[linux-next:master 3139/4234] error: <unknown>:0:0: ran out of registers during register allocation in function 'hv_call_get_vp_registers'

[linux-next:master 3139/4234] error: <unknown>:0:0: ran out of registers during register allocation in function 'hv_call_get_vp_registers'

[kernel test robot]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
head:   0f4c93f7eb861acab537dbe94441817a270537bf
commit: 96a1d2495c2f48467a91b8657bd594350b84ea9e [3139/4234] Drivers: hv: Introduce mshv_vtl driver
config: i386-buildonly-randconfig-2003-20250824 (https://download.01.org/0day-ci/archive/20250824/202508240828.pVaUV45D-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250824/202508240828.pVaUV45D-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202508240828.pVaUV45D-lkp@intel.com/

All errors (new ones prefixed by >>):

>> error: <unknown>:0:0: ran out of registers during register allocation in function 'hv_call_get_vp_registers'
>> error: <unknown>:0:0: ran out of registers during register allocation in function 'hv_call_set_vp_registers'
>> error: <unknown>:0:0: ran out of registers during register allocation in function 'hv_call_get_partition_property'
   3 errors generated.

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [linux-next:master 3139/4234] error: <unknown>:0:0: ran out of registers during register allocation in function 'hv_call_get_vp_registers'

[Naman Jain]

On 8/24/2025 12:02 PM, kernel test robot wrote:
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
> head:   0f4c93f7eb861acab537dbe94441817a270537bf
> commit: 96a1d2495c2f48467a91b8657bd594350b84ea9e [3139/4234] Drivers: hv: Introduce mshv_vtl driver
> config: i386-buildonly-randconfig-2003-20250824 (https://download.01.org/0day-ci/archive/20250824/202508240828.pVaUV45D-lkp@intel.com/config)
> compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250824/202508240828.pVaUV45D-lkp@intel.com/reproduce)
> 
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@intel.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202508240828.pVaUV45D-lkp@intel.com/
> 
> All errors (new ones prefixed by >>):
> 
>>> error: <unknown>:0:0: ran out of registers during register allocation in function 'hv_call_get_vp_registers'
>>> error: <unknown>:0:0: ran out of registers during register allocation in function 'hv_call_set_vp_registers'
>>> error: <unknown>:0:0: ran out of registers during register allocation in function 'hv_call_get_partition_property'
>     3 errors generated.
> 

+Nathan

I can see a bunch of similar warnings previously reported, in different
functions, but could not find a fix for it, or if this
is a blocking error:

https://lore.kernel.org/all/?q=s%3A%22ran+out+of+registers+during+register+allocation%22

These all are reported on below 32 bit config, compiled with LLVM:
i386-buildonly-randconfig-*

Found previous comment from Nathan Chancellor, here, which seems to be
related to this error:
https://lore.kernel.org/all/20250507022649.GA1984217@ax162/

"""
This configuration has CONFIG_MATOM=y, which does not really work well
with clang for this reason and some others that have come up in the
past. Given it is likely that nobody will care enough to fix this on the
LLVM side (since it is 32-bit), we should probably just block using
MATOM with CC_IS_CLANG, which Arnd and I had talked about at the last
ClangBuiltLinux meeting.
"""

This gives me an impression that we can safely ignore these errors from 
kernel test bot.
Requesting Nathan to please correct me if I am wrong.

Regards,
Naman

Re: [linux-next:master 3139/4234] error: <unknown>:0:0: ran out of registers during register allocation in function 'hv_call_get_vp_registers'

[Nathan Chancellor]

