diff mbox series

[4/4] KVM: Add a comment explaining the directed yield pending interrupt logic

Message ID 20240110003938.490206-5-seanjc@google.com (mailing list archive)
State New, archived
Headers show
Series KVM: Clean up "preempted in-kernel" logic | expand

Commit Message

Sean Christopherson Jan. 10, 2024, 12:39 a.m. UTC 
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.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 virt/kvm/kvm_main.c | 7 +++++++
 1 file changed, 7 insertions(+)
diff mbox series

Patch

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 6326852bfb3d..4a9e7513c585 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -4089,6 +4089,13 @@  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))