Why SPDM session must be established before GSP-RM boots

Accelerated Computing Confidential Computing
1

I find that during the bootstrap of gsp (in kernel_gsp_gh100.c), the SPDM session must be established before GSP-RM boots. Is there any step in the subsequent bootstrap process must rely on an SPDM session？

2

SPDM is used to establish a secure session with symmetric keys between the CPU and GPU. Every subsequent boot command from CPU to GPU is encrypted, so pretty much everything relies on SPDM. After boot has completed SPDM is also used to authenticate the GPU and assess its measurements by the Verifier.