[PATCH v2 3/4] ppc/pnv: SMT support for powernv

[Nicholas Piggin]

Set the TIR default value with the SMT thread index, and place some
standard limits on SMT configurations. Now powernv is able to boot
skiboot and Linux with a SMT topology, including booting a KVM guest.

There are several SPRs and other features (e.g., broadcast msgsnd)
that are not implemented, but not used by OPAL or Linux and can be
added incrementally.

Reviewed-by: Cédric Le Goater <clg@kaod.org>
Tested-by: Cédric Le Goater <clg@kaod.org>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 docs/system/ppc/powernv.rst |  5 -----
 hw/ppc/pnv.c                | 12 ++++++++++++
 hw/ppc/pnv_core.c           | 13 +++++--------
 3 files changed, 17 insertions(+), 13 deletions(-)

diff --git a/docs/system/ppc/powernv.rst b/docs/system/ppc/powernv.rst
index c8f9762342..09f3965858 100644
--- a/docs/system/ppc/powernv.rst
+++ b/docs/system/ppc/powernv.rst
@@ -195,11 +195,6 @@ Use a MTD drive to add a PNOR to the machine, and get a 
NVRAM :
 
   -drive file=./witherspoon.pnor,format=raw,if=mtd
 
-CAVEATS
--------
-
- * No support for multiple HW threads (SMT=1). Same as pseries.
-
 Maintainer contact information
 ------------------------------
 
diff --git a/hw/ppc/pnv.c b/hw/ppc/pnv.c
index 5f25fe985a..23740f9d07 100644
--- a/hw/ppc/pnv.c
+++ b/hw/ppc/pnv.c
@@ -887,6 +887,18 @@ static void pnv_init(MachineState *machine)
 
     pnv->num_chips =
         machine->smp.max_cpus / (machine->smp.cores * machine->smp.threads);
+
+    if (machine->smp.threads > 8) {
+        error_report("Cannot support more than 8 threads/core "
+                     "on a powernv machine");
+        exit(1);
+    }
+    if (!is_power_of_2(machine->smp.threads)) {
+        error_report("Cannot support %d threads/core on a powernv"
+                     "machine because it must be a power of 2",
+                     machine->smp.threads);
+        exit(1);
+    }
     /*
      * TODO: should we decide on how many chips we can create based
      * on #cores and Venice vs. Murano vs. Naples chip type etc...,
diff --git a/hw/ppc/pnv_core.c b/hw/ppc/pnv_core.c
index ffbc29cbf4..17c267fa61 100644
--- a/hw/ppc/pnv_core.c
+++ b/hw/ppc/pnv_core.c
@@ -218,12 +218,13 @@ static const MemoryRegionOps pnv_core_power10_xscom_ops = 
{
     .endianness = DEVICE_BIG_ENDIAN,
 };
 
-static void pnv_core_cpu_realize(PnvCore *pc, PowerPCCPU *cpu, Error **errp)
+static void pnv_core_cpu_realize(PnvCore *pc, PowerPCCPU *cpu, Error **errp,
+                                 int thread_index)
 {
     CPUPPCState *env = &cpu->env;
     int core_pir;
-    int thread_index = 0; /* TODO: TCG supports only one thread */
     ppc_spr_t *pir = &env->spr_cb[SPR_PIR];
+    ppc_spr_t *tir = &env->spr_cb[SPR_TIR];
     Error *local_err = NULL;
     PnvChipClass *pcc = PNV_CHIP_GET_CLASS(pc->chip);
 
@@ -239,11 +240,7 @@ static void pnv_core_cpu_realize(PnvCore *pc, PowerPCCPU 
*cpu, Error **errp)
 
     core_pir = object_property_get_uint(OBJECT(pc), "pir", &error_abort);
 
-    /*
-     * The PIR of a thread is the core PIR + the thread index. We will
-     * need to find a way to get the thread index when TCG supports
-     * more than 1. We could use the object name ?
-     */
+    tir->default_value = thread_index;
     pir->default_value = core_pir + thread_index;
 
     /* Set time-base frequency to 512 MHz */
@@ -292,7 +289,7 @@ static void pnv_core_realize(DeviceState *dev, Error **errp)
     }
 
     for (j = 0; j < cc->nr_threads; j++) {
-        pnv_core_cpu_realize(pc, pc->threads[j], &local_err);
+        pnv_core_cpu_realize(pc, pc->threads[j], &local_err, j);
         if (local_err) {
             goto err;
         }
-- 
2.40.1