[v7,10/14] hw/ppc: set machine->fdt in spapr machine

Commit Message

Daniel Henrique Barboza Sept. 8, 2022, 7:40 p.m. UTC

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 <[e-mail]>
Signed-off-by: Daniel Henrique Barboza <[e-mail]>
---
 hw/ppc/spapr.c       | 3 +++
 hw/ppc/spapr_hcall.c | 8 ++++++++
 2 files changed, 11 insertions(+)

Comments

Philippe Mathieu-Daudé Sept. 22, 2022, 10:56 a.m. UTC | #1

On 8/9/22 21:40, Daniel Henrique Barboza wrote:
> 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 <[e-mail]>
> Signed-off-by: Daniel Henrique Barboza <[e-mail]>
> ---
>   hw/ppc/spapr.c       | 3 +++
>   hw/ppc/spapr_hcall.c | 8 ++++++++
>   2 files changed, 11 insertions(+)

Reviewed-by: Philippe Mathieu-Daudé <[e-mail]>

Patch

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index fb790b61e4..170bbfd199 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;
 }