On Wed, Aug 17, 2016 at 3:39 PM, Leif Lindholm <leif.lindh...@linaro.org> wrote: > Hi all, > > (Sent to cross-distro with debian-arm on cc.) > > We have an 'interesting' situation ahead of us, or indeed some of us > have already fallen into it: > > ARM64 platforms with > 512GB between the lowest and highest RAM > addresses end up getting their amount of usable memory truncated if > the kernel is built for 39-bit VA (which is what currently happens for > Debian kernels). For 4.7, the arm64 defconfig was changed to enable > 48-bit VA by default. > > While itself not a critical error (but really annoying), in > combination with GRUB putting the initrd near the top of available > RAM, we end up with systems not booting. We think we've also seen > issues with ACPI tables above this waterline. > > Simple - all we need to do then is enable 48-bit VA in the arm64 > kernel config? Well, yes. I know Fedora are already doing this, and I > have raised a bug[1] for Debian to do the same. > > [1] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=834505 > > The problem is - some pieces of software have had time to be written > in a ... let's charitably call it a "focused on amd64" fasion ... with > the embedded assumption that anything above virtual address bit 44 is > a pointer-tag free-for-all. > > On the Debian-ish side, we're coming up on both Ubuntu 16.10 and the > freeze for Stretch, leaving a pretty short window to resolve this > unholy kernel->initrd->userland triangle. > > The applications we know are affected are luajit and mozjs (libv8 is > not a problem). But this has a follow-on cost: both of these are used > by other packages. Other jit/runtime packages could have their own > issues. > > The mozjs bug is fixed on trunk, and will hopefully make it into > release 49[2], but it remains to be seen if that's too late for some > distributions. > > [2] https://bugzilla.mozilla.org/show_bug.cgi?id=1143022 > > For luajit, I'm told this has been fixed on 2.1 branch, but not merged > to master? > > Now, Jeremy (cc:d) tells me the list of currently-known Fedora > packages affected by this are: > couchdb > elinks > erlang-js > freewrl > libEAI > libproxy-mozjs > mediatomb > pacrunner > plowshare > polkit > cinnamon > cjs > cjs > cjs-tests > gjs > gjs > gjs-tests > gnome-shell > 0ad > mongodb > mongodb-server > > Some of these may only need an updated luajit/mozjs package, but some > may need more invasive changes.
Actually that list doesn't include any luajit based packages in Fedora because there's not, upstreamed at least, support for aarch64 in luajit as yet. Peter
