Commit dafc17dd authored by Sean Christopherson's avatar Sean Christopherson
Browse files

KVM: Add a comment explaining the directed yield pending interrupt logic 

Add a comment to explain why KVM treats vCPUs with pending interrupts as
in-kernel when a vCPU wants to yield to a vCPU that was preempted while
running in kernel mode.

Link: https://lore.kernel.org/r/20240110003938.490206-5-seanjc@google.com


Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
parent 322d79f1

virt/kvm/kvm_main.c

+7 −0
Original line number Diff line number Diff line
@@ -4090,6 +4090,13 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me, bool yield_to_kernel_mode) 
				continue;

			if (kvm_vcpu_is_blocking(vcpu) && !vcpu_dy_runnable(vcpu))

				continue;



			/*

			 * Treat the target vCPU as being in-kernel if it has a

			 * pending interrupt, as the vCPU trying to yield may

			 * be spinning waiting on IPI delivery, i.e. the target

			 * vCPU is in-kernel for the purposes of directed yield.

			 */

			if (READ_ONCE(vcpu->preempted) && yield_to_kernel_mode &&

			    !kvm_arch_dy_has_pending_interrupt(vcpu) &&

			    !kvm_arch_vcpu_preempted_in_kernel(vcpu))