ static int vmx_deliver_posted_interrupt( if (pi_test_and_set_on(&vmx->pi_desc)) return 0;
- if (vcpu != kvm_get_running_vcpu() && - !kvm_vcpu_trigger_posted_interrupt(vcpu, false)) + if (!kvm_vcpu_trigger_posted_interrupt(vcpu, false)) kvm_vcpu_kick(vcpu);
return 0;