Re: [PATCH v2 1/3] cpu/bugs: Allow forcing Automatic IBRS with SNP enabled using spectre_v2=eibrs

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

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@intel.com/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@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202603121136.bc8zNsHS-lkp@intel.com/

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