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[PATCH v5 4/9] x86/vmscape: Move mitigation selection to a switch()

Pawan Gupta posted 9 patches 5 days ago
[PATCH v5 4/9] x86/vmscape: Move mitigation selection to a switch()
Posted by Pawan Gupta 5 days ago 
This ensures that all mitigation modes are explicitly handled, while
keeping the mitigation selection for each mode together. This also prepares
for adding BHB-clearing mitigation mode for VMSCAPE.

Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
---
 arch/x86/kernel/cpu/bugs.c | 23 +++++++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 1e9b11198db0fe2483bd17b1327bcfd44a2c1dbf..ecefea3c018117031ea1d1ef8f4fca6e425a936c 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -3231,17 +3231,32 @@ early_param("vmscape", vmscape_parse_cmdline);
 
 static void __init vmscape_select_mitigation(void)
 {
-	if (!boot_cpu_has_bug(X86_BUG_VMSCAPE) ||
-	    !boot_cpu_has(X86_FEATURE_IBPB)) {
+	if (!boot_cpu_has_bug(X86_BUG_VMSCAPE)) {
 		vmscape_mitigation = VMSCAPE_MITIGATION_NONE;
 		return;
 	}
 
-	if (vmscape_mitigation == VMSCAPE_MITIGATION_AUTO) {
-		if (should_mitigate_vuln(X86_BUG_VMSCAPE))
+	if ((vmscape_mitigation == VMSCAPE_MITIGATION_AUTO) &&
+	    !should_mitigate_vuln(X86_BUG_VMSCAPE))
+		vmscape_mitigation = VMSCAPE_MITIGATION_NONE;
+
+	switch (vmscape_mitigation) {
+	case VMSCAPE_MITIGATION_NONE:
+		break;
+
+	case VMSCAPE_MITIGATION_IBPB_EXIT_TO_USER:
+		if (!boot_cpu_has(X86_FEATURE_IBPB))
+			vmscape_mitigation = VMSCAPE_MITIGATION_NONE;
+		break;
+
+	case VMSCAPE_MITIGATION_AUTO:
+		if (boot_cpu_has(X86_FEATURE_IBPB))
 			vmscape_mitigation = VMSCAPE_MITIGATION_IBPB_EXIT_TO_USER;
 		else
 			vmscape_mitigation = VMSCAPE_MITIGATION_NONE;
+		break;
+
+	default:
 	}
 }
 

-- 
2.34.1
Re: [PATCH v5 4/9] x86/vmscape: Move mitigation selection to a switch()
Posted by kernel test robot 2 days, 3 hours ago 
Hi Pawan,

kernel test robot noticed the following build warnings:

[auto build test WARNING on 6a23ae0a96a600d1d12557add110e0bb6e32730c]

url:    https://github.com/intel-lab-lkp/linux/commits/Pawan-Gupta/x86-bhi-x86-vmscape-Move-LFENCE-out-of-clear_bhb_loop/20251127-061843
base:   6a23ae0a96a600d1d12557add110e0bb6e32730c
patch link:    https://lore.kernel.org/r/20251126-vmscape-bhb-v5-4-02d66e423b00%40linux.intel.com
patch subject: [PATCH v5 4/9] x86/vmscape: Move mitigation selection to a switch()
config: x86_64-randconfig-122-20251129 (https://download.01.org/0day-ci/archive/20251130/202511300322.KCG4AuJ9-lkp@intel.com/config)
compiler: gcc-13 (Debian 13.3.0-16) 13.3.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251130/202511300322.KCG4AuJ9-lkp@intel.com/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@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202511300322.KCG4AuJ9-lkp@intel.com/

sparse warnings: (new ones prefixed by >>)
>> arch/x86/kernel/cpu/bugs.c:3260:9: sparse: sparse: statement expected after case label

