KVM-PR no longer works when compiled with new GCC compilers

KVM-PR no longer works when compiled with new GCC compilers

[Christian Zigotzky]

Hello,

KVM-PR (-enable-kvm) doesn't work anymore on our PA Semi Nemo boards [1] 
if we compiled it with new GCC compilers.
The VM can't boot. There aren't any messages on the serial console of QEMU.

It boots without KVM-PR.

Kernel config with new GCC compiler [2]:

- CONFIG_CC_VERSION_TEXT="powerpc64-suse-linux-gcc (SUSE Linux) 11.5.0"
- CONFIG_TARGET_CPU="power4"
- CONFIG_TUNE_CPU="-mtune=power10"

It works if I compile it with an old GCC compiler [3]:

- CONFIG_CC_VERSION_TEXT="powerpc-linux-gnu-gcc (Ubuntu 
9.4.0-1ubuntu1~20.04.1) 9.4.0"
- CONFIG_TARGET_CPU="power4"
- CONFIG_TUNE_CPU="-mtune=power9"

Mtune changes to power9 automatically if I compiled it with an old GCC 
compiler. If I compile it with a new GCC compiler again it changes 
automatically to mtune=power10.

Is mtune the reason of the KVM-PR issue? I think the issue is the new 
GCC. [4]

Could you please check whether KVM-PR is compatible with new versions of 
GCC compilers?

Thanks in advance,

Christian



[1] https://en.wikipedia.org/wiki/AmigaOne_X1000

[2] 
https://github.com/chzigotzky/kernels/blob/45186997e6f347fd092f9ab629d62d6041426227/configs/x1000_defconfig

[3] 
https://github.com/chzigotzky/kernels/blob/bc7a3e27b3fcdee52a8135435f02cf807a43872a/configs/x1000_defconfig

[4] KVM-PR no longer works on an X1000 if the kernel has been compiled 
with a new GCC: 
https://forum.hyperion-entertainment.com/viewtopic.php?p=57146#p57146

Re: KVM-PR no longer works when compiled with new GCC compilers

[Christophe Leroy]

Le 02/10/2025 à 08:37, Christian Zigotzky a écrit :
> Hello,
> 
> KVM-PR (-enable-kvm) doesn't work anymore on our PA Semi Nemo boards [1] 
> if we compiled it with new GCC compilers.
> The VM can't boot. There aren't any messages on the serial console of QEMU.
> 
> It boots without KVM-PR.
> 
> Kernel config with new GCC compiler [2]:
> 
> - CONFIG_CC_VERSION_TEXT="powerpc64-suse-linux-gcc (SUSE Linux) 11.5.0"
> - CONFIG_TARGET_CPU="power4"
> - CONFIG_TUNE_CPU="-mtune=power10"
> 
> It works if I compile it with an old GCC compiler [3]:
> 
> - CONFIG_CC_VERSION_TEXT="powerpc-linux-gnu-gcc (Ubuntu 
> 9.4.0-1ubuntu1~20.04.1) 9.4.0"
> - CONFIG_TARGET_CPU="power4"
> - CONFIG_TUNE_CPU="-mtune=power9"
> 
> Mtune changes to power9 automatically if I compiled it with an old GCC 
> compiler. If I compile it with a new GCC compiler again it changes 
> automatically to mtune=power10.
> 
> Is mtune the reason of the KVM-PR issue? I think the issue is the new 
> GCC. [4]
> 
> Could you please check whether KVM-PR is compatible with new versions of 
> GCC compilers?

On your side, can you try with the following hack to test new GCC + 
CONFIG_TUNE_CPU="-mtune=power9"

diff --git a/arch/powerpc/platforms/Kconfig.cputype 
b/arch/powerpc/platforms/Kconfig.cputype
index 7b527d18aa5e..b8480cdb3a9a 100644
--- a/arch/powerpc/platforms/Kconfig.cputype
+++ b/arch/powerpc/platforms/Kconfig.cputype
@@ -264,7 +264,6 @@ config TARGET_CPU
  config TUNE_CPU
  	string
  	depends on POWERPC64_CPU
-	default "-mtune=power10" if $(cc-option,-mtune=power10)
  	default "-mtune=power9"  if $(cc-option,-mtune=power9)
  	default "-mtune=power8"  if $(cc-option,-mtune=power8)



> 
> Thanks in advance,
> 
> Christian
> 
> 
> 
> [1] https://eur01.safelinks.protection.outlook.com/? 
> url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FAmigaOne_X1000&data=05%7C02%7Cchristophe.leroy2%40cs-soprasteria.com%7C0ca7898bcfed40a2839108de017ea0b4%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C638949840566572384%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=9U0DLwRhoWagfDe4bTRCdHZpf52tvZbXAMGE8jHibyU%3D&reserved=0
> 
> [2] https://eur01.safelinks.protection.outlook.com/? 
> url=https%3A%2F%2Fgithub.com%2Fchzigotzky%2Fkernels%2Fblob%2F45186997e6f347fd092f9ab629d62d6041426227%2Fconfigs%2Fx1000_defconfig&data=05%7C02%7Cchristophe.leroy2%40cs-soprasteria.com%7C0ca7898bcfed40a2839108de017ea0b4%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C638949840566592849%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=KAcTs9%2BiNnjhKkvlW6JHsiRts0uRBp0Oza56rVZRxvs%3D&reserved=0
> 
> [3] https://eur01.safelinks.protection.outlook.com/? 
> url=https%3A%2F%2Fgithub.com%2Fchzigotzky%2Fkernels%2Fblob%2Fbc7a3e27b3fcdee52a8135435f02cf807a43872a%2Fconfigs%2Fx1000_defconfig&data=05%7C02%7Cchristophe.leroy2%40cs-soprasteria.com%7C0ca7898bcfed40a2839108de017ea0b4%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C638949840566604830%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=FTh46dqFpLZyNrnhVgjHgUrlG689ryfymogE9oAVhE4%3D&reserved=0
> 
> [4] KVM-PR no longer works on an X1000 if the kernel has been compiled 
> with a new GCC: https://eur01.safelinks.protection.outlook.com/? 
> url=https%3A%2F%2Fforum.hyperion- 
> entertainment.com%2Fviewtopic.php%3Fp%3D57146%23p57146&data=05%7C02%7Cchristophe.leroy2%40cs-soprasteria.com%7C0ca7898bcfed40a2839108de017ea0b4%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C638949840566617191%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=ih%2FgNl3HKEavfrn%2ByHM9J3ZpZvztC95aWUhC%2Fy1YjiQ%3D&reserved=0
>