We have discovered a case where Dispatch() will fail to dispatch pending SMM
drivers. It happens when a FV contains only pending SMM drivers, but no pending
DXE drivers and Dispatch() is called. The offending code is in CoreDispatcher()
CoreDispatcher ()
{
...
ReturnStatus = EFI_NOT_FOUND;
do { // Dispatcher_Loop
Dispatch DXE modules;
if any module is dispatched, ReturnStatus is set to EFI_SUCCESS;
...
//
// Now DXE Dispatcher finished one round of dispatch, signal an event group
// so that SMM Dispatcher get chance to dispatch SMM Drivers which depend
// on UEFI protocols
//
if (!EFI_ERROR (ReturnStatus)) {
CoreSignalEvent (DxeDispatchEvent); // trigger SMM dispatcher
}
...
}
...
}
}
The existing logic only dispatches SMM modules if a DXE module was dispatched.
This works well for most use cases, since there are always a mixture of DXE and
SMM drivers. But in specialized FVs (or in some other specialized cases), if
there are only SMM drivers, none will be launched. I believe the solution is to
force the SMM dispatcher to run at least once, perhaps by using a BOOLEAN that
is initially set to FALSE (SmmDriverDispatched) and then adding that as an ||
condition to the bolded line above.
Regards,
Tim
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