[edk2-devel] EFI shell with microvm

[Boeuf, Sebastien]

On Fri, 2022-01-07 at 13:07 +0100, kraxel at redhat.com wrote:
>   Hi,
> 
> > > microvm has no lpc bridge, so I had to do it in a different way
> > > ...
> > 
> > Cloud Hypervisor doesn't emulate any LPC bridge or ISA bus.
> 
> Ok, doing it microvm-style makes sense then.

Ok thanks for the confirmation. Hopefully it won't conflict with what
QEMU uses/needs.

> 
> > > Works fine for me.
> > > 
> > > qemu-system-x86_64 -nographic -machine microvm,rtc=on -bios
> > > Build/MicrovmX64/DEBUG_GCC5/FV/MICROVM.fd
> > 
> > Thanks for the confirmation, something might be wrong with the
> > interrupt used for my serial device.
> 
> tianocore doesn't use interrupts (other than timer).

Yes I realized that by diving into the code. I can see microvm using
the Xen timer while OvmfPkgX64 uses 8254 PIT.

> 
> > Cloud Hypervisor only has an IOAPIC, it doesn't rely on any PIC,
> > which
> > is why I'm not sure what might be missing to get the EFI shell to
> > receive the interrupts.
> 
> PIC is optional for microvm too, and everything works fine for me
> with
> "-machine microvm,rtc=on,pic=off,pit=off"

Yes that's interesting and after some investigations I think the
problem is that I don't get TerminalConInTimerHandler handler to be
triggered. I can see the handler is correctly registered but for some
reasons, it's never used. I'm wondering if that might be an issue
related to a lack of timer support. Especially I see the UEFI service
SetTimer() is being used for the polling mechanism, so I wonder what is
the backend for it.

> 
> take care,
>   Gerd
> 

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