Hi Naman,

On Sun, Aug 24, 2025 at 11:13:51PM +0530, Naman Jain wrote:
> 
> 
> On 8/24/2025 12:02 PM, kernel test robot wrote:
> > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
> > head:   0f4c93f7eb861acab537dbe94441817a270537bf
> > commit: 96a1d2495c2f48467a91b8657bd594350b84ea9e [3139/4234] Drivers: hv: Introduce mshv_vtl driver
> > config: i386-buildonly-randconfig-2003-20250824 (https://download.01.org/0day-ci/archive/20250824/202508240828.pVaUV45D-lkp@intel.com/config)
> > compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
> > reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250824/202508240828.pVaUV45D-lkp@intel.com/reproduce)
> > 
> > If you fix the issue in a separate patch/commit (i.e. not just a new version of
> > the same patch/commit), kindly add following tags
> > | Reported-by: kernel test robot <lkp@intel.com>
> > | Closes: https://lore.kernel.org/oe-kbuild-all/202508240828.pVaUV45D-lkp@intel.com/
> > 
> > All errors (new ones prefixed by >>):
> > 
> > > > error: <unknown>:0:0: ran out of registers during register allocation in function 'hv_call_get_vp_registers'
> > > > error: <unknown>:0:0: ran out of registers during register allocation in function 'hv_call_set_vp_registers'
> > > > error: <unknown>:0:0: ran out of registers during register allocation in function 'hv_call_get_partition_property'
> >     3 errors generated.
> > 
> 
> +Nathan
> 
> I can see a bunch of similar warnings previously reported, in different
> functions, but could not find a fix for it, or if this
> is a blocking error:
> 
> https://lore.kernel.org/all/?q=s%3A%22ran+out+of+registers+during+register+allocation%22
> 
> These all are reported on below 32 bit config, compiled with LLVM:
> i386-buildonly-randconfig-*
> 
> Found previous comment from Nathan Chancellor, here, which seems to be
> related to this error:
> https://lore.kernel.org/all/20250507022649.GA1984217@ax162/
> 
> """
> This configuration has CONFIG_MATOM=y, which does not really work well
> with clang for this reason and some others that have come up in the
> past. Given it is likely that nobody will care enough to fix this on the
> LLVM side (since it is 32-bit), we should probably just block using
> MATOM with CC_IS_CLANG, which Arnd and I had talked about at the last
> ClangBuiltLinux meeting.
> """
> 
> This gives me an impression that we can safely ignore these errors from
> kernel test bot.
> Requesting Nathan to please correct me if I am wrong.

Yes, this is all correct. I will try to pursue an actual kernel side fix
for this in Kconfig but I think the Intel folks can also start ignoring
these reports for ARCH=i386 and CONFIG_MATOM so that they do not get
sent to other kernel developers for random changes.

Cheers,
Nathan

RE: [linux-next:master 3139/4234] error: <unknown>:0:0: ran out of registers during register allocation in function 'hv_call_get_vp_registers'

[Michael Kelley]

From: Naman Jain <namjain@linux.microsoft.com> Sent: Sunday, August 24, 2025 10:44 AM
> 
> On 8/24/2025 12:02 PM, kernel test robot wrote:
> > tree: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
> > head:   0f4c93f7eb861acab537dbe94441817a270537bf
> > commit: 96a1d2495c2f48467a91b8657bd594350b84ea9e [3139/4234] Drivers: hv: Introduce mshv_vtl driver
> > config: i386-buildonly-randconfig-2003-20250824 (https://download.01.org/0day-ci/archive/20250824/202508240828.pVaUV45D-lkp@intel.com/config)
> > compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
> > reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250824/202508240828.pVaUV45D-lkp@intel.com/reproduce)
> >
> > If you fix the issue in a separate patch/commit (i.e. not just a new version of
> > the same patch/commit), kindly add following tags
> > | Reported-by: kernel test robot <lkp@intel.com>
> > | Closes: https://lore.kernel.org/oe-kbuild-all/202508240828.pVaUV45D-lkp@intel.com/
> >
> > All errors (new ones prefixed by >>):
> >
> >>> error: <unknown>:0:0: ran out of registers during register allocation in function 'hv_call_get_vp_registers'
> >>> error: <unknown>:0:0: ran out of registers during register allocation in function 'hv_call_set_vp_registers'
> >>> error: <unknown>:0:0: ran out of registers during register allocation in function 'hv_call_get_partition_property'
> >     3 errors generated.
> >

The other thing that's curious here is that these three functions are in
drivers/hv/mshv_common.c, which is only built on x64 and when
CONFIG_MSHV_ROOT or CONFIG_MSHV_VTL is set. None of these conditions 
are true for the supplied config file, so why is mshv_common.c being compiled?

