[Qemu-devel] [Bug 788697] [NEW] [PowerPC] [patch] mtmsr does not preserve high bits of MSR

[Nathan Whitehorn]

Public bug reported:

The mtmsr instruction on 64-bit PPC does not preserve the high-order
32-bits of the MSR the way it is supposed to, instead setting them to 0,
which takes 64-bit code out of 64-bit mode. There is some code that does
the right thing, but it brokenly only preserves these bits when the
thread is not in 64-bit mode (i.e. when it doesn't matter). The attached
patch unconditionally enables this code when TARGET_PPC64 is set, per
the ISA spec, which fixes early boot failures trying to start
FreeBSD/powerpc64 under qemu.

** Affects: qemu
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/788697

Title:
  [PowerPC] [patch] mtmsr does not preserve high bits of MSR

Status in QEMU:
  New

Bug description:
  The mtmsr instruction on 64-bit PPC does not preserve the high-order
  32-bits of the MSR the way it is supposed to, instead setting them to
  0, which takes 64-bit code out of 64-bit mode. There is some code that
  does the right thing, but it brokenly only preserves these bits when
  the thread is not in 64-bit mode (i.e. when it doesn't matter). The
  attached patch unconditionally enables this code when TARGET_PPC64 is
  set, per the ISA spec, which fixes early boot failures trying to start
  FreeBSD/powerpc64 under qemu.