On 03/06/2015 04:12, Xiao Guangrong wrote: >> >> Perhaps just use type = MIN(type, curr_type), which also happens to get >> WT vs. WB right? You can also add a >> >> BUILD_BUG_ON(MTRR_TYPE_WRTHROUGH > MTRR_TYPE_WRBACK); >> >> to ensure that the WT vs. WB precedence is correct. > > Only WT and WB are allowed to be overlapped here otherwise is > "undefined behavior". For example if the types are MTRR_TYPE_WRPROT > and MTRR_TYPE_WRTHROUGH, min() will get MTRR_TYPE_WRTHROUGH rather than > "undefined behavior".
Choosing MTRR_TYPE_WRTHROUGH is one example of achieve undefined behavior. Picking one type arbitrarily is just a different kind of undefined behavior. Paolo -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
