Hi Nick, [auto build test WARNING on kvm/linux-next] [also build test WARNING on v4.12-rc3 next-20170529] [if your patch is applied to the wrong git tree, please drop us a note to help improve the system] url: https://github.com/0day-ci/linux/commits/Nick-Desaulniers/KVM-x86-avoid-large-stack-allocations-in-em_fxrstor/20170530-040058 base: https://git.kernel.org/pub/scm/virt/kvm/kvm.git linux-next config: x86_64-allmodconfig (attached as .config) compiler: gcc-6 (Debian 6.2.0-3) 6.2.0 20160901 reproduce: # save the attached .config to linux build tree make ARCH=x86_64 Note: it may well be a FALSE warning. FWIW you are at least aware of it now. http://gcc.gnu.org/wiki/Better_Uninitialized_Warnings All warnings (new ones prefixed by >>): arch/x86/kvm/emulate.c: In function 'em_fxrstor': >> arch/x86/kvm/emulate.c:4015:5: warning: 'size' may be used uninitialized in this function [-Wmaybe-uninitialized] rc = segmented_read_std(ctxt, ctxt->memop.addr.mem, &fx_state, size); ~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ vim +/size +4015 arch/x86/kvm/emulate.c 3999 4000 if (ctxt->mode < X86EMUL_MODE_PROT64) { 4001 rc = asm_safe("fxsave %[fx]", , [fx] "+m"(fx_state)); 4002 if (rc != X86EMUL_CONTINUE) 4003 return rc; 4004 /* 4005 * Hardware doesn't save and restore XMM 0-7 without 4006 * CR4.OSFXSR, but does save and restore MXCSR. 4007 */ 4008 if (ctxt->ops->get_cr(ctxt, 4) & X86_CR4_OSFXSR) 4009 size = offsetof(struct fxregs_state, xmm_space[8]); 4010 else 4011 size = offsetof(struct fxregs_state, xmm_space[0]); 4012 } else if (ctxt->mode == X86EMUL_MODE_PROT64) 4013 size = offsetof(struct fxregs_state, xmm_space[16]); 4014 > 4015 rc = segmented_read_std(ctxt, ctxt->memop.addr.mem, &fx_state, size); 4016 if (rc != X86EMUL_CONTINUE) 4017 return rc; 4018 4019 if (fx_state.mxcsr >> 16) 4020 return emulate_gp(ctxt, 0); 4021 4022 if (rc == X86EMUL_CONTINUE) 4023 rc = asm_safe("fxrstor %[fx]", : [fx] "m"(fx_state)); --- 0-DAY kernel test infrastructure Open Source Technology Center https://lists.01.org/pipermail/kbuild-all Intel Corporation
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