From 76b25000867111067128fbc33d63cd29fec571d9 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Tue, 21 Dec 2021 10:37:00 -0500 Subject: [PATCH] KVM: VMX: Wake vCPU when delivering posted IRQ even if vCPU == this vCPU 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: 8046fceeb9d7 ("KVM: VMX: Optimize posted-interrupt delivery for timer fastpath") Cc: stable@vger.kernel.org Reported-by: Longpeng (Mike) Signed-off-by: Sean Christopherson Reviewed-by: Maxim Levitsky Message-Id: <20211208015236.1616697-18-seanjc@google.com> Signed-off-by: Paolo Bonzini --- arch/x86/kvm/vmx/vmx.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 5974a88c9d358..0dbf94eb954fd 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -3964,8 +3964,7 @@ static int vmx_deliver_posted_interrupt(struct kvm_vcpu *vcpu, int vector) 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; -- 2.39.5