Michael

> 
> +Nathan
> 
> I can see a bunch of similar warnings previously reported, in different
> functions, but could not find a fix for it, or if this
> is a blocking error:
> 
> https://lore.kernel.org/all/?q=s%3A%22ran+out+of+registers+during+register+allocation%22
> 
> These all are reported on below 32 bit config, compiled with LLVM:
> i386-buildonly-randconfig-*
> 
> Found previous comment from Nathan Chancellor, here, which seems to be
> related to this error: https://lore.kernel.org/all/20250507022649.GA1984217@ax162/
> 
> """
> This configuration has CONFIG_MATOM=y, which does not really work well
> with clang for this reason and some others that have come up in the
> past. Given it is likely that nobody will care enough to fix this on the
> LLVM side (since it is 32-bit), we should probably just block using
> MATOM with CC_IS_CLANG, which Arnd and I had talked about at the last
> ClangBuiltLinux meeting.
> """
> 
> This gives me an impression that we can safely ignore these errors from
> kernel test bot.
> Requesting Nathan to please correct me if I am wrong.
> 
> Regards,
> Naman

Re: [linux-next:master 3139/4234] error: <unknown>:0:0: ran out of registers during register allocation in function 'hv_call_get_vp_registers'

[Nathan Chancellor]

On Mon, Aug 25, 2025 at 05:06:53PM +0000, Michael Kelley wrote:
> From: Naman Jain <namjain@linux.microsoft.com> Sent: Sunday, August 24, 2025 10:44 AM
> > 
> > On 8/24/2025 12:02 PM, kernel test robot wrote:
> > > tree: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
> > > head:   0f4c93f7eb861acab537dbe94441817a270537bf
> > > commit: 96a1d2495c2f48467a91b8657bd594350b84ea9e [3139/4234] Drivers: hv: Introduce mshv_vtl driver
> > > config: i386-buildonly-randconfig-2003-20250824 (https://download.01.org/0day-ci/archive/20250824/202508240828.pVaUV45D-lkp@intel.com/config)
> > > compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
> > > reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250824/202508240828.pVaUV45D-lkp@intel.com/reproduce)
> > >
> > > If you fix the issue in a separate patch/commit (i.e. not just a new version of
> > > the same patch/commit), kindly add following tags
> > > | Reported-by: kernel test robot <lkp@intel.com>
> > > | Closes: https://lore.kernel.org/oe-kbuild-all/202508240828.pVaUV45D-lkp@intel.com/
> > >
> > > All errors (new ones prefixed by >>):
> > >
> > >>> error: <unknown>:0:0: ran out of registers during register allocation in function 'hv_call_get_vp_registers'
> > >>> error: <unknown>:0:0: ran out of registers during register allocation in function 'hv_call_set_vp_registers'
> > >>> error: <unknown>:0:0: ran out of registers during register allocation in function 'hv_call_get_partition_property'
> > >     3 errors generated.
> > >
> 
> The other thing that's curious here is that these three functions are in
> drivers/hv/mshv_common.c, which is only built on x64 and when
> CONFIG_MSHV_ROOT or CONFIG_MSHV_VTL is set. None of these conditions 
> are true for the supplied config file, so why is mshv_common.c being compiled?

Yeah, that is odd... FWIW, these are not the only functions that display this
error. On mainline with the same configuration.

