hw/ppc: set machine->fdt in spapr machine

The pSeries machine never bothered with the common machine->fdt
attribute. We do all the FDT related work using spapr->fdt_blob.

We're going to introduce a QMP/HMP command to dump the FDT, which will
rely on setting machine->fdt properly to work across all machine
archs/types.

Let's set machine->fdt in two places where we manipulate the FDT:
spapr_machine_reset() and CAS. There are other places where the FDT is
manipulated in the pSeries machines, most notably the hotplug/unplug
path. For now we'll acknowledge that we won't have the most accurate
representation of the FDT, depending on the current machine state, when
using this QMP/HMP fdt command. Making the internal FDT representation
always match the actual FDT representation that the guest is using is a
problem for another day.

spapr->fdt_blob is left untouched for now. To replace it with
machine->fdt, since we're migrating spapr->fdt_blob, we would need to
migrate machine->fdt as well. This is something that we would like to to
do keep our code simpler but it's also a work we'll leave for later.

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Message-Id: <20220926173855.1159396-14-danielhb413@gmail.com>

2 files changed, 11 insertions, 0 deletions

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index 8bbaf4f8a4..f79ac85ca1 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -1713,6 +1713,9 @@ static void spapr_machine_reset(MachineState *machine)
     spapr->fdt_initial_size = spapr->fdt_size;
     spapr->fdt_blob = fdt;
 
+    /* Set machine->fdt for 'dumpdtb' QMP/HMP command */
+    machine->fdt = fdt;
+
     /* Set up the entry state */
     first_ppc_cpu->env.gpr[5] = 0;
 
diff --git a/hw/ppc/spapr_hcall.c b/hw/ppc/spapr_hcall.c
index a8d4a6bcf0..891206e893 100644
--- a/hw/ppc/spapr_hcall.c
+++ b/hw/ppc/spapr_hcall.c
@@ -1256,6 +1256,14 @@ target_ulong do_client_architecture_support(PowerPCCPU *cpu,
     spapr->fdt_initial_size = spapr->fdt_size;
     spapr->fdt_blob = fdt;
 
+    /*
+     * Set the machine->fdt pointer again since we just freed
+     * it above (by freeing spapr->fdt_blob). We set this
+     * pointer to enable support for the 'dumpdtb' QMP/HMP
+     * command.
+     */
+    MACHINE(spapr)->fdt = fdt;
+
     return H_SUCCESS;
 }