The code needs some rethinking. The initialization of disp_path to NULL on line 2113 is not useful. disp_path will never be NULL after the list_for_each_entry_safe. The NULL errors are due to the impact of the failure of the disp_path test on line 2119, but that will never actually fail, so the problem is not there. julia ---------- Forwarded message ---------- Date: Tue, 9 Feb 2021 20:55:13 +0800 From: kernel test robot <lkp(a)intel.com&gt; To: kbuild(a)lists.01.org Cc: lkp(a)intel.com, Julia Lawall <julia.lawall(a)lip6.fr&gt; Subject: [intel-linux-intel-lts:5.4/yocto 8/24] drivers/gpu/drm/i915/gvt/display.c:2137:21-23: ERROR: disp_path is NULL but dereferenced. CC: kbuild-all(a)lists.01.org TO: Colin Xu <colin.xu(a)intel.com&gt; CC: "Qin, Chao" <chao.qin(a)intel.com&gt; CC: Hang Yuan <hang.yuan(a)intel.com&gt; tree: https://github.com/intel/linux-intel-lts.git 5.4/yocto head: 8bbfe55bfdb2905c35914605bc1b4a4404d86649 commit: 2521b097a48688b899e3db9cb855aa1ec59b02e8 [8/24] drm/i915/gvt: Rebase IDV 2.1 direct display to 5.4.x. :::::: branch date: 8 months ago :::::: commit date: 8 months ago config: x86_64-randconfig-c002-20210209 (attached as .config) compiler: gcc-9 (Debian 9.3.0-15) 9.3.0 If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; Reported-by: Julia Lawall <julia.lawall(a)lip6.fr&gt; "coccinelle warnings: (new ones prefixed by >>)" drivers/gpu/drm/i915/gvt/display.c:2138:31-37: ERROR: disp_path is NULL but dereferenced. drivers/gpu/drm/i915/gvt/display.c:2139:31-37: ERROR: disp_path is NULL but dereferenced. drivers/gpu/drm/i915/gvt/display.c:2140:21-31: ERROR: disp_path is NULL but dereferenced. drivers/gpu/drm/i915/gvt/display.c:2141:21-37: ERROR: disp_path is NULL but dereferenced. -- -- drivers/gpu/drm/i915/gvt/display.c:2119:39-48: ERROR: invalid reference to the index variable of the iterator on line 2114 drivers/gpu/drm/i915/gvt/display.c:2120:8-17: ERROR: invalid reference to the index variable of the iterator on line 2114 drivers/gpu/drm/i915/gvt/display.c:2121:9-18: ERROR: invalid reference to the index variable of the iterator on line 2114 drivers/gpu/drm/i915/gvt/display.c:1611:6-15: ERROR: invalid reference to the index variable of the iterator on line 1607 drivers/gpu/drm/i915/gvt/display.c:1798:6-15: ERROR: invalid reference to the index variable of the iterator on line 1794 drivers/gpu/drm/i915/gvt/display.c:1223:6-15: ERROR: invalid reference to the index variable of the iterator on line 1219 vim +2137 drivers/gpu/drm/i915/gvt/display.c 2521b097a48688 Colin Xu 2020-04-14 2071 2521b097a48688 Colin Xu 2020-04-14 2072 static void intel_gvt_switch_display_work(struct work_struct *w) 2521b097a48688 Colin Xu 2020-04-14 2073 { 2521b097a48688 Colin Xu 2020-04-14 2074 struct intel_gvt *gvt = container_of(w, 2521b097a48688 Colin Xu 2020-04-14 2075 struct intel_gvt, switch_display_work); 2521b097a48688 Colin Xu 2020-04-14 2076 struct intel_vgpu *vgpu, *old_v, *new_v; 2521b097a48688 Colin Xu 2020-04-14 2077 struct intel_vgpu_display_path *disp_path = NULL, *n; 2521b097a48688 Colin Xu 2020-04-14 2078 int id, old, new; 2521b097a48688 Colin Xu 2020-04-14 2079 u32 new_owner = 0; 2521b097a48688 Colin Xu 2020-04-14 2080 enum pipe pipe; 2521b097a48688 Colin Xu 2020-04-14 2081 enum port port; 2521b097a48688 