  error: <unknown>:0:0: ran out of registers during register allocation in function 'hyperv_flush_guest_mapping'
  error: <unknown>:0:0: ran out of registers during register allocation in function 'hyperv_flush_guest_mapping_range'
  2 errors generated.
  make[6]: *** [scripts/Makefile.build:287: arch/x86/hyperv/nested.o] Error 1
  error: <unknown>:0:0: ran out of registers during register allocation in function 'hyperv_flush_tlb_multi'
  1 error generated.
  make[6]: *** [scripts/Makefile.build:287: arch/x86/hyperv/mmu.o] Error 1
  error: <unknown>:0:0: ran out of registers during register allocation in function 'hv_apicid_to_vp_index'
  1 error generated.
  make[6]: *** [scripts/Makefile.build:287: arch/x86/hyperv/hv_init.o] Error 1
  error: <unknown>:0:0: ran out of registers during register allocation in function 'hv_map_interrupt'
  error: <unknown>:0:0: ran out of registers during register allocation in function 'hv_unmap_interrupt'
  2 errors generated.
  make[6]: *** [scripts/Makefile.build:287: arch/x86/hyperv/irqdomain.o] Error 1
  make[6]: Target 'arch/x86/hyperv/' not remade because of errors.
  make[5]: *** [scripts/Makefile.build:556: arch/x86/hyperv] Error 2
  make[5]: Target 'arch/x86/' not remade because of errors.
  make[4]: *** [scripts/Makefile.build:556: arch/x86] Error 2
  error: <unknown>:0:0: ran out of registers during register allocation in function 'hv_post_message'
  1 error generated.
  make[6]: *** [scripts/Makefile.build:287: drivers/hv/hv.o] Error 1
  error: <unknown>:0:0: ran out of registers during register allocation in function 'hv_get_partition_id'
  error: <unknown>:0:0: ran out of registers during register allocation in function 'hv_query_ext_cap'
  2 errors generated.
  make[6]: *** [scripts/Makefile.build:287: drivers/hv/hv_common.o] Error 1

Cheers,
Nathan

Re: [linux-next:master 3139/4234] error: <unknown>:0:0: ran out of registers during register allocation in function 'hv_call_get_vp_registers'

[Naman Jain]

On 8/25/2025 10:30 PM, Nathan Chancellor wrote:
> Hi Naman,
> 
> On Sun, Aug 24, 2025 at 11:13:51PM +0530, Naman Jain wrote:
>>
>>
>> On 8/24/2025 12:02 PM, kernel test robot wrote:
>>> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
>>> head:   0f4c93f7eb861acab537dbe94441817a270537bf
>>> commit: 96a1d2495c2f48467a91b8657bd594350b84ea9e [3139/4234] Drivers: hv: Introduce mshv_vtl driver
>>> config: i386-buildonly-randconfig-2003-20250824 (https://download.01.org/0day-ci/archive/20250824/202508240828.pVaUV45D-lkp@intel.com/config)
>>> compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
>>> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250824/202508240828.pVaUV45D-lkp@intel.com/reproduce)
>>>
>>> If you fix the issue in a separate patch/commit (i.e. not just a new version of
>>> the same patch/commit), kindly add following tags
>>> | Reported-by: kernel test robot <lkp@intel.com>
>>> | Closes: https://lore.kernel.org/oe-kbuild-all/202508240828.pVaUV45D-lkp@intel.com/
>>>
>>> All errors (new ones prefixed by >>):
>>>
>>>>> error: <unknown>:0:0: ran out of registers during register allocation in function 'hv_call_get_vp_registers'
>>>>> error: <unknown>:0:0: ran out of registers during register allocation in function 'hv_call_set_vp_registers'
>>>>> error: <unknown>:0:0: ran out of registers during register allocation in function 'hv_call_get_partition_property'
>>>      3 errors generated.
>>>
>>
>> +Nathan
>>
>> I can see a bunch of similar warnings previously reported, in different
>> functions, but could not find a fix for it, or if this
>> is a blocking error:
>>
>> https://lore.kernel.org/all/?q=s%3A%22ran+out+of+registers+during+register+allocation%22
>>
>> These all are reported on below 32 bit config, compiled with LLVM:
>> i386-buildonly-randconfig-*
>>
>> Found previous comment from Nathan Chancellor, here, which seems to be
>> related to this error:
>> https://lore.kernel.org/all/20250507022649.GA1984217@ax162/
>>
>> """
>> This configuration has CONFIG_MATOM=y, which does not really work well
>> with clang for this reason and some others that have come up in the
>> past. Given it is likely that nobody will care enough to fix this on the
>> LLVM side (since it is 32-bit), we should probably just block using
>> MATOM with CC_IS_CLANG, which Arnd and I had talked about at the last
>> ClangBuiltLinux meeting.
>> """
>>
>> This gives me an impression that we can safely ignore these errors from
>> kernel test bot.
>> Requesting Nathan to please correct me if I am wrong.
> 
> Yes, this is all correct. I will try to pursue an actual kernel side fix
> for this in Kconfig but I think the Intel folks can also start ignoring
> these reports for ARCH=i386 and CONFIG_MATOM so that they do not get
> sent to other kernel developers for random changes.
> 
> Cheers,
> Nathan

