GICv3&4 : What is the purpose of Direct Injection of Virtual Interrupts.?

Hi Everyone,

Its true that Hypervisor inserts interrupt in the virtual machine.

But, GICv4 also tells that it supports direct injection of virtual interrupts  which means that, interrupt can be inserted directly to VM from Redistributor without involvement of Hypervisor.

Indicated by Register : ICH_VTR_EL2

Field                           : nV4

If this field bit is:

     0 - Supports Direct Injection of Virtual Interrupts

     1 - Does not Support Direct Injection of Virtual Interrupts.

So, from above statement can you please help me in understanding about,

     - In what scenarios does this direct injection of Virtual Interrupts happen..?

     - Is that okay, if Hypervisor is not updated about the virtual interrupt and virtual interrupt is  directly inserted from Redistributor to VM.

     - Can you also please tell me what is the advantage of having this feature.

Above doubts arose as per my understanding on reading GICv4 Document. If i am missing any clarity please excuse & suggest me. I am happy to take anything.

Thanks in advance,

Rakesh.