On Tue, May 30, 2017 at 04:14:50AM +0800, kbuild test robot wrote: > 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); > ~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ I definitely thought about this before submitting. size is initialized in the case ctxt->mode < X86EMUL_MODE_PROT64, and ctxt->mode == X86EMUL_MODE_PROT64, but uninitialized in the case ctxt->mode > X86EMUL_MODE_PROT64. Paulo mentions this is impossible in: https://lkml.org/lkml/2017/5/26/62 >>> ctxt->mode is never > X86EMUL_MODE_PROT64 >>> (see the definition of enum x86emul_mode in >>> arch/x86/include/asm/kvm_emulate.h.) >From arch/x86/include/asm/kvm_emulate.h: 272 enum x86emul_mode { 273 X86EMUL_MODE_REAL, /* Real mode. */ 274 X86EMUL_MODE_VM86, /* Virtual 8086 mode. */ 275 X86EMUL_MODE_PROT16, /* 16-bit protected mode. */ 276 X86EMUL_MODE_PROT32, /* 32-bit protected mode. */ 277 X86EMUL_MODE_PROT64, /* 64-bit (long) mode. */ 278 }; I would still rather err on the side of safety, and initialize the variable. So I will submit a v3 initializing size to 0, and check that size was set to a reasonable value at some point before invoke segmented_read_std.