Colin Xu 2020-04-14 2082 bool do_switch = false; 2521b097a48688 Colin Xu 2020-04-14 2083 2521b097a48688 Colin Xu 2020-04-14 2084 mutex_lock(&gvt->lock); 2521b097a48688 Colin Xu 2020-04-14 2085 mutex_lock(&gvt->sw_in_progress); 2521b097a48688 Colin Xu 2020-04-14 2086 2521b097a48688 Colin Xu 2020-04-14 2087 /* Switch base on port */ 2521b097a48688 Colin Xu 2020-04-14 2088 for_each_pipe(gvt->dev_priv, pipe) { 2521b097a48688 Colin Xu 2020-04-14 2089 port = intel_gvt_port_from_pipe(gvt->dev_priv, pipe); 2521b097a48688 Colin Xu 2020-04-14 2090 2521b097a48688 Colin Xu 2020-04-14 2091 if (port == PORT_NONE) 2521b097a48688 Colin Xu 2020-04-14 2092 continue; 2521b097a48688 Colin Xu 2020-04-14 2093 2521b097a48688 Colin Xu 2020-04-14 2094 gvt_dbg_dpy("Check display switch on PIPE_%c, PORT_%c\n", 2521b097a48688 Colin Xu 2020-04-14 2095 pipe_name(pipe), port_name(port)); 2521b097a48688 Colin Xu 2020-04-14 2096 2521b097a48688 Colin Xu 2020-04-14 2097 old = gvt->pipe_info[pipe].owner; 2521b097a48688 Colin Xu 2020-04-14 2098 new = (gvt->disp_owner >> port * 4) & 0xF; 2521b097a48688 Colin Xu 2020-04-14 2099 2521b097a48688 Colin Xu 2020-04-14 2100 old_v = NULL; 2521b097a48688 Colin Xu 2020-04-14 2101 new_v = NULL; 2521b097a48688 Colin Xu 2020-04-14 2102 do_switch = false; 2521b097a48688 Colin Xu 2020-04-14 2103 // Get old and new owners, either host or vGPU-x 2521b097a48688 Colin Xu 2020-04-14 2104 idr_for_each_entry((&(gvt)->vgpu_idr), vgpu, id) { 2521b097a48688 Colin Xu 2020-04-14 2105 if (old && id == old) 2521b097a48688 Colin Xu 2020-04-14 2106 old_v = vgpu; 2521b097a48688 Colin Xu 2020-04-14 2107 if (new && id == new) 2521b097a48688 Colin Xu 2020-04-14 2108 new_v = vgpu; 2521b097a48688 Colin Xu 2020-04-14 2109 } 2521b097a48688 Colin Xu 2020-04-14 2110 2521b097a48688 Colin Xu 2020-04-14 2111 if (new != old) { 2521b097a48688 Colin Xu 2020-04-14 2112 if (new_v) { 2521b097a48688 Colin Xu 2020-04-14 2113 disp_path = NULL; 2521b097a48688 Colin Xu 2020-04-14 2114 list_for_each_entry_safe(disp_path, n, &new_v->disp_cfg.path_list, list) { 2521b097a48688 Colin Xu 2020-04-14 2115 if (disp_path->p_pipe != INVALID_PIPE && 2521b097a48688 Colin Xu 2020-04-14 2116 disp_path->p_port == port) 2521b097a48688 Colin Xu 2020-04-14 2117 break; 2521b097a48688 Colin Xu 2020-04-14 2118 } 2521b097a48688 Colin Xu 2020-04-14 2119 if (atomic_read(&new_v->active) && disp_path && 2521b097a48688 Colin Xu 2020-04-14 2120 disp_path->foreground && 2521b097a48688 Colin Xu 2020-04-14 2121 !disp_path->foreground_state) { 2521b097a48688 Colin Xu 2020-04-14 2122 do_switch = true; 2521b097a48688 Colin Xu 2020-04-14 2123 gvt_dbg_dpy("Switch display to vGPU-%d, path-%d, PIPE_%c, PORT_%c\n", 2521b097a48688 Colin Xu 2020-04-14 2124 new_v->id, disp_path->id, 2521b097a48688 Colin Xu 2020-04-14 2125 pipe_name(disp_path->p_pipe), 2521b097a48688 Colin Xu 2020-04-14 2126 port_name(disp_path->p_port)); 2521b097a48688 Colin Xu 2020-04-14 2127 } else { 2521b097a48688 Colin Xu 2020-04-14 2128 // If can't switch to new vGPU, 2521b097a48688 Colin Xu 2020-04-14 2129 // maintain old owner. 