1. 11 Sep, 2019 35 commits
  2. 08 Sep, 2019 4 commits
  3. 07 Sep, 2019 1 commit
    • Linus Torvalds's avatar
      Revert "x86/apic: Include the LDR when clearing out APIC registers" · 950b07c1
      Linus Torvalds authored
      This reverts commit 558682b5.
      
      Chris Wilson reports that it breaks his CPU hotplug test scripts.  In
      particular, it breaks offlining and then re-onlining the boot CPU, which
      we treat specially (and the BIOS does too).
      
      The symptoms are that we can offline the CPU, but it then does not come
      back online again:
      
          smpboot: CPU 0 is now offline
          smpboot: Booting Node 0 Processor 0 APIC 0x0
          smpboot: do_boot_cpu failed(-1) to wakeup CPU#0
      
      Thomas says he knows why it's broken (my personal suspicion: our magic
      handling of the "cpu0_logical_apicid" thing), but for 5.3 the right fix
      is to just revert it, since we've never touched the LDR bits before, and
      it's not worth the risk to do anything else at this stage.
      
      [ Hotpluging of the boot CPU is special anyway, and should be off by
        default. See the "BOOTPARAM_HOTPLUG_CPU0" config option and the
        cpu0_hotplug kernel parameter.
      
        In general you should not do it, and it has various known limitations
        (hibernate and suspend require the boot CPU, for example).
      
        But it should work, even if the boot CPU is special and needs careful
        treatment       - Linus ]
      
      Link: https://lore.kernel.org/lkml/156785100521.13300.14461504732265570003@skylake-alporthouse-com/Reported-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
      Acked-by: default avatarThomas Gleixner <tglx@linutronix.de>
      Cc: Bandan Das <bsd@redhat.com>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      950b07c1