Shiyang Ruan wrote: [..] > >> My expectation is MF_ACTION_REQUIRED is not appropriate for CXL event > >> reported errors since action is only required for direct consumption > >> events and those need not be reported through the device event queue. > > Got it. > > I'm not very sure about 'Host write/read' type. In my opinion, these > two types of event should be sent from device when CPU is accessing a > bad memory address, they could be thought of a sync event which needs
Hmm, no that's not my understanding of a sync event. I expect when error notifications are synchronous the CPU is guaranteed not to make forward progress past the point of encountering the error. MSI-signaled component-events are always asynchronous by that definition because the CPU is free running while the interrupt is in-flight. > the 'MF_ACTION_REQUIRED' flag. Then, we can determine the flag by the > types like this: > - CXL_EVENT_TRANSACTION_READ | CXL_EVENT_TRANSACTION_WRITE > => MF_ACTION_REQUIRED > - CXL_EVENT_TRANSACTION_INJECT_POISON => MF_SW_SIMULATED > - others => 0 I doubt any reasonable policy can be inferred from the transaction type. Consider that the CPU itself does not take a sychronous exception when writes encounter poison. At most those are flagged via CMCI (corrected machine check interrupt). The only events that cause exceptions are CPU reads that consume poison. The device has no idea whether read events are coming from a CPU or a DMA event. MF_SW_SIMULATED is purely for software simulated poison events as injected poison can stil cause system fatal damage if the poison is ingested in an unrecoverable path. So, I think all CXL poison notification events should trigger an action optional memory_failure(). I expect this needs to make sure that duplicates re not a problem. I.e. in the case of CPU consumption of CXL poison, that causes a synchronous MF_ACTION_REQUIRED event via the MCE path *and* it may trigger the device to send an error record for the same page. As far as I can see, duplicate reports (MCE + CXL device) are unavoidable.
