On Thu, 2019-05-30 at 10:44 +0300, Meelis Roos wrote: > > > The addition of VM_FLUSH_RESET_PERMS for BPF JIT allocations was > > > bisected to prevent boot on an UltraSparc III machine. It was > > > found > > > that > > > sometime shortly after the TLB flush this flag does on vfree of > > > the > > > BPF > > > program, the machine hung. Further investigation showed that > > > before > > > any of > > > the changes for this flag were introduced, with > > > CONFIG_DEBUG_PAGEALLOC > > > configured (which does a similar TLB flush of the vmalloc range > > > on > > > every vfree), this machine also hung shortly after the first > > > vmalloc > > > unmap/free. > > > > > > So the evidence points to there being some existing issue with > > > the > > > vmalloc TLB flushes, but it's still unknown exactly why these > > > hangs > > > are > > > happening on sparc. It is also unknown when someone with this > > > hardware > > > could resolve this, and in the meantime using this flag on it > > > turns a > > > lurking behavior into something that prevents boot. > > > > The sparc TLB flush issue has been bisected and is being worked on > > now, > > so hopefully we won't need this patch: > > https://marc.info/?l=linux-sparc&m=155915694304118&w=2 > > And the sparc64 patch that fixes CONFIG_DEBUG_PAGEALLOC also fixes > booting > of the latest git kernel on Sun V445 where my problem initially > happened. > Thanks Meelis. So the TLB flush on this platform will be fixed and we won't need this patch.
