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

[Daniel Henrique Barboza]

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.

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(-)

-- 
2.36.1