USER_CTX_SIZE
#define WPTR_OFFSET(addr) ((addr) + USER_CTX_SIZE - sizeof(u64))
#define RPTR_OFFSET(addr) ((addr) + USER_CTX_SIZE - sizeof(u64) * 2)
#define FENCE_OFFSET(addr) ((addr) + USER_CTX_SIZE - sizeof(u64) * 3)
&ctx_ptr, USER_CTX_SIZE);
USER_CTX_VA, USER_CTX_SIZE);
memset(ctx_ptr, 0, USER_CTX_SIZE);