vim +3260 arch/x86/kernel/cpu/bugs.c

556c1ad666ad90 Pawan Gupta  2025-08-14  3231  
556c1ad666ad90 Pawan Gupta  2025-08-14  3232  static void __init vmscape_select_mitigation(void)
556c1ad666ad90 Pawan Gupta  2025-08-14  3233  {
0091dd36e9ee51 Pawan Gupta  2025-11-26  3234  	if (!boot_cpu_has_bug(X86_BUG_VMSCAPE)) {
556c1ad666ad90 Pawan Gupta  2025-08-14  3235  		vmscape_mitigation = VMSCAPE_MITIGATION_NONE;
556c1ad666ad90 Pawan Gupta  2025-08-14  3236  		return;
556c1ad666ad90 Pawan Gupta  2025-08-14  3237  	}
556c1ad666ad90 Pawan Gupta  2025-08-14  3238  
0091dd36e9ee51 Pawan Gupta  2025-11-26  3239  	if ((vmscape_mitigation == VMSCAPE_MITIGATION_AUTO) &&
0091dd36e9ee51 Pawan Gupta  2025-11-26  3240  	    !should_mitigate_vuln(X86_BUG_VMSCAPE))
0091dd36e9ee51 Pawan Gupta  2025-11-26  3241  		vmscape_mitigation = VMSCAPE_MITIGATION_NONE;
0091dd36e9ee51 Pawan Gupta  2025-11-26  3242  
0091dd36e9ee51 Pawan Gupta  2025-11-26  3243  	switch (vmscape_mitigation) {
0091dd36e9ee51 Pawan Gupta  2025-11-26  3244  	case VMSCAPE_MITIGATION_NONE:
0091dd36e9ee51 Pawan Gupta  2025-11-26  3245  		break;
0091dd36e9ee51 Pawan Gupta  2025-11-26  3246  
0091dd36e9ee51 Pawan Gupta  2025-11-26  3247  	case VMSCAPE_MITIGATION_IBPB_EXIT_TO_USER:
0091dd36e9ee51 Pawan Gupta  2025-11-26  3248  		if (!boot_cpu_has(X86_FEATURE_IBPB))
0091dd36e9ee51 Pawan Gupta  2025-11-26  3249  			vmscape_mitigation = VMSCAPE_MITIGATION_NONE;
0091dd36e9ee51 Pawan Gupta  2025-11-26  3250  		break;
0091dd36e9ee51 Pawan Gupta  2025-11-26  3251  
0091dd36e9ee51 Pawan Gupta  2025-11-26  3252  	case VMSCAPE_MITIGATION_AUTO:
0091dd36e9ee51 Pawan Gupta  2025-11-26  3253  		if (boot_cpu_has(X86_FEATURE_IBPB))
556c1ad666ad90 Pawan Gupta  2025-08-14  3254  			vmscape_mitigation = VMSCAPE_MITIGATION_IBPB_EXIT_TO_USER;
5799d5d8a6c877 David Kaplan 2025-09-12  3255  		else
5799d5d8a6c877 David Kaplan 2025-09-12  3256  			vmscape_mitigation = VMSCAPE_MITIGATION_NONE;
0091dd36e9ee51 Pawan Gupta  2025-11-26  3257  		break;
0091dd36e9ee51 Pawan Gupta  2025-11-26  3258  
0091dd36e9ee51 Pawan Gupta  2025-11-26  3259  	default:
5799d5d8a6c877 David Kaplan 2025-09-12 @3260  	}
556c1ad666ad90 Pawan Gupta  2025-08-14  3261  }
556c1ad666ad90 Pawan Gupta  2025-08-14  3262  

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
Re: [PATCH v5 4/9] x86/vmscape: Move mitigation selection to a switch()
Posted by kernel test robot 4 days, 21 hours ago 
Hi Pawan,

kernel test robot noticed the following build warnings:

[auto build test WARNING on 6a23ae0a96a600d1d12557add110e0bb6e32730c]

url:    https://github.com/intel-lab-lkp/linux/commits/Pawan-Gupta/x86-bhi-x86-vmscape-Move-LFENCE-out-of-clear_bhb_loop/20251127-061843
base:   6a23ae0a96a600d1d12557add110e0bb6e32730c
patch link:    https://lore.kernel.org/r/20251126-vmscape-bhb-v5-4-02d66e423b00%40linux.intel.com
patch subject: [PATCH v5 4/9] x86/vmscape: Move mitigation selection to a switch()
config: x86_64-allnoconfig (https://download.01.org/0day-ci/archive/20251127/202511270829.xMEXUXCW-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251127/202511270829.xMEXUXCW-lkp@intel.com/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@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202511270829.xMEXUXCW-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> arch/x86/kernel/cpu/bugs.c:3260:2: warning: label at end of compound statement is a C23 extension [-Wc23-extensions]
    3260 |         }
         |         ^
   1 warning generated.


