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 <philip.li@intel.com>]

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
>