[Qemu-devel] [Bug 796202] Re: Doing a 64 bit load from a 32 bit local APIC register is allowed

[Launchpad Bug Tracker]

[Expired for QEMU because there has been no activity for 60 days.]

** Changed in: qemu
       Status: Incomplete => Expired

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https://bugs.launchpad.net/bugs/796202

Title:
  Doing a 64 bit load from a 32 bit local APIC register is allowed

Status in QEMU:
  Expired

Bug description:
  Doing

  u64 lapic_idregister = (u64) fix_to_virt(FIX_APIC_BASE) + 0x20;

  and later in an interrupt handler

  movq (lapic_idregister), %rcx
  movq (%rcx), %rcx

  in a linux kernel module works in qemu 0.13.91 but not on real hardware (it 
simply reboots).
  On real hardware only

  movl (%rcx), %ecx

  works (also in qemu).

  Commandline:
  qemu-system-x86_64 \
                -kernel $LINUXDIR/arch/x86_64/boot/bzImage \
                -hda $BUILDROOTDIR/output/images/rootfs.ext2 \
                -append "root=/dev/sda rw rootfstype=ext2 maxcpus=4" \
                -cpu phenom \
                -smp 4 \
                -gdb tcp::1234 \
                -net nic -net user

  Guest:
  Vanilla Linux Kernel 2.6.37.6 64-bit with buildroot

  Mikael Pettersson from the linux kernel mailinglist told me it's an
  accepts-invalid bug in qemu.

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