From: Sean Christopherson Date: Wed, 10 Jan 2024 00:39:38 +0000 (-0800) Subject: KVM: Add a comment explaining the directed yield pending interrupt logic X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=dafc17dd529a6194e199b837916062090562ff80;p=linux.git 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: Sean Christopherson --- diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 9b92858c8b72a..c0c2fcdabe1b3 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -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))