On 02/02/18 15:30, James Pearson wrote:

OK, I know CentOS has nothing to do with RHEL beta releases, but I wanted to test if el7.5 has added support for a particular peripheral (Wacom Pro 2 tablet) ... but was unable to install the propriety Nvidia display driver (v390.25) on a test workstation - and was wondering if anyone could explain on what is going on.

All I've done is upgrade an existing CentOS 7.4 install with the RHEL 7.5 beta kernel RPMS

However, when installing the Nvidia driver, it fails with:

FATAL: modpost: GPL-incompatible module nvidia.ko uses GPL-only symbol '__cachemode2pte_tbl'

A bit of Googling seems to suggest that this issue has been 'fixed' in later upstream kernels by changing the export of this symbol from 'EXPORT_SYMBOL_GPL' to 'EXPORT_SYMBOL'

However, 7.4 and earlier el7 kernels also export this symbol as EXPORT_SYMBOL_GPL - but the Nvidia driver builds/installs fine on 7.4 kernels ...

So, I'm not really sure what the issue is - i.e. is it an Nvidia or Redhat issue ?

It looks like a regression. This was originally fixed upstream (kernel.org) 3 years ago, so if the RHEL7.5 beta kernel has reverted to 'EXPORT_SYMBOL_GPL' then it is a regression that will break building any out-of-tree non-gpl modules which need to set caching mode in pte's

You should file a bug report with Red Hat.

For now, I've managed to hack around this by patching the stub Nvidia driver src to change MODULE_LICENSE from "NVIDIA" to "GPL" - and the Nvidia driver now installs and loads OK

The correct fix in the kernel is in arch/x86/mm/init.c

-EXPORT_SYMBOL_GPL(__cachemode2pte_tbl); +EXPORT_SYMBOL(__cachemode2pte_tbl);

If anyone knows any more about this, then please let me know

Thanks

James Pearson