[Qemu-devel] [Bug 1838913] Re: Single-step exceptions incorrectly routed to EL1 when ELD is EL2 (TDE = 1) (qemu version 3.1)

[Peter Maydell]

I've just submitted this patchset:
https://patchew.org/QEMU/address@hidden/

which I think should fix this bug. With those changes, the test image
takes a single-step exception to EL2, and then (because there's no code
at the exception entry point) takes a series of EL2-to-EL2 undef
exceptions, which I think is expected and correct behaviour.

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https://bugs.launchpad.net/bugs/1838913

Title:
  Single-step exceptions incorrectly routed to EL1 when ELD is EL2 (TDE
  = 1) (qemu version 3.1)

Status in QEMU:
  In Progress

Bug description:
  Hi,

  I've been encountering issues with QEMU 3.1 when trying to single-step
  EL1 code, with ELD = EL2 (MDