Re: [PULL 1/2] target/ppc: Big-core scratch register fix

[Thomas Huth]

On 08/04/2025 14.45, Nicholas Piggin wrote:
The per-core SCRATCH0-7 registers are shared between big cores, which
was missed in the big-core implementation. It is difficult to model
well with the big-core == 2xPnvCore scheme we moved to, this fix
uses the even PnvCore to store the scrach data.
Also remove a stray log message that came in with the same patch that
introduced patch.

Fixes: c26504afd5f5c ("ppc/pnv: Add a big-core mode that joins two regular 
cores")
Cc: qemu-sta...@nongnu.org
Signed-off-by: Nicholas Piggin <npig...@gmail.com>
---
  target/ppc/misc_helper.c | 9 ++++++++-
  1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/target/ppc/misc_helper.c b/target/ppc/misc_helper.c
index 2d9512c116..46ae454afd 100644
--- a/target/ppc/misc_helper.c
+++ b/target/ppc/misc_helper.c
@@ -332,6 +332,10 @@ target_ulong helper_load_sprd(CPUPPCState *env)
      PnvCore *pc = pnv_cpu_state(cpu)->pnv_core;
      target_ulong sprc = env->spr[SPR_POWER_SPRC];
  
+    if (pc->big_core) {
+        pc = pnv_chip_find_core(pc->chip, CPU_CORE(pc)->core_id & ~0x1);
+    }
+
      switch (sprc & 0x3e0) {
      case 0: /* SCRATCH0-3 */
      case 1: /* SCRATCH4-7 */
@@ -368,6 +372,10 @@ void helper_store_sprd(CPUPPCState *env, target_ulong val)
      PnvCore *pc = pnv_cpu_state(cpu)->pnv_core;
      int nr;
  
+    if (pc->big_core) {
+        pc = pnv_chip_find_core(pc->chip, CPU_CORE(pc)->core_id & ~0x1);
+    }
+

 Hi Nicholas,

this patch breaks compilation when QEMU has been configured with 
"--without-default-devices" :

FAILED: qemu-system-ppc64
cc -m64 @qemu-system-ppc64.rsp
/usr/bin/ld: libqemu-ppc64-softmmu.a.p/target_ppc_misc_helper.c.o: in 
function `helper_load_sprd':
.../qemu/target/ppc/misc_helper.c:336:(.text+0xcab): undefined reference to 
`pnv_chip_find_core'
/usr/bin/ld: libqemu-ppc64-softmmu.a.p/target_ppc_misc_helper.c.o: in 
function `helper_store_sprd':
.../qemu/target/ppc/misc_helper.c:376:(.text+0xda3): undefined reference to 
`pnv_chip_find_core'
collect2: error: ld returned 1 exit status

Could you please have a look?

 Thanks,
  Thomas