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Subject[jgunthorpe:vfio_reflck_cleanup 5/12] drivers/vfio/pci/vfio_pci.c:2218:2: warning: variable 'to_reset' is used uninitialized whenever 'for' loop exits because its condition is false
tree:   https://github.com/jgunthorpe/linux vfio_reflck_cleanup
head: 092133ba5f5e5101af30de3b9448693753131849
commit: 58e8550548d133d11ebdea41a627de87dacc4168 [5/12] vfio/pci: Change vfio_pci_try_bus_reset() to use the dev_set
config: x86_64-randconfig-a011-20210705 (attached as .config)
compiler: clang version 13.0.0 (https://github.com/llvm/llvm-project 873e8b96b1226d64e4f95083147d8592ba7bd5d8)
reproduce (this is a W=1 build):
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# install x86_64 cross compiling tool for clang build
# apt-get install binutils-x86-64-linux-gnu
# https://github.com/jgunthorpe/linux/commit/58e8550548d133d11ebdea41a627de87dacc4168
git remote add jgunthorpe https://github.com/jgunthorpe/linux
git fetch --no-tags jgunthorpe vfio_reflck_cleanup
git checkout 58e8550548d133d11ebdea41a627de87dacc4168
# save the attached .config to linux build tree
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=x86_64

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

>> drivers/vfio/pci/vfio_pci.c:2218:2: warning: variable 'to_reset' is used uninitialized whenever 'for' loop exits because its condition is false [-Wsometimes-uninitialized]
list_for_each_entry(cur, &dev_set->device_list, vdev.dev_set_list) {
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
include/linux/list.h:629:7: note: expanded from macro 'list_for_each_entry'
!list_entry_is_head(pos, head, member); \
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/vfio/pci/vfio_pci.c:2224:7: note: uninitialized use occurs here
if (!to_reset)
^~~~~~~~
drivers/vfio/pci/vfio_pci.c:2218:2: note: remove the condition if it is always true
list_for_each_entry(cur, &dev_set->device_list, vdev.dev_set_list) {
^
include/linux/list.h:629:7: note: expanded from macro 'list_for_each_entry'
!list_entry_is_head(pos, head, member); \
^
drivers/vfio/pci/vfio_pci.c:2196:34: note: initialize the variable 'to_reset' to silence this warning
struct vfio_pci_device *to_reset;
^
= NULL
1 warning generated.


vim +2218 drivers/vfio/pci/vfio_pci.c

2177
2178 /*
2179 * If a bus or slot reset is available for the provided device and:
2180 * - All of the devices affected by that bus or slot reset are unused
2181 * (!refcnt)
2182 * - At least one of the affected devices is marked dirty via
2183 * needs_reset (such as by lack of FLR support)
2184 * Then attempt to perform that bus or slot reset. Callers are required
2185 * to hold vdev->dev_set->lock, protecting the bus/slot reset group from
2186 * concurrent opens.
2187 *
2188 * NB: vfio-core considers a group to be viable even if some devices are
2189 * bound to drivers like pci-stub or pcieport. Here we require all devices
2190 * to be bound to vfio_pci since that's the only way we can be sure they
2191 * stay put.
2192 */
2193 static void vfio_pci_try_bus_reset(struct vfio_pci_device *vdev)
2194 {
2195 struct vfio_device_set *dev_set = vdev->vdev.dev_set;
2196 struct vfio_pci_device *to_reset;
2197 struct vfio_pci_device *cur;
2198 int ret;
2199
2200 if (pci_probe_reset_slot(vdev->pdev->slot) ||
2201 pci_probe_reset_bus(vdev->pdev->bus))
2202 return;
2203
2204 lockdep_assert_held(&vdev->vdev.dev_set->lock);
2205
2206 /* All VFIO devices have a closed FD */
2207 list_for_each_entry(cur, &dev_set->device_list, vdev.dev_set_list)
2208 if (cur->vdev.open_count)
2209 return;
2210
2211 /* All devices in the group to be reset need VFIO devices */
2212 if (vfio_pci_for_each_slot_or_bus(
2213 vdev->pdev, vfio_pci_check_all_devices_bound, dev_set,
2214 !pci_probe_reset_slot(vdev->pdev->slot)))
2215 return;
2216
2217 /* Does at least one need a reset? */
> 2218 list_for_each_entry(cur, &dev_set->device_list, vdev.dev_set_list) {
2219 if (cur->needs_reset) {
2220 to_reset = cur;
2221 break;
2222 }
2223 }
2224 if (!to_reset)
2225 return;
2226
2227 ret = pci_reset_bus(to_reset->pdev);
2228 if (ret)
2229 return;
2230
2231 list_for_each_entry(cur, &dev_set->device_list, vdev.dev_set_list) {
2232 cur->needs_reset = false;
2233
2234 if (cur != to_reset && !disable_idle_d3)
2235 vfio_pci_set_power_state(cur, PCI_D3hot);
2236 }
2237 }
2238

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
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