vim +3260 arch/x86/kernel/cpu/bugs.c

556c1ad666ad90 Pawan Gupta  2025-08-14  3231  
556c1ad666ad90 Pawan Gupta  2025-08-14  3232  static void __init vmscape_select_mitigation(void)
556c1ad666ad90 Pawan Gupta  2025-08-14  3233  {
0091dd36e9ee51 Pawan Gupta  2025-11-26  3234  	if (!boot_cpu_has_bug(X86_BUG_VMSCAPE)) {
556c1ad666ad90 Pawan Gupta  2025-08-14  3235  		vmscape_mitigation = VMSCAPE_MITIGATION_NONE;
556c1ad666ad90 Pawan Gupta  2025-08-14  3236  		return;
556c1ad666ad90 Pawan Gupta  2025-08-14  3237  	}
556c1ad666ad90 Pawan Gupta  2025-08-14  3238  
0091dd36e9ee51 Pawan Gupta  2025-11-26  3239  	if ((vmscape_mitigation == VMSCAPE_MITIGATION_AUTO) &&
0091dd36e9ee51 Pawan Gupta  2025-11-26  3240  	    !should_mitigate_vuln(X86_BUG_VMSCAPE))
0091dd36e9ee51 Pawan Gupta  2025-11-26  3241  		vmscape_mitigation = VMSCAPE_MITIGATION_NONE;
0091dd36e9ee51 Pawan Gupta  2025-11-26  3242  
0091dd36e9ee51 Pawan Gupta  2025-11-26  3243  	switch (vmscape_mitigation) {
0091dd36e9ee51 Pawan Gupta  2025-11-26  3244  	case VMSCAPE_MITIGATION_NONE:
0091dd36e9ee51 Pawan Gupta  2025-11-26  3245  		break;
0091dd36e9ee51 Pawan Gupta  2025-11-26  3246  
0091dd36e9ee51 Pawan Gupta  2025-11-26  3247  	case VMSCAPE_MITIGATION_IBPB_EXIT_TO_USER:
0091dd36e9ee51 Pawan Gupta  2025-11-26  3248  		if (!boot_cpu_has(X86_FEATURE_IBPB))
0091dd36e9ee51 Pawan Gupta  2025-11-26  3249  			vmscape_mitigation = VMSCAPE_MITIGATION_NONE;
0091dd36e9ee51 Pawan Gupta  2025-11-26  3250  		break;
0091dd36e9ee51 Pawan Gupta  2025-11-26  3251  
0091dd36e9ee51 Pawan Gupta  2025-11-26  3252  	case VMSCAPE_MITIGATION_AUTO:
0091dd36e9ee51 Pawan Gupta  2025-11-26  3253  		if (boot_cpu_has(X86_FEATURE_IBPB))
556c1ad666ad90 Pawan Gupta  2025-08-14  3254  			vmscape_mitigation = VMSCAPE_MITIGATION_IBPB_EXIT_TO_USER;
5799d5d8a6c877 David Kaplan 2025-09-12  3255  		else
5799d5d8a6c877 David Kaplan 2025-09-12  3256  			vmscape_mitigation = VMSCAPE_MITIGATION_NONE;
0091dd36e9ee51 Pawan Gupta  2025-11-26  3257  		break;
0091dd36e9ee51 Pawan Gupta  2025-11-26  3258  
0091dd36e9ee51 Pawan Gupta  2025-11-26  3259  	default:
5799d5d8a6c877 David Kaplan 2025-09-12 @3260  	}
556c1ad666ad90 Pawan Gupta  2025-08-14  3261  }
556c1ad666ad90 Pawan Gupta  2025-08-14  3262  

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Patchew 2.1-devel-b67e4c2

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