Re: [PATCH for-7.2 00/10] add hmp 'save-fdt' and 'info fdt' commands

[BALATON Zoltan]

On Fri, 22 Jul 2022, Daniel Henrique Barboza wrote:
> Hi,
>
> After dealing with a FDT element that isn't being shown in the userspace
> and having to shutdown the guest, dump the FDT using 'machine -dumpdtb' and
> then using 'dtc' to see what was inside the FDT, I thought it was a good
> idea to add extra support for FDT handling in QEMU.
>
> This series introduces 2 commands. 'fdt-save' behaves similar to what
> 'machine -dumpdtb' does, with the advantage of saving the FDT of a running
> guest on demand. This command is implemented in patch 03.
>
> The second command, 'info fdt <command>' is more sophisticated. This
> command can print specific nodes and properties of the FDT. A few
> examples:
>
> - print the /cpus/cpu@0 from an ARM 'virt' machine:
>
> (qemu) info fdt /cpus/cpu@0
> /cpus/cpu@0 {
>    phandle = <0x8001>
>    reg = <0x0>
>    compatible = 'arm,cortex-a57'
>    device_type = 'cpu'
> }
> (qemu)
>
> - print the device_type property of the interrupt-controller node of a
> pSeries machine:
>
> (qemu) info fdt /interrupt-controller/device_type
> /interrupt-controller/device_type = 'PowerPC-External-Interrupt-Presentation'
> (qemu)
>
> Issuing a 'info fdt /' will dump all the FDT. 'info fdt' is implemented
> in patches 4-10.
>
> Both 'fdt-save' and 'info fdt' works across machines and archs based on
> two premises: the FDT must be created using libfdt (which is the case of
> all FDTs created with device_tree.c helpers and the _FDT macro) and the
> FDT must be reachable via MachineState->fdt.
>
> To meet the prerequisites for ARM machines, patch 1 makes a change in
> arm_load_dtb(). Patches 2 and 3 makes a similar change for two PowerPC
> machines that weren't using machine->fdt.

There are some other machines that load a dtb with load_device_tree(). Do 
they need some patches too?

Regards,
BALATON Zoltan

> Tests were done using the ARM machvirt machine and ppc64 pSeries
> machine, but any machine that meets the forementioned conditions will be
> supported by these 2 new commands.
>
>
> Daniel Henrique Barboza (10):
>  hw/arm/boot.c: do not free machine->fdt in arm_load_dtb()
>  hw/ppc/pegasos2.c: set machine->fdt in machine_reset()
>  hw/ppc: set machine->fdt in spapr machine
>  hmp, device_tree.c: introduce fdt-save
>  hmp, device_tree.c: introduce 'info fdt' command
>  device_tree.c: support printing of strings props
>  device_tree.c: support remaining FDT prop types
>  device_node.c: enable 'info fdt' to print subnodes
>  device_tree.c: add fdt_print_property() helper
>  hmp, device_tree.c: add 'info fdt <property>' support
>
> hmp-commands-info.hx         |  13 +++
> hmp-commands.hx              |  13 +++
> hw/arm/boot.c                |   3 +-
> hw/ppc/pegasos2.c            |   3 +
> hw/ppc/spapr.c               |   3 +
> hw/ppc/spapr_hcall.c         |   3 +
> include/sysemu/device_tree.h |   3 +
> monitor/misc.c               |  25 ++++
> softmmu/device_tree.c        | 219 +++++++++++++++++++++++++++++++++++
> 9 files changed, 284 insertions(+), 1 deletion(-)