linux-kernel - Re: [PATCH 2/4 v5] cxl/core: Add helpers to detect Low Memory Holes on x86

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Message-ID: <5072006.vqk35OSZvh@fdefranc-mobl3>
Date: Wed, 05 Nov 2025 19:11:25 +0100
From: "Fabio M. De Francesco" <fabio.m.de.francesco@...ux.intel.com>
To: linux-cxl@...r.kernel.org, kernel test robot <lkp@...el.com>
Cc: oe-kbuild-all@...ts.linux.dev, Davidlohr Bueso <dave@...olabs.net>,
 Jonathan Cameron <jonathan.cameron@...wei.com>,
 Dave Jiang <dave.jiang@...el.com>,
 Alison Schofield <alison.schofield@...el.com>,
 Vishal Verma <vishal.l.verma@...el.com>, Ira Weiny <ira.weiny@...el.com>,
 Dan Williams <dan.j.williams@...el.com>, Jonathan Corbet <corbet@....net>,
 linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
 Gregory Price <gourry@...rry.net>, Robert Richter <rrichter@....com>,
 Cheatham Benjamin <benjamin.cheatham@....com>
Subject:
 Re: [PATCH 2/4 v5] cxl/core: Add helpers to detect Low Memory Holes on x86

On Friday, October 10, 2025 9:38:02 AM Central European Standard Time kernel test robot wrote:
> Hi Fabio,
> 
> kernel test robot noticed the following build errors:
> 
> [auto build test ERROR on 46037455cbb748c5e85071c95f2244e81986eb58]
> 
> url:    https://github.com/intel-lab-lkp/linux/commits/Fabio-M-De-Francesco/cxl-core-Change-match_-_by_range-signatures/20251010-111627
> base:   46037455cbb748c5e85071c95f2244e81986eb58
> patch link:    https://lore.kernel.org/r/20251006155836.791418-3-fabio.m.de.francesco%40linux.intel.com
> patch subject: [PATCH 2/4 v5] cxl/core: Add helpers to detect Low Memory Holes on x86
> config: i386-buildonly-randconfig-005-20251010 (https://download.01.org/0day-ci/archive/20251010/202510101555.zofjGvZF-lkp@intel.com/config)
> compiler: gcc-14 (Debian 14.2.0-19) 14.2.0
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251010/202510101555.zofjGvZF-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@...el.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202510101555.zofjGvZF-lkp@intel.com/
> 
> All errors (new ones prefixed by >>):
> 
>    ld: drivers/cxl/core/platform_quirks.o: in function `platform_res_adjust':
> >> drivers/cxl/core/platform_quirks.c:95:(.text+0x1f1): undefined reference to `__udivdi3'
> 
> 
> vim +95 drivers/cxl/core/platform_quirks.c
> 
>     76	
>     77	void platform_res_adjust(struct resource *res,
>     78				 struct cxl_endpoint_decoder *cxled,
>     79				 const struct cxl_root_decoder *cxlrd)
>     80	{
>     81		if (!platform_cxlrd_matches_cxled(cxlrd, cxled))
>     82			return;
>     83	
>     84		guard(rwsem_write)(&cxl_rwsem.dpa);
>     85		dev_dbg(cxled_to_memdev(cxled)->dev.parent,
>     86			"Low Memory Hole detected. Resources were (%s: %pr, %pr)\n",
>     87			dev_name(&cxled->cxld.dev), res, cxled->dpa_res);
>     88		if (res) {
>     89			/* Trim region resource overlap with LMH */
>     90			res->end = cxlrd->res->end;
>     91		}
>     92		/* Match endpoint decoder's DPA resource to root decoder's */
>     93		cxled->dpa_res->end =
>     94			cxled->dpa_res->start +
>   > 95			resource_size(cxlrd->res) / cxled->cxld.interleave_ways - 1;
> 
I think that the use of udiv_64() (per Alison suggestion) will fix this 
error.

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