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

["Nicholas Piggin" <npiggin@gmail.com>]

On Thu Apr 24, 2025 at 6:25 PM AEST, Thomas Huth wrote:
> 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-stable@nongnu.org
>> Signed-off-by: Nicholas Piggin <npiggin@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 for the report, I have a hopefully simple fix just going through
CI now... Do you know if there's any reason to exclude a bunch of
targets in the build-without-defaults CI test? I wonder if we could just
enable all, it shouldn't add too much time to build test.

Thanks,
Nick