Hi Nathan,
Thanks for confirming.

Regards,
Naman

Re: [linux-next:master 3139/4234] error: <unknown>:0:0: ran out of registers during register allocation in function 'hv_call_get_vp_registers'

[Philip Li]

On Mon, Aug 25, 2025 at 10:00:51AM -0700, Nathan Chancellor wrote:
> Hi Naman,
> 
> On Sun, Aug 24, 2025 at 11:13:51PM +0530, Naman Jain wrote:
> > 
> > 
> > On 8/24/2025 12:02 PM, kernel test robot wrote:
> > > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
> > > head:   0f4c93f7eb861acab537dbe94441817a270537bf
> > > commit: 96a1d2495c2f48467a91b8657bd594350b84ea9e [3139/4234] Drivers: hv: Introduce mshv_vtl driver
> > > config: i386-buildonly-randconfig-2003-20250824 (https://download.01.org/0day-ci/archive/20250824/202508240828.pVaUV45D-lkp@intel.com/config)
> > > compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
> > > reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250824/202508240828.pVaUV45D-lkp@intel.com/reproduce)
> > > 
> > > If you fix the issue in a separate patch/commit (i.e. not just a new version of
> > > the same patch/commit), kindly add following tags
> > > | Reported-by: kernel test robot <lkp@intel.com>
> > > | Closes: https://lore.kernel.org/oe-kbuild-all/202508240828.pVaUV45D-lkp@intel.com/
> > > 
> > > All errors (new ones prefixed by >>):
> > > 
> > > > > error: <unknown>:0:0: ran out of registers during register allocation in function 'hv_call_get_vp_registers'
> > > > > error: <unknown>:0:0: ran out of registers during register allocation in function 'hv_call_set_vp_registers'
> > > > > error: <unknown>:0:0: ran out of registers during register allocation in function 'hv_call_get_partition_property'
> > >     3 errors generated.
> > > 
> > 
> > +Nathan
> > 
> > I can see a bunch of similar warnings previously reported, in different
> > functions, but could not find a fix for it, or if this
> > is a blocking error:
> > 
> > https://lore.kernel.org/all/?q=s%3A%22ran+out+of+registers+during+register+allocation%22
> > 
> > These all are reported on below 32 bit config, compiled with LLVM:
> > i386-buildonly-randconfig-*
> > 
> > Found previous comment from Nathan Chancellor, here, which seems to be
> > related to this error:
> > https://lore.kernel.org/all/20250507022649.GA1984217@ax162/
> > 
> > """
> > This configuration has CONFIG_MATOM=y, which does not really work well
> > with clang for this reason and some others that have come up in the
> > past. Given it is likely that nobody will care enough to fix this on the
> > LLVM side (since it is 32-bit), we should probably just block using
> > MATOM with CC_IS_CLANG, which Arnd and I had talked about at the last
> > ClangBuiltLinux meeting.
> > """
> > 
> > This gives me an impression that we can safely ignore these errors from
> > kernel test bot.
> > Requesting Nathan to please correct me if I am wrong.
> 
> Yes, this is all correct. I will try to pursue an actual kernel side fix
> for this in Kconfig but I think the Intel folks can also start ignoring
> these reports for ARCH=i386 and CONFIG_MATOM so that they do not get
> sent to other kernel developers for random changes.

Got it, thanks Nathan, we will ignore these issues to avoid further reports.

> 
> Cheers,
> Nathan
>