[Bug 1909823] [NEW] RDPMC check on PCE is backwards

[Bruce Merry]

Public bug reported:

At [this
line](https://github.com/qemu/qemu/blob/75ee62ac606bfc9eb59310b9446df3434bf6e8c2/target/i386/tcg/misc_helper.c#L225)
the check on CR4_PCE_MASK is backwards: it's raising an exception if the
flag is set (and CPL != 0) rather than if the flag is clear.

It's low priority at the moment because the instruction isn't
implemented, so you get an illegal opcode exception when expecting a
GPF, or vice versa, but it's a time bomb for if it is ever implemented.

The Intel docs also indicate that CR0.PE influences the protection; I
don't know if that's already reflected in env->hflags & HF_CPL_MASK.

** Affects: qemu
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1909823

Title:
  RDPMC check on PCE is backwards

Status in QEMU:
  New

Bug description:
  At [this
  
line](https://github.com/qemu/qemu/blob/75ee62ac606bfc9eb59310b9446df3434bf6e8c2/target/i386/tcg/misc_helper.c#L225)
  the check on CR4_PCE_MASK is backwards: it's raising an exception if
  the flag is set (and CPL != 0) rather than if the flag is clear.

  It's low priority at the moment because the instruction isn't
  implemented, so you get an illegal opcode exception when expecting a
  GPF, or vice versa, but it's a time bomb for if it is ever
  implemented.

  The Intel docs also indicate that CR0.PE influences the protection; I
  don't know if that's already reflected in env->hflags & HF_CPL_MASK.

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