Re: [PATCH v3 2/2] x86/devmem: Drop /dev/mem access for confidential guests

[kernel test robot <lkp@intel.com>]

Hi Dan,

kernel test robot noticed the following build errors:

[auto build test ERROR on 0af2f6be1b4281385b618cb86ad946eded089ac8]

url:    https://github.com/intel-lab-lkp/linux/commits/Dan-Williams/x86-devmem-Remove-duplicate-range_is_allowed-definition/20250419-080713
base:   0af2f6be1b4281385b618cb86ad946eded089ac8
patch link:    https://lore.kernel.org/r/174491712829.1395340.5054725417641299524.stgit%40dwillia2-xfh.jf.intel.com
patch subject: [PATCH v3 2/2] x86/devmem: Drop /dev/mem access for confidential guests
config: openrisc-randconfig-r073-20250428 (https://download.01.org/0day-ci/archive/20250507/202505071309.Aa4vRJxa-lkp@intel.com/config)
compiler: or1k-linux-gcc (GCC) 10.5.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250507/202505071309.Aa4vRJxa-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/202505071309.Aa4vRJxa-lkp@intel.com/

All errors (new ones prefixed by >>):

   drivers/char/mem.c: In function 'open_port':
>> drivers/char/mem.c:604:6: error: implicit declaration of function 'cc_platform_has' [-Werror=implicit-function-declaration]
     604 |      cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT))
         |      ^~~~~~~~~~~~~~~
>> drivers/char/mem.c:604:22: error: 'CC_ATTR_GUEST_MEM_ENCRYPT' undeclared (first use in this function)
     604 |      cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT))
         |                      ^~~~~~~~~~~~~~~~~~~~~~~~~
   drivers/char/mem.c:604:22: note: each undeclared identifier is reported only once for each function it appears in
   cc1: some warnings being treated as errors


vim +/cc_platform_has +604 drivers/char/mem.c

   586	
   587	static int open_port(struct inode *inode, struct file *filp)
   588	{
   589		int rc;
   590	
   591		if (!capable(CAP_SYS_RAWIO))
   592			return -EPERM;
   593	
   594		rc = security_locked_down(LOCKDOWN_DEV_MEM);
   595		if (rc)
   596			return rc;
   597	
   598		/*
   599		 * Enforce encrypted mapping consistency and avoid unaccepted
   600		 * memory conflicts, "lockdown" /dev/mem for confidential
   601		 * guests.
   602		 */
   603		if (IS_ENABLED(CONFIG_STRICT_DEVMEM) &&
 > 604		    cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT))
   605			return -EPERM;
   606	
   607		if (iminor(inode) != DEVMEM_MINOR)
   608			return 0;
   609	
   610		/*
   611		 * Use a unified address space to have a single point to manage
   612		 * revocations when drivers want to take over a /dev/mem mapped
   613		 * range.
   614		 */
   615		filp->f_mapping = iomem_get_mapping();
   616	
   617		return 0;
   618	}
   619	

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