Power9 CPUs have a core thread state register accessible via SPRC/SPRD
indirect registers. This register includes a bit for big-core mode,
which skiboot requires.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 target/ppc/misc_helper.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/target/ppc/misc_helper.c b/target/ppc/misc_helper.c
index 692e48e6bc..e69236d2de 100644
--- a/target/ppc/misc_helper.c
+++ b/target/ppc/misc_helper.c
@@ -319,6 +319,23 @@ target_ulong helper_load_sprd(CPUPPCState *env)
     case 0: /* SCRATCH0-3 */
     case 1: /* SCRATCH4-7 */
         return pc->scratch[(sprc >> 3) & 0x7];
+
+    case 0x1e0: /* core thread state */
+        if (env->excp_model == POWERPC_EXCP_POWER9) {
+            /*
+             * Only implement for POWER9 because skiboot uses it to check
+             * big-core mode. Other bits are unimplemented so we would
+             * prefer to get unimplemented message on POWER10 if it were
+             * used anywhere.
+             */
+            if (pc->big_core) {
+                return PPC_BIT(63);
+            } else {
+                return 0;
+            }
+        }
+        /* fallthru */
+
     default:
         qemu_log_mask(LOG_UNIMP, "mfSPRD: Unimplemented SPRC:0x"
                                   TARGET_FMT_lx"\n", sprc);
-- 
2.45.1

On 7/16/24 18:26, Nicholas Piggin wrote:
> Power9 CPUs have a core thread state register accessible via SPRC/SPRD
> indirect registers. This register includes a bit for big-core mode,
> which skiboot requires.
> 
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>


Reviewed-by: Cédric Le Goater <clg@redhat.com>

Thanks,

C.


> ---
>   target/ppc/misc_helper.c | 17 +++++++++++++++++
>   1 file changed, 17 insertions(+)
> 
> diff --git a/target/ppc/misc_helper.c b/target/ppc/misc_helper.c
> index 692e48e6bc..e69236d2de 100644
> --- a/target/ppc/misc_helper.c
> +++ b/target/ppc/misc_helper.c
> @@ -319,6 +319,23 @@ target_ulong helper_load_sprd(CPUPPCState *env)
>       case 0: /* SCRATCH0-3 */
>       case 1: /* SCRATCH4-7 */
>           return pc->scratch[(sprc >> 3) & 0x7];
> +
> +    case 0x1e0: /* core thread state */
> +        if (env->excp_model == POWERPC_EXCP_POWER9) {
> +            /*
> +             * Only implement for POWER9 because skiboot uses it to check
> +             * big-core mode. Other bits are unimplemented so we would
> +             * prefer to get unimplemented message on POWER10 if it were
> +             * used anywhere.
> +             */
> +            if (pc->big_core) {
> +                return PPC_BIT(63);
> +            } else {
> +                return 0;
> +            }
> +        }
> +        /* fallthru */
> +
>       default:
>           qemu_log_mask(LOG_UNIMP, "mfSPRD: Unimplemented SPRC:0x"
>                                     TARGET_FMT_lx"\n", sprc);