On Sat, May 16, 2020 at 8:39 AM kbuild test robot <lkp@xxxxxxxxx> wrote: > > 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@xxxxxxxxx> > > 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; ^ definition of 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; ^ assignment > 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; ^ assignment > 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) ^ use While the BUG_ON in the default case should prevent the problematic use, Clang can't understand the semantics of BUG_ON. roots_to_free should just be initialized to zero. > 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@xxxxxxxxx> > :::::: CC: Paolo Bonzini <pbonzini@xxxxxxxxxx> > > --- > 0-DAY CI Kernel Test Service, Intel Corporation > https://lists.01.org/hyperkitty/list/kbuild-all@xxxxxxxxxxxx > > -- > 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@xxxxxxxxxxxxxxxx. > To view this discussion on the web visit https://groups.google.com/d/msgid/clang-built-linux/202005162313.CDreQC6s%25lkp%40intel.com. -- Thanks, ~Nick Desaulniers
