linux-kernel - RE: ERROR: modpost: "__pt_no_sw_bit" [drivers/iommu/generic_pt/fmt/iommu

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Message-ID: <BL1PR11MB5271B4C385F1205E98B8535B8C87A@BL1PR11MB5271.namprd11.prod.outlook.com>
Date: Tue, 6 Jan 2026 08:09:27 +0000
From: "Tian, Kevin" <kevin.tian@...el.com>
To: lkp <lkp@...el.com>, Jason Gunthorpe <jgg@...dia.com>
CC: "oe-kbuild-all@...ts.linux.dev" <oe-kbuild-all@...ts.linux.dev>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Joerg Roedel
	<joerg.roedel@....com>
Subject: RE: ERROR: modpost: "__pt_no_sw_bit"
 [drivers/iommu/generic_pt/fmt/iommu_amdv1.ko] undefined!

> From: lkp <lkp@...el.com>
> Sent: Tuesday, December 23, 2025 7:25 AM
> 
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
> master
> head:   b927546677c876e26eba308550207c2ddf812a43
> commit: efa03dab7ce4ed786b131f412440e2fd45fba11f iommupt: Flush the
> CPU cache after any writes to the page table
> date:   7 weeks ago
> config: powerpc64-randconfig-r051-20251223
> (https://download.01.org/0day-
> ci/archive/20251223/202512230720.9y9DtWIo-lkp@...el.com/config)
> compiler: powerpc64-linux-gcc (GCC) 8.5.0
> reproduce (this is a W=1 build): (https://download.01.org/0day-
> ci/archive/20251223/202512230720.9y9DtWIo-lkp@...el.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@...el.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202512230720.9y9DtWIo-
> lkp@...el.com/
> 
> All errors (new ones prefixed by >>, old ones prefixed by <<):
> 
> >> ERROR: modpost: "__pt_no_sw_bit"
> [drivers/iommu/generic_pt/fmt/iommu_amdv1.ko] undefined!
> 

Jason, are you deliberately leaving it undefined to catch config which shouldn't
compile generic_pt in, or is it indeed a bug?

seems on x86 pt_feature() is inline built so all the reference to __pt_no_sw_bit
is removed statically due to:

        if (!PT_SUPPORTED_FEATURE(feature_nr))
                return false;

but ppc64 builds pt_feature() as an external symbol then hitting trouble on
undefined __pt_no_sw_bit...

Thanks
Kevin