Direct injection of SPIs

I am reading GIC-700 TRM, and seems that it can directly inject SGIs/LPIs into virtual machine without be trapped into Hypervisor. Unfortunately, SPIs direct injection is not supported. I am wondering if there is some special considerations to not suppport SPI direct injection? To me, if there is options to configure every single SPI to trap or not into Hypervisor, the performance will be better. 

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