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> + let tail = regs::NV_PFSP_MSGQ_TAIL::read(bar).address(); > + > + if head == tail { > + return 0; > + } > + > + // TAIL points at last DWORD written, so add 4 to get total size > + (tail - head) + 4 > + } > + Can we harden against integer underflow here? Even if tail is always >= head in normal operation, I think we should prepare for underflow due to misbehaving HW etc to avoid producing a massive integer, how about: tail.saturating_sub(head) + 4 Thanks.