[Bug 1908781] [NEW] x86-64 not faulting when CS.L = 1 and CS.D = 1

[Bruce Merry]

Public bug reported:

In a UEFI application I accidentally created a code segment descriptor
where both the L and D bits were 1. This is supposed to generate a GP
fault (e.g. see page 2942 of
https://software.intel.com/sites/default/files/managed/39/c5/325462-sdm-
vol-1-2abcd-3abcd.pdf). When running with KVM a fault did indeed occur,
but when not specifying any acceleration, no fault occurred.

Let me know if you need me to develop a minimum example to debug from.
At the moment it's all part of a slightly more complicated bit of code.

Version: 5.2.0 (compiled from source)
Command line options: -smp cores=4 -m 8192 (plus whatever uefi-run adds to plug 
in OVMF and my UEFI application).
Environment: Ubuntu 20.04 on Ryzen 3700X

** Affects: qemu
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1908781

Title:
  x86-64 not faulting when CS.L = 1 and CS.D = 1

Status in QEMU:
  New

Bug description:
  In a UEFI application I accidentally created a code segment descriptor
  where both the L and D bits were 1. This is supposed to generate a GP
  fault (e.g. see page 2942 of
  https://software.intel.com/sites/default/files/managed/39/c5/325462
  -sdm-vol-1-2abcd-3abcd.pdf). When running with KVM a fault did indeed
  occur, but when not specifying any acceleration, no fault occurred.

  Let me know if you need me to develop a minimum example to debug from.
  At the moment it's all part of a slightly more complicated bit of
  code.

  Version: 5.2.0 (compiled from source)
  Command line options: -smp cores=4 -m 8192 (plus whatever uefi-run adds to 
plug in OVMF and my UEFI application).
  Environment: Ubuntu 20.04 on Ryzen 3700X

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