This is a note to let you know that I've just added the patch titled KVM: VMX: Wake vCPU when delivering posted IRQ even if vCPU == this vCPU to the 5.10-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: kvm-vmx-wake-vcpu-when-delivering-posted-irq-even-if-vcpu-this-vcpu.patch and it can be found in the queue-5.10 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From fdba608f15e2427419997b0898750a49a735afcb Mon Sep 17 00:00:00 2001 From: Sean Christopherson <seanjc@xxxxxxxxxx> Date: Tue, 21 Dec 2021 10:37:00 -0500 Subject: KVM: VMX: Wake vCPU when delivering posted IRQ even if vCPU == this vCPU From: Sean Christopherson <seanjc@xxxxxxxxxx> 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@xxxxxxxxxxxxxxx Reported-by: Longpeng (Mike) <longpeng2@xxxxxxxxxx> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx> Reviewed-by: Maxim Levitsky <mlevitsk@xxxxxxxxxx> Message-Id: <20211208015236.1616697-18-seanjc@xxxxxxxxxx> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- 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 @@ -4007,8 +4007,7 @@ 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; Patches currently in stable-queue which might be from seanjc@xxxxxxxxxx are queue-5.10/kvm-vmx-wake-vcpu-when-delivering-posted-irq-even-if-vcpu-this-vcpu.patch