Re: [PATCH v3 2/5] iommu/amd: Introduce helper functions to access and update 256-bit DTE

[kernel test robot]

Hi Suravee,

kernel test robot noticed the following build warnings:

[auto build test WARNING on linus/master]
[also build test WARNING on joro-iommu/next v6.11-rc6 next-20240906]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Suravee-Suthikulpanit/iommu-amd-Disable-AMD-IOMMU-if-CMPXCHG16B-feature-is-not-supported/20240906-201533
base:   linus/master
patch link:    https://lore.kernel.org/r/20240906121308.5013-3-suravee.suthikulpanit%40amd.com
patch subject: [PATCH v3 2/5] iommu/amd: Introduce helper functions to access and update 256-bit DTE
config: x86_64-rhel-8.3-rust (https://download.01.org/0day-ci/archive/20240907/202409072100.WaB846Yg-lkp@xxxxxxxxx/config)
compiler: clang version 18.1.5 (https://github.com/llvm/llvm-project 617a15a9eac96088ae5e9134248d8236e34b91b1)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240907/202409072100.WaB846Yg-lkp@xxxxxxxxx/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@xxxxxxxxx>
| Closes: https://lore.kernel.org/oe-kbuild-all/202409072100.WaB846Yg-lkp@xxxxxxxxx/

All warnings (new ones prefixed by >>):

>> drivers/iommu/amd/iommu.c:299:6: warning: variable 'ret' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
     299 |         if (!alias_data) {
         |             ^~~~~~~~~~~
   drivers/iommu/amd/iommu.c:309:9: note: uninitialized use occurs here
     309 |         return ret;
         |                ^~~
   drivers/iommu/amd/iommu.c:299:2: note: remove the 'if' if its condition is always true
     299 |         if (!alias_data) {
         |         ^~~~~~~~~~~~~~~~
   drivers/iommu/amd/iommu.c:279:9: note: initialize the variable 'ret' to silence this warning
     279 |         int ret;
         |                ^
         |                 = 0
   1 warning generated.


vim +299 drivers/iommu/amd/iommu.c

   272	
   273	static int clone_alias(struct pci_dev *pdev, u16 alias, void *data)
   274	{
   275		struct dev_table_entry dte;
   276		struct amd_iommu *iommu;
   277		struct iommu_dev_data *dev_data, *alias_data;
   278		u16 devid = pci_dev_id(pdev);
   279		int ret;
   280	
   281		if (devid == alias)
   282			return 0;
   283	
   284		iommu = rlookup_amd_iommu(&pdev->dev);
   285		if (!iommu)
   286			return 0;
   287	
   288		/* Get DTE for pdev */
   289		dev_data = dev_iommu_priv_get(&pdev->dev);
   290		if (!dev_data)
   291			return -EINVAL;
   292	
   293		spin_lock(&dev_data->dte_lock);
   294		get_dte256(iommu, dev_data, &dte);
   295		spin_unlock(&dev_data->dte_lock);
   296	
   297		/* Setup for alias */
   298		alias_data = search_dev_data(iommu, alias);
 > 299		if (!alias_data) {
   300			ret = -EINVAL;
   301			goto out;
   302		}
   303	
   304		spin_lock(&alias_data->dte_lock);
   305		update_dte256(iommu, alias_data, &dte);
   306		amd_iommu_set_rlookup_table(iommu, alias);
   307		spin_unlock(&alias_data->dte_lock);
   308	out:
   309		return ret;
   310	}
   311	

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