Il 31/10/2013 15:34, Gleb Natapov ha scritto: > I haven't checked AMD doc, but if it is documented that lahf/sahf #UDs at 64 > bit we should emulate it correctly. It says "The LAHF instruction can only be executed in 64-bit mode if supported by the processor implementation. Check the status of ECX bit 0 returned by CPUID function 8000_0001h to verify that the processor supports LAHF in 64-bit mode". Same as Intel---in fact 80000001h is an "AMD leaf" so to speak. I found "AMD introduced support for the instructions with their Athlon 64, Opteron and Turion 64 revision D processors in March 2005 and Intel introduced support for the instructions with the Pentium 4 G1 stepping in December 2005". I think we can for all practical purposes ignore the lahf_lm CPUID flag. > Who knows what code depends on it. > Of course I pretty much doubt we will ever emulate sahf in 64 bit mode Yep. Paolo -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html