[edk2-devel] [PATCH 0/9] ArmVirtPkg: support two PL011 UARTs

[Gerd Hoffmann]

  Hi,

> So, for this purpose, only the following could have a chance of working:
> 
> - Expose a new config option on the QEMU command line to the user,
> regarding the intended use of the serial port(s). This could be of any
> tolerable form (machine property, front-end (device) property, whatever
> -- anything that QEMU reviewers can accept).
> 
> - In QEMU, generate both the DT and the ACPI tables accordingly. The
> ACPI tables would have to immediately *not* contain the UART-to-hide (so
> as to keep it secret from the guest OS). The DT at the same time would
> still have to expose the "runtime DEBUG UART", because edk2 would have
> to know where that UART was (and that it was meant specifically for OS
> runtime debug output).
> 
> - Edk2 would have to patch the DT (we tend to do that already), because
> (in some configs) we do forward the DT to the guest OS. This need for
> patching could be lifted if QEMU adopted such a form of expression for
> the "runtime DEBUG UART" that would be ignored by Linux out of the box.

That approach looks best to me.  It allows the user to specify on the
qemu command line what the ports should be used for, which is IMHO the
most convenient option.  qemu generates the complete DSDT anyway, so
it's trivial to add/remove serial ports there, and for the DT we have
libfdt to do the work needed.

take care,
  Gerd



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