[kbuild-all] Re: [kvm:queue 71/177] arch/x86/kvm/vmx/nested.c:5246:3: error: variable 'roots_to_free' is used uninitialized whenever 'if' condition is false

tree: https://git.kernel.org/pub/scm/virt/kvm/kvm.git queue head: cb953129bfe5c0f2da835a0469930873fb7e71df commit: ce8fe7b77bd8ee405295e349c82d0ef8c9788200 [71/177] KVM: nVMX: Free only the affected contexts when emulating INVEPT config: x86_64-randconfig-a012-20200515 (attached as .config) compiler: clang version 11.0.0 (https://github.com/llvm/llvm-project 13d44b2a0c7ef404b13b16644765977cd5310fe2) reproduce: 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 git checkout ce8fe7b77bd8ee405295e349c82d0ef8c9788200 # 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: kbuild test robot <lkp(a)intel.com&gt; Note: the kvm/queue HEAD cb953129bfe5c0f2da835a0469930873fb7e71df builds fine. It only hurts bisectibility. All errors (new ones prefixed by >>, old ones prefixed by <<): >> arch/x86/kvm/vmx/nested.c:5246:3: error: variable 'roots_to_free' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized] BUG_ON(1); ^~~~~~~~~ include/asm-generic/bug.h:62:32: note: expanded from macro 'BUG_ON' #define BUG_ON(condition) do { if (unlikely(condition)) BUG(); } while (0) ^~~~~~~~~~~~~~~~~~~~~~~~ include/linux/compiler.h:56:28: note: expanded from macro 'if' #define if(cond, ...) if ( __trace_if_var( !!(cond , ## __VA_ARGS__) ) ) ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ include/linux/compiler.h:58:30: note: expanded from macro '__trace_if_var' #define __trace_if_var(cond) (__builtin_constant_p(cond) ? (cond) : __trace_if_value(cond)) ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ arch/x86/kvm/vmx/nested.c:5250:6: note: uninitialized use occurs here if (roots_to_free) ^~~~~~~~~~~~~ include/linux/compiler.h:56:47: note: expanded from macro 'if' #define if(cond, ...) if ( __trace_if_var( !!(cond , ## __VA_ARGS__) ) ) ^~~~ include/linux/compiler.h:58:52: note: expanded from macro '__trace_if_var' #define __trace_if_var(cond) (__builtin_constant_p(cond) ? (cond) : __trace_if_value(cond)) ^~~~ arch/x86/kvm/vmx/nested.c:5246:3: note: remove the 'if' if its condition is always true BUG_ON(1); ^ include/asm-generic/bug.h:62:32: note: expanded from macro 'BUG_ON' #define BUG_ON(condition) do { if (unlikely(condition)) BUG(); } while (0) ^ include/linux/compiler.h:56:23: note: expanded from macro 'if' #define if(cond, ...) if ( __trace_if_var( !!(cond , ## __VA_ARGS__) ) ) ^ arch/x86/kvm/vmx/nested.c:5179:35: note: initialize the variable 'roots_to_free' to silence this warning unsigned long type, roots_to_free; ^ = 0 1 error generated. vim +5246 arch/x86/kvm/vmx/nested.c ce8fe7b77bd8ee Sean Christopherson 2020-03-20 5173 55d2375e58a61b Sean Christopherson 2018-12-03 5174 /* Emulate the INVEPT instruction */ 55d2375e58a61b Sean Christopherson 2018-12-03 5175 static int handle_invept(struct kvm_vcpu *vcpu) 55d2375e58a61b Sean Christopherson 2018-12-03 5176 { 55d2375e58a61b Sean Christopherson 2018-12-03 5177 struct vcpu_vmx *vmx = to_vmx(vcpu); 55d2375e58a61b Sean Christopherson 2018-12-03 5178 u32 vmx_instruction_info, types; ce8fe7b77bd8ee Sean Christopherson 2020-03-20 5179 unsigned long type, roots_to_free;

