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Date:   Mon, 29 Jun 2020 19:13:30 -0700 (PDT)
From:   David Rientjes <rientjes@google.com>
To:     Mike Rapoport <rppt@linux.ibm.com>
cc:     Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        kbuild-all@lists.01.org, linux-kernel@vger.kernel.org,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Subject: Re: ERROR: "min_low_pfn" undefined!
In-Reply-To: <202006300524.y9r1ZSHI%lkp@intel.com>
Message-ID: <alpine.DEB.2.22.394.2006291911220.1118534@chino.kir.corp.google.com>
References: <202006300524.y9r1ZSHI%lkp@intel.com>
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On Tue, 30 Jun 2020, kernel test robot wrote:

> Hi Alexander,
> 
> FYI, the error/warning still remains.
> 
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head:   7c30b859a947535f2213277e827d7ac7dcff9c84
> commit: f220df66f67684246ae1bf4a4e479efc7c2f325a intel_th: msu-sink: An example msu buffer "sink"
> date:   11 months ago
> config: microblaze-randconfig-c023-20200629 (attached as .config)
> compiler: microblaze-linux-gcc (GCC) 9.3.0
> 
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@intel.com>
> 
> All errors (new ones prefixed by >>):
> 
>    ERROR: "min_low_pfn" [drivers/rpmsg/virtio_rpmsg_bus.ko] undefined!
> >> ERROR: "min_low_pfn" [drivers/hwtracing/intel_th/intel_th_msu_sink.ko] undefined!
>    ERROR: "min_low_pfn" [drivers/hwtracing/intel_th/intel_th_msu.ko] undefined!
>    ERROR: "min_low_pfn" [drivers/mmc/core/mmc_core.ko] undefined!
>    ERROR: "min_low_pfn" [drivers/md/dm-crypt.ko] undefined!
>    ERROR: "min_low_pfn" [drivers/net/wireless/ath/ath6kl/ath6kl_sdio.ko] undefined!
>    ERROR: "min_low_pfn" [crypto/tcrypt.ko] undefined!
>    ERROR: "min_low_pfn" [crypto/asymmetric_keys/asym_tpm.ko] undefined!
> 

Looks like we have precedence for min_low_pfn failures and we can't blame 
this poor commit :)

I wonder why we don't simply do EXPORT_SYMBOL() in mm/memblock.c, 
non-microblaze architectures do this themselves because it doesn't get 
generically exported:

arch/ia64/kernel/ia64_ksyms.c:EXPORT_SYMBOL(min_low_pfn);       /* defined by bootmem.c, but not exported by generic code */
arch/sh/kernel/sh_ksyms_32.c:EXPORT_SYMBOL(min_low_pfn);

Adding Mike Rapoport.