Constant VMO_VECTOR_MAX 

pub const VMO_VECTOR_MAX: u32 = 64; // 64u32

Limit on the number of VMOs in one call to RegisterVmos() or UnregisterVmos(). Bounded by the Zircon channel handle limit (ZX_CHANNEL_MAX_MSG_HANDLES = 64) since RegisterVmos() returns a vector of VMO handles.