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
> 

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

[Christian Zigotzky]

On 02/10/25 08:37, Christian Zigotzky wrote:
> 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
>
Error messages (kvm-pr compiled with powerpc64-linux-gnu-gcc 14.1.1 
20240507 Red Hat Cross 14.1.1-1, GNU ld version 2.41-2.el10_0):

[  800.274759] Couldn't emulate instruction 0x00000000 (op 0 xop 0)
[  800.274767] kvmppc_exit_pr_progint: emulation at 100 failed (00000000)

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

[John Paul Adrian Glaubitz]

Hi Christian,

On Thu, 2026-04-23 at 18:50 +0200, Christian Zigotzky wrote:
> On 02/10/25 08:37, Christian Zigotzky wrote:
> > 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
> > 
> Error messages (kvm-pr compiled with powerpc64-linux-gnu-gcc 14.1.1 
> 20240507 Red Hat Cross 14.1.1-1, GNU ld version 2.41-2.el10_0):
> 
> [  800.274759] Couldn't emulate instruction 0x00000000 (op 0 xop 0)
> [  800.274767] kvmppc_exit_pr_progint: emulation at 100 failed (00000000)

I don't think "mtune=power9" or "mtune=power10" will work. Did you try "mtune=power4"?

Adrian

-- 
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer
`. `'   Physicist
  `-    GPG: 62FF 8A75 84E0 2956 9546  0006 7426 3B37 F5B5 F913

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

[Christian Zigotzky]

On 23 April 2026 at 07:35 pm, John Paul Adrian Glaubitz wrote:
> Hi Christian,
>
> On Thu, 2026-04-23 at 18:50 +0200, Christian Zigotzky wrote:
>> On 02/10/25 08:37, Christian Zigotzky wrote:
>>> 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
>>>
>> Error messages (kvm-pr compiled with powerpc64-linux-gnu-gcc 14.1.1
>> 20240507 Red Hat Cross 14.1.1-1, GNU ld version 2.41-2.el10_0):
>>
>> [  800.274759] Couldn't emulate instruction 0x00000000 (op 0 xop 0)
>> [  800.274767] kvmppc_exit_pr_progint: emulation at 100 failed (00000000)
> I don't think "mtune=power9" or "mtune=power10" will work. Did you try "mtune=power4"?
>
> Adrian
>
I haven't tried it yet, but I'm going to give it a try.

Christian

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

[Christian Zigotzky]

On 23/04/26 19:46, Christian Zigotzky wrote:
> On 23 April 2026 at 07:35 pm, John Paul Adrian Glaubitz wrote:
>> Hi Christian,
>>
>> On Thu, 2026-04-23 at 18:50 +0200, Christian Zigotzky wrote:
>>> On 02/10/25 08:37, Christian Zigotzky wrote:
>>>> 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
>>>>
>>> Error messages (kvm-pr compiled with powerpc64-linux-gnu-gcc 14.1.1
>>> 20240507 Red Hat Cross 14.1.1-1, GNU ld version 2.41-2.el10_0):
>>>
>>> [  800.274759] Couldn't emulate instruction 0x00000000 (op 0 xop 0)
>>> [  800.274767] kvmppc_exit_pr_progint: emulation at 100 failed 
>>> (00000000)
>> I don't think "mtune=power9" or "mtune=power10" will work. Did you 
>> try "mtune=power4"?
>>
>> Adrian
>>
> I haven't tried it yet, but I'm going to give it a try.
>
> Christian
I compiled it with "mtune=power4" today but without any success.

Error messages:

[  800.274759] Couldn't emulate instruction 0x00000000 (op 0 xop 0)
[  800.274767] kvmppc_exit_pr_progint: emulation at 100 failed (00000000)

Christian

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

[John Paul Adrian Glaubitz]

On Fri, 2026-04-24 at 16:47 +0200, Christian Zigotzky wrote:
> I compiled it with "mtune=power4" today but without any success.
> 
> Error messages:
> 
> [  800.274759] Couldn't emulate instruction 0x00000000 (op 0 xop 0)
> [  800.274767] kvmppc_exit_pr_progint: emulation at 100 failed (00000000)

What exactly are you running inside the KVM? 0x00000000 doesn't seem like
a valid instruction and a quick Google research reveals that this triggers
a SIGLL trap.

Adrian

-- 
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer
`. `'   Physicist
  `-    GPG: 62FF 8A75 84E0 2956 9546  0006 7426 3B37 F5B5 F913

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

[Segher Boessenkool]

On Fri, Apr 24, 2026 at 05:48:37PM +0200, John Paul Adrian Glaubitz wrote:
> On Fri, 2026-04-24 at 16:47 +0200, Christian Zigotzky wrote:
> > I compiled it with "mtune=power4" today but without any success.
> > 
> > Error messages:
> > 
> > [  800.274759] Couldn't emulate instruction 0x00000000 (op 0 xop 0)
> > [  800.274767] kvmppc_exit_pr_progint: emulation at 100 failed (00000000)
> 
> What exactly are you running inside the KVM? 0x00000000 doesn't seem like
> a valid instruction and a quick Google research reveals that this triggers
> a SIGLL trap.

By definition anything with primary op 0 (the first six bits 0) is
invalid.  It isn't super unusual to (accidentally) try to execute a zero
as an instruction ;-)


Segher