From: Nicolin Chen nicolinc@nvidia.com Sent: Friday, May 9, 2025 11:03 AM
To simplify the mappings from global VCMDQs to VINTFs' LVCMDQs, the design chose to do static allocations and mappings in the global reset function.
However, with the user-owned VINTF support, it exposes a security concern: if user space VM only wants one LVCMDQ for a VINTF, statically mapping two or more LVCMDQs creates a hidden VCMDQ that user space could DoS attack by writing random stuff to overwhelm the kernel with unhandleable IRQs.
Thus, to support the user-owned VINTF feature, a LVCMDQ mapping has to be done dynamically.
HW allows pre-assigning global VCMDQs in the CMDQ_ALLOC registers, without finalizing the mappings by keeping CMDQV_CMDQ_ALLOCATED=0. So, add a pair of map/unmap helper that simply sets/clears that bit.
Delay the LVCMDQ mappings to tegra241_vintf_hw_init(), and the unmappings to tegra241_vintf_hw_deinit().
I don't know the specifics of tegra241-cmdqv. But the current description is a bit misleading. for native tegra241_vintf_hw_init() is called from reset so the mapping is still enabled in that path. for user-owned then tegra241_vcmdq_map_lvcmdq() is called from tegra241_vintf_alloc_lvcmdq_user() instead of tegra241_vintf_hw_init().
so nothing is actually delayed in this patch.