On Wed, Mar 28, 2018 at 3:49 AM, Ken Moffat <zarniwh...@ntlworld.com> wrote: > Thought I'd mention this here, because with current gcc the use (or > omission!) of -march in CFLAGS isn't doing what I had expected. > > Background: my buildscripts are on nfs, as are my sources, so in the > past I've found it convenient to bring up a new machine by building > what I hope will be a suitable LFS on an existing system, fixing up > the kernel, and then copying it over - usually followed by sorting > out changes to video drivers / kernel config / hardware monitoring. > > The new box is my first Ryzen (nothing fancy, just an R3 1300X for > four real cores with good cache sizes), and I was hoping to use the > initial system to get to grips with whatever I may, or may not, need > to do to get nouveau running. Recently I've been using > -march=native in my CFLAGS (in the hope that compilation might be > less slow), but for this build I dropped that and made sure that gmp > used config.fsf. > > It booted fine on the build machine (a Kaveri, model 15h), but when > I copied it over and tried to chroot from SystemRescueCD I got > 'illegal instruction'. Eventually I dug out an OpenSuse disk and > tried that in recovery mode: same result, but it told me the problem > was in ld-2.27.so. > > Googling around, I came upon old gentoo threads where -march=k8 was > recommended because Ryzens omit 4 instructions which were available > on Excavator CPUs. Return to start, do not pass go, do not collect > 200 currency-units. So, I tried that. But the same result. That is > what really concerns me. > > Then I got lucky - saved the kernel, modules, .config and tried > loading a backup from a different machine (an AMD Phenom - much > earlier x86_64, I think that is fam 10h) - with that I could chroot > from SystemRescueCD. Installed grub, fixed things up, booted. But > that wasn't a minimal system, so I've deferred looking at whatever > nouveau may, or may not, need for Xorg on this hardware (it's only a > GT710 - the bottom of the range, no fan and a vga output). It is now > getting towards the end of chapter 6 in a native build. > > I'm really mentioning this in case anybody else gets a Ryzen and > tries the same approach.
For Rysen i use these flags: -march=x86-64 -mtune=generic -mno-fma4 -mno-tbm -mno-xop -mno-lwp The no-fma4 etc are flags for instruntions that rysen does not have. -- http://lists.linuxfromscratch.org/listinfo/lfs-support FAQ: http://www.linuxfromscratch.org/blfs/faq.html Unsubscribe: See the above information page Do not top post on this list. A: Because it messes up the order in which people normally read text. Q: Why is top-posting such a bad thing? A: Top-posting. Q: What is the most annoying thing in e-mail? http://en.wikipedia.org/wiki/Posting_style
