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 <nathan@kernel.org>]

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