Re: [PATCH v2 1/3] cpu/bugs: Allow forcing Automatic IBRS with SNP enabled using spectre_v2=eibrs
From: kernel test robot
Date: Wed Mar 11 2026 - 23:42:37 EST
Hi Kim,
kernel test robot noticed the following build warnings:
[auto build test WARNING on 7726ce2287804e70b2bf2fc00f104530b603d3f3]
url: https://github.com/intel-lab-lkp/linux/commits/Kim-Phillips/cpu-bugs-Allow-forcing-Automatic-IBRS-with-SNP-enabled-using-spectre_v2-eibrs/20260311-211730
base: 7726ce2287804e70b2bf2fc00f104530b603d3f3
patch link: https://lore.kernel.org/r/20260311130611.2201214-2-kim.phillips%40amd.com
patch subject: [PATCH v2 1/3] cpu/bugs: Allow forcing Automatic IBRS with SNP enabled using spectre_v2=eibrs
config: x86_64-randconfig-101-20260312 (https://download.01.org/0day-ci/archive/20260312/202603121136.bc8zNsHS-lkp@xxxxxxxxx/config)
compiler: gcc-14 (Debian 14.2.0-19) 14.2.0
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/202603121136.bc8zNsHS-lkp@xxxxxxxxx/
cocci warnings: (new ones prefixed by >>)
>> arch/x86/kernel/cpu/bugs.c:2190:42-44: WARNING !A || A && B is equivalent to !A || B
vim +2190 arch/x86/kernel/cpu/bugs.c
2122
2123 static void __init spectre_v2_select_mitigation(void)
2124 {
2125 if ((spectre_v2_cmd == SPECTRE_V2_CMD_RETPOLINE ||
2126 spectre_v2_cmd == SPECTRE_V2_CMD_RETPOLINE_LFENCE ||
2127 spectre_v2_cmd == SPECTRE_V2_CMD_RETPOLINE_GENERIC ||
2128 spectre_v2_cmd == SPECTRE_V2_CMD_EIBRS_LFENCE ||
2129 spectre_v2_cmd == SPECTRE_V2_CMD_EIBRS_RETPOLINE) &&
2130 !IS_ENABLED(CONFIG_MITIGATION_RETPOLINE)) {
2131 pr_err("RETPOLINE selected but not compiled in. Switching to AUTO select\n");
2132 spectre_v2_cmd = SPECTRE_V2_CMD_AUTO;
2133 }
2134
2135 if ((spectre_v2_cmd == SPECTRE_V2_CMD_EIBRS ||
2136 spectre_v2_cmd == SPECTRE_V2_CMD_EIBRS_LFENCE ||
2137 spectre_v2_cmd == SPECTRE_V2_CMD_EIBRS_RETPOLINE) &&
2138 !boot_cpu_has(X86_FEATURE_IBRS_ENHANCED)) {
2139 pr_err("EIBRS selected but CPU doesn't have Enhanced or Automatic IBRS. Switching to AUTO select\n");
2140 spectre_v2_cmd = SPECTRE_V2_CMD_AUTO;
2141 }
2142
2143 if ((spectre_v2_cmd == SPECTRE_V2_CMD_RETPOLINE_LFENCE ||
2144 spectre_v2_cmd == SPECTRE_V2_CMD_EIBRS_LFENCE) &&
2145 !boot_cpu_has(X86_FEATURE_LFENCE_RDTSC)) {
2146 pr_err("LFENCE selected, but CPU doesn't have a serializing LFENCE. Switching to AUTO select\n");
2147 spectre_v2_cmd = SPECTRE_V2_CMD_AUTO;
2148 }
2149
2150 if (spectre_v2_cmd == SPECTRE_V2_CMD_IBRS && !IS_ENABLED(CONFIG_MITIGATION_IBRS_ENTRY)) {
