ppc/pnv: Add a big-core mode that joins two regular cores

POWER9 and POWER10 machines come in two variants, big-core and
small-core. Big-core machines are SMT8 from software's point of view,
but the low level platform topology ("xscom registers and pervasive
addressing"), these look more like a pair of small cores ganged
together.

Presently the way this is modelled is to create one SMT8 PnvCore and add
special cases to xscom and pervasive for big-core mode that tries to
split this into two small cores, but this is becoming too complicated to
manage.

A better approach is to create 2 core structures and ganging them
together to look like an SMT8 core in TCG. Then the xscom and pervasive
models mostly do not need to differentiate big and small core modes.

This change adds initial mode bits and QEMU topology handling to
split SMT8 cores into 2xSMT4 cores.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>

3 files changed, 4 insertions, 0 deletions

diff --git a/include/hw/ppc/pnv.h b/include/hw/ppc/pnv.h
index 1993dededf..283ddd50e7 100644
--- a/include/hw/ppc/pnv.h
+++ b/include/hw/ppc/pnv.h
@@ -101,6 +101,8 @@ struct PnvMachineState {
     PnvPnor      *pnor;
 
     hwaddr       fw_load_addr;
+
+    bool         big_core;
 };
 
 PnvChip *pnv_get_chip(PnvMachineState *pnv, uint32_t chip_id);
diff --git a/include/hw/ppc/pnv_chip.h b/include/hw/ppc/pnv_chip.h
index 7d5d08bcdc..69d8273efe 100644
--- a/include/hw/ppc/pnv_chip.h
+++ b/include/hw/ppc/pnv_chip.h
@@ -27,6 +27,7 @@ struct PnvChip {
     uint64_t     ram_start;
     uint64_t     ram_size;
 
+    bool         big_core;
     uint32_t     nr_cores;
     uint32_t     nr_threads;
     uint64_t     cores_mask;
diff --git a/include/hw/ppc/pnv_core.h b/include/hw/ppc/pnv_core.h
index 693acb189b..50164e9e1f 100644
--- a/include/hw/ppc/pnv_core.h
+++ b/include/hw/ppc/pnv_core.h
@@ -49,6 +49,7 @@ struct PnvCore {
 
     /*< public >*/
     PowerPCCPU **threads;
+    bool big_core;
     uint32_t pir;
     uint32_t hwid;
     uint64_t hrmor;