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

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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 <seanjc@google.com>
This commit is contained in:
Sean Christopherson 2024-01-09 16:39:38 -08:00
parent 322d79f1db
commit dafc17dd52
1 changed files with 7 additions and 0 deletions
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7
virt/kvm/kvm_main.c
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@ -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))