Il 09/09/2013 16:11, Arthur Chunqi Li ha scritto: >>> >> +volatile u32 stage; >>> >> +volatile bool init_fail; >> > >> > Why volatile? > Because init_fail is only set but not used later in ept_init(), and if > I don't add volatile, compiler may optimize the setting to init_fail. > > This occasion firstly occurred when I write set_stage/get_stage. If > one variant is set in a function but not used later, the compiler > usually optimizes this setting as redundant assignment and remove it. No, the two are different. "stage" is written several times in the same function, with no code in the middle: stage++; *p = 1; stage++; To the compiler, the first store is dead. The compiler doesn't know that "*p = 1" traps to the hypervisor. But this is not the case for "init_fail". Paolo -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