ce8fe7b77bd8ee Sean Christopherson 2020-03-20 5180 struct kvm_mmu *mmu; 55d2375e58a61b Sean Christopherson 2018-12-03 5181 gva_t gva; 55d2375e58a61b Sean Christopherson 2018-12-03 5182 struct x86_exception e; 55d2375e58a61b Sean Christopherson 2018-12-03 5183 struct { 55d2375e58a61b Sean Christopherson 2018-12-03 5184 u64 eptp, gpa; 55d2375e58a61b Sean Christopherson 2018-12-03 5185 } operand; ce8fe7b77bd8ee Sean Christopherson 2020-03-20 5186 int i; 55d2375e58a61b Sean Christopherson 2018-12-03 5187 55d2375e58a61b Sean Christopherson 2018-12-03 5188 if (!(vmx->nested.msrs.secondary_ctls_high & 55d2375e58a61b Sean Christopherson 2018-12-03 5189 SECONDARY_EXEC_ENABLE_EPT) || 55d2375e58a61b Sean Christopherson 2018-12-03 5190 !(vmx->nested.msrs.ept_caps & VMX_EPT_INVEPT_BIT)) { 55d2375e58a61b Sean Christopherson 2018-12-03 5191 kvm_queue_exception(vcpu, UD_VECTOR); 55d2375e58a61b Sean Christopherson 2018-12-03 5192 return 1; 55d2375e58a61b Sean Christopherson 2018-12-03 5193 } 55d2375e58a61b Sean Christopherson 2018-12-03 5194 55d2375e58a61b Sean Christopherson 2018-12-03 5195 if (!nested_vmx_check_permission(vcpu)) 55d2375e58a61b Sean Christopherson 2018-12-03 5196 return 1; 55d2375e58a61b Sean Christopherson 2018-12-03 5197 55d2375e58a61b Sean Christopherson 2018-12-03 5198 vmx_instruction_info = vmcs_read32(VMX_INSTRUCTION_INFO); 55d2375e58a61b Sean Christopherson 2018-12-03 5199 type = kvm_register_readl(vcpu, (vmx_instruction_info >> 28) & 0xf); 55d2375e58a61b Sean Christopherson 2018-12-03 5200 55d2375e58a61b Sean Christopherson 2018-12-03 5201 types = (vmx->nested.msrs.ept_caps >> VMX_EPT_EXTENT_SHIFT) & 6; 55d2375e58a61b Sean Christopherson 2018-12-03 5202 55d2375e58a61b Sean Christopherson 2018-12-03 5203 if (type >= 32 || !(types & (1 << type))) 55d2375e58a61b Sean Christopherson 2018-12-03 5204 return nested_vmx_failValid(vcpu, 55d2375e58a61b Sean Christopherson 2018-12-03 5205 VMXERR_INVALID_OPERAND_TO_INVEPT_INVVPID); 55d2375e58a61b Sean Christopherson 2018-12-03 5206 55d2375e58a61b Sean Christopherson 2018-12-03 5207 /* According to the Intel VMX instruction reference, the memory 55d2375e58a61b Sean Christopherson 2018-12-03 5208 * operand is read even if it isn't needed (e.g., for type==global) 55d2375e58a61b Sean Christopherson 2018-12-03 5209 */ 55d2375e58a61b Sean Christopherson 2018-12-03 5210 if (get_vmx_mem_address(vcpu, vmcs_readl(EXIT_QUALIFICATION), fdb28619a8f033 Eugene Korenevsky 2019-06-06 5211 vmx_instruction_info, false, sizeof(operand), &gva)) 55d2375e58a61b Sean Christopherson 2018-12-03 5212 return 1; 55d2375e58a61b Sean Christopherson 2018-12-03 5213 if (kvm_read_guest_virt(vcpu, gva, &operand, sizeof(operand), &e)) { ee1fa209f5e5ca Junaid Shahid 2020-03-20 5214 kvm_inject_emulated_page_fault(vcpu, &e); 55d2375e58a61b Sean Christopherson 2018-12-03 5215 return 1; 55d2375e58a61b Sean Christopherson 2018-12-03 5216 } 55d2375e58a61b Sean Christopherson 2018-12-03 5217 ce8fe7b77bd8ee Sean Christopherson 2020-03-20 5218 /* ce8fe7b77bd8ee Sean Christopherson 2020-03-20 5219 * Nested EPT roots are always held through guest_mmu, ce8fe7b77bd8ee Sean Christopherson 2020-03-20 5220 * not root_mmu. ce8fe7b77bd8ee Sean Christopherson 2020-03-20 5221 */ ce8fe7b77bd8ee Sean Christopherson 2020-03-20 5222 mmu = &vcpu->arch.guest_mmu; ce8fe7b77bd8ee Sean Christopherson 2020-03-20 5223 55d2375e58a61b Sean Christopherson 2018-12-03 5224 switch (type) { b119019847fbca Jim Mattson 2019-06-13 5225 case VMX_EPT_EXTENT_CONTEXT: eed0030e4caa94 Sean Christopherson 2020-03-20 5226 if (!nested_vmx_check_eptp(vcpu, operand.eptp)) eed0030e4caa94 Sean Christopherson 2020-03-20 5227 return nested_vmx_failValid(vcpu, eed0030e4caa94 Sean Christopherson 2020-03-20 5228 VMXERR_INVALID_OPERAND_TO_INVEPT_INVVPID); f8aa7e3958bc43 Sean Christopherson 2020-03-20 5229 ce8fe7b77bd8ee Sean Christopherson 2020-03-20 5230 roots_to_free = 0;

