KVM: SVM: Add a comment to explain why avic_vcpu_blocking() ignores IRQ blocking

		return;

	/*

        * Unload the AVIC when the vCPU is about to block, _before_

        * the vCPU actually blocks.

	 * Unload the AVIC when the vCPU is about to block, _before_ the vCPU

	 * actually blocks.

	 *

        * Any IRQs that arrive before IsRunning=0 will not cause an

        * incomplete IPI vmexit on the source, therefore vIRR will also

        * be checked by kvm_vcpu_check_block() before blocking.  The

        * memory barrier implicit in set_current_state orders writing

        * IsRunning=0 before reading the vIRR.  The processor needs a

        * matching memory barrier on interrupt delivery between writing

        * IRR and reading IsRunning; the lack of this barrier might be

        * the cause of errata #1235).

	 * Note, any IRQs that arrive before IsRunning=0 will not cause an

	 * incomplete IPI vmexit on the source; kvm_vcpu_check_block() handles

	 * this by checking vIRR one last time before blocking.  The memory

	 * barrier implicit in set_current_state orders writing IsRunning=0

	 * before reading the vIRR.  The processor needs a matching memory

	 * barrier on interrupt delivery between writing IRR and reading

	 * IsRunning; the lack of this barrier might be the cause of errata #1235).

	 *

	 * Clear IsRunning=0 even if guest IRQs are disabled, i.e. even if KVM

	 * doesn't need to detect events for scheduling purposes.  The doorbell

	 * used to signal running vCPUs cannot be blocked, i.e. will perturb the

	 * CPU and cause noisy neighbor problems if the VM is sending interrupts

	 * to the vCPU while it's scheduled out.

	 */

	avic_vcpu_put(vcpu);

}