2521b097a48688 Colin Xu 2020-04-14 2130 new_owner = gvt->disp_owner; 2521b097a48688 Colin Xu 2020-04-14 2131 new_owner &= ~(0xF << port * 4); 2521b097a48688 Colin Xu 2020-04-14 2132 new_owner |= (old << port * 4); 2521b097a48688 Colin Xu 2020-04-14 2133 gvt->disp_owner = new_owner; 2521b097a48688 Colin Xu 2020-04-14 2134 do_switch = false; 2521b097a48688 Colin Xu 2020-04-14 2135 gvt_dbg_dpy("Can't switch display to vGPU-%d active-%d, path-%d, PIPE_%c, PORT_%c, foreground-%d, foreground_state-%d\n", 2521b097a48688 Colin Xu 2020-04-14 2136 new_v->id, atomic_read(&new_v->active), 2521b097a48688 Colin Xu 2020-04-14 @2137 disp_path->id, 2521b097a48688 Colin Xu 2020-04-14 2138 pipe_name(disp_path->p_pipe), 2521b097a48688 Colin Xu 2020-04-14 2139 port_name(disp_path->p_port), 2521b097a48688 Colin Xu 2020-04-14 2140 disp_path->foreground, 2521b097a48688 Colin Xu 2020-04-14 2141 disp_path->foreground_state); 2521b097a48688 Colin Xu 2020-04-14 2142 } 2521b097a48688 Colin Xu 2020-04-14 2143 } else { 2521b097a48688 Colin Xu 2020-04-14 2144 // Switch to host is always expected possible 2521b097a48688 Colin Xu 2020-04-14 2145 do_switch = true; 2521b097a48688 Colin Xu 2020-04-14 2146 gvt_dbg_dpy("Switch display to host\n"); 2521b097a48688 Colin Xu 2020-04-14 2147 } 2521b097a48688 Colin Xu 2020-04-14 2148 } else { 2521b097a48688 Colin Xu 2020-04-14 2149 do_switch = false; 2521b097a48688 Colin Xu 2020-04-14 2150 gvt_dbg_dpy("Skip switch display due to unchanged owner\n"); 2521b097a48688 Colin Xu 2020-04-14 2151 } 2521b097a48688 Colin Xu 2020-04-14 2152 2521b097a48688 Colin Xu 2020-04-14 2153 if (do_switch && !prepare_for_switch_display(gvt, pipe)) { 2521b097a48688 Colin Xu 2020-04-14 2154 intel_gvt_switch_display_pipe(gvt, pipe, old_v, new_v); 2521b097a48688 Colin Xu 2020-04-14 2155 if (old_v && new_v) 2521b097a48688 Colin Xu 2020-04-14 2156 gvt_dbg_dpy("Change PIPE_%c PORT_%c owner from " 2521b097a48688 Colin Xu 2020-04-14 2157 "vGPU-%d to vGPU-%d\n", 2521b097a48688 Colin Xu 2020-04-14 2158 pipe_name(pipe), port_name(port), 2521b097a48688 Colin Xu 2020-04-14 2159 old_v->id, new_v->id); 2521b097a48688 Colin Xu 2020-04-14 2160 else if (old_v && !new_v) 2521b097a48688 Colin Xu 2020-04-14 2161 gvt_dbg_dpy("Change PIPE_%c PORT_%c owner from " 2521b097a48688 Colin Xu 2020-04-14 2162 "vGPU-%d to host\n", 2521b097a48688 Colin Xu 2020-04-14 2163 pipe_name(pipe), port_name(port), 2521b097a48688 Colin Xu 2020-04-14 2164 old_v->id); 2521b097a48688 Colin Xu 2020-04-14 2165 else if (!old_v && new_v) 2521b097a48688 Colin Xu 2020-04-14 2166 gvt_dbg_dpy("Change PIPE_%c PORT_%c owner from " 2521b097a48688 Colin Xu 2020-04-14 2167 "host to vGPU-%d\n", 2521b097a48688 Colin Xu 2020-04-14 2168 pipe_name(pipe), port_name(port), 2521b097a48688 Colin Xu 2020-04-14 2169 new_v->id); 2521b097a48688 Colin Xu 2020-04-14 2170 else 2521b097a48688 Colin Xu 2020-04-14 2171 gvt_dbg_dpy("Unexpected change PIPE_%c PORT_%c " 2521b097a48688 Colin Xu 2020-04-14 2172 "owner from host to host\n", 2521b097a48688 Colin Xu 2020-04-14 2173 pipe_name(pipe), port_name(port)); 2521b097a48688 Colin Xu 2020-04-14 2174 } 2521b097a48688 Colin Xu 2020-04-14 2175 } 2521b097a48688 Colin Xu 2020-04-14 2176 2521b097a48688 Colin Xu 2020-04-14 2177 mutex_unlock(&gvt->sw_in_progress); 2521b097a48688 Colin Xu 2020-04-14 2178 mutex_unlock(&gvt->lock); 2521b097a48688 Colin Xu 2020-04-14 2179 } 2521b097a48688 Colin Xu 2020-04-14 2180 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org