ce8fe7b77bd8ee Sean Christopherson 2020-03-20 5231 if (nested_ept_root_matches(mmu->root_hpa, mmu->root_cr3, ce8fe7b77bd8ee Sean Christopherson 2020-03-20 5232 operand.eptp)) ce8fe7b77bd8ee Sean Christopherson 2020-03-20 5233 roots_to_free |= KVM_MMU_ROOT_CURRENT; ce8fe7b77bd8ee Sean Christopherson 2020-03-20 5234 ce8fe7b77bd8ee Sean Christopherson 2020-03-20 5235 for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++) { ce8fe7b77bd8ee Sean Christopherson 2020-03-20 5236 if (nested_ept_root_matches(mmu->prev_roots[i].hpa, ce8fe7b77bd8ee Sean Christopherson 2020-03-20 5237 mmu->prev_roots[i].cr3, ce8fe7b77bd8ee Sean Christopherson 2020-03-20 5238 operand.eptp)) ce8fe7b77bd8ee Sean Christopherson 2020-03-20 5239 roots_to_free |= KVM_MMU_ROOT_PREVIOUS(i); ce8fe7b77bd8ee Sean Christopherson 2020-03-20 5240 } ce8fe7b77bd8ee Sean Christopherson 2020-03-20 5241 break; eed0030e4caa94 Sean Christopherson 2020-03-20 5242 case VMX_EPT_EXTENT_GLOBAL: ce8fe7b77bd8ee Sean Christopherson 2020-03-20 5243 roots_to_free = KVM_MMU_ROOTS_ALL;

55d2375e58a61b Sean Christopherson 2018-12-03 5244 break; 55d2375e58a61b Sean Christopherson 2018-12-03 5245 default: 55d2375e58a61b Sean Christopherson 2018-12-03 @5246 BUG_ON(1); 55d2375e58a61b Sean Christopherson 2018-12-03 5247 break; 55d2375e58a61b Sean Christopherson 2018-12-03 5248 } 55d2375e58a61b Sean Christopherson 2018-12-03 5249 ce8fe7b77bd8ee Sean Christopherson 2020-03-20 5250 if (roots_to_free)

ce8fe7b77bd8ee Sean Christopherson 2020-03-20 5251 kvm_mmu_free_roots(vcpu, mmu, roots_to_free); ce8fe7b77bd8ee Sean Christopherson 2020-03-20 5252 55d2375e58a61b Sean Christopherson 2018-12-03 5253 return nested_vmx_succeed(vcpu); 55d2375e58a61b Sean Christopherson 2018-12-03 5254 } 55d2375e58a61b Sean Christopherson 2018-12-03 5255 :::::: The code at line 5246 was first introduced by commit :::::: 55d2375e58a61be072431dd3d3c8a320f4a4a01b KVM: nVMX: Move nested code to dedicated files :::::: TO: Sean Christopherson <sean.j.christopherson(a)intel.com&gt; :::::: CC: Paolo Bonzini <pbonzini(a)redhat.com&gt; --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org -- You received this message because you are subscribed to the Google Groups "Clang Built Linux" group. To unsubscribe from this group and stop receiving emails from it, send an email to clang-built-linux+unsubscribe(a)googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/clang-built-linux/202005162313.CDreQC6s....