2151 pr_err("IBRS selected but not compiled in. Switching to AUTO select\n");
2152 spectre_v2_cmd = SPECTRE_V2_CMD_AUTO;
2153 }
2154
2155 if (spectre_v2_cmd == SPECTRE_V2_CMD_IBRS && boot_cpu_data.x86_vendor != X86_VENDOR_INTEL) {
2156 pr_err("IBRS selected but not Intel CPU. Switching to AUTO select\n");
2157 spectre_v2_cmd = SPECTRE_V2_CMD_AUTO;
2158 }
2159
2160 if (spectre_v2_cmd == SPECTRE_V2_CMD_IBRS && !boot_cpu_has(X86_FEATURE_IBRS)) {
2161 pr_err("IBRS selected but CPU doesn't have IBRS. Switching to AUTO select\n");
2162 spectre_v2_cmd = SPECTRE_V2_CMD_AUTO;
2163 }
2164
2165 if (spectre_v2_cmd == SPECTRE_V2_CMD_IBRS && cpu_feature_enabled(X86_FEATURE_XENPV)) {
2166 pr_err("IBRS selected but running as XenPV guest. Switching to AUTO select\n");
2167 spectre_v2_cmd = SPECTRE_V2_CMD_AUTO;
2168 }
2169
2170 if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2)) {
2171 spectre_v2_cmd = SPECTRE_V2_CMD_NONE;
2172 return;
2173 }
2174
2175 switch (spectre_v2_cmd) {
2176 case SPECTRE_V2_CMD_NONE:
2177 return;
2178
2179 case SPECTRE_V2_CMD_AUTO:
2180 if (!should_mitigate_vuln(X86_BUG_SPECTRE_V2))
2181 break;
2182 fallthrough;
2183 case SPECTRE_V2_CMD_FORCE:
2184 /*
2185 * Unless forced, don't use AutoIBRS when SNP is enabled
2186 * because it degrades host userspace indirect branch performance.
2187 */
2188 if (boot_cpu_has(X86_FEATURE_IBRS_ENHANCED) &&
2189 (!boot_cpu_has(X86_FEATURE_SEV_SNP) ||
> 2190 (boot_cpu_has(X86_FEATURE_SEV_SNP) &&
2191 spectre_v2_cmd == SPECTRE_V2_CMD_FORCE))) {
2192 spectre_v2_enabled = SPECTRE_V2_EIBRS;
2193 break;
2194 }
2195
2196 spectre_v2_enabled = spectre_v2_select_retpoline();
2197 break;
2198
2199 case SPECTRE_V2_CMD_RETPOLINE_LFENCE:
2200 pr_err(SPECTRE_V2_LFENCE_MSG);
2201 spectre_v2_enabled = SPECTRE_V2_LFENCE;
2202 break;
2203
2204 case SPECTRE_V2_CMD_RETPOLINE_GENERIC:
2205 spectre_v2_enabled = SPECTRE_V2_RETPOLINE;
2206 break;
2207
2208 case SPECTRE_V2_CMD_RETPOLINE:
2209 spectre_v2_enabled = spectre_v2_select_retpoline();
2210 break;
2211
2212 case SPECTRE_V2_CMD_IBRS:
2213 spectre_v2_enabled = SPECTRE_V2_IBRS;
2214 break;
2215
2216 case SPECTRE_V2_CMD_EIBRS:
2217 spectre_v2_enabled = SPECTRE_V2_EIBRS;
2218 break;
2219
2220 case SPECTRE_V2_CMD_EIBRS_LFENCE:
2221 spectre_v2_enabled = SPECTRE_V2_EIBRS_LFENCE;
2222 break;
2223
2224 case SPECTRE_V2_CMD_EIBRS_RETPOLINE:
2225 spectre_v2_enabled = SPECTRE_V2_EIBRS_RETPOLINE;
2226 break;
2227 }
2228 }
2229
--
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https://github.com/intel/lkp-tests/wiki