[Qemu-devel] [Bug 1349277] Re: AArch64 emulation ignores SPSel=0 when taking (or returning from) an exception at EL1 or greater

[Launchpad Bug Tracker]

This bug was fixed in the package qemu - 2.1+dfsg-7ubuntu3

---------------
qemu (2.1+dfsg-7ubuntu3) vivid; urgency=medium

  * d/p/target-arm-A64-Break-out-aarch64_save-restore_sp.patch
    d/p/target-arm-A64-Respect-SPSEL-in-ERET-SP-restore.patch
    d/p/target-arm-A64-Respect-SPSEL-when-taking-exceptions.patch:
    Cherry-pick of upstream patches in order to fix AArch64 emulation ignoring
    SPSel=0 in certain conditions. (LP: #1349277)
 -- Chris J Arges <address@hidden>   Thu, 04 Dec 2014 14:17:01 -0600

** Changed in: qemu (Ubuntu)
       Status: Fix Committed => Fix Released

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https://bugs.launchpad.net/bugs/1349277

Title:
  AArch64 emulation ignores SPSel=0 when taking (or returning from) an
  exception at EL1 or greater

Status in QEMU:
  Fix Committed
Status in qemu package in Ubuntu:
  Fix Released

Bug description:
  The AArch64 emulation ignores SPSel=0 when:

  (1) taking an interrupt from an exception level greater than EL0
  (e.g., EL1t),

  (2) returning from an exception (via ERET) to an exception level
  greater than EL0 (e.g., EL1t), with SPSR_ELx[SPSel]=0.

  The attached patch fixes the problem in my application.

  Background:

  I'm running a standalone application (toy OS) that is performing
  preemptive multithreading between threads running at EL1t, with
  exception handling / context switching occurring at EL1h.  This bug
  causes the stack pointer to be corrupted in the threads running at
  EL1t (they end up with a version of the EL1h stack pointer (SP_EL1)).

  Occurs in:
        qemu-2.1.0-rc1 (found in)
        commit c60a57ff497667780132a3fcdc1500c83af5d5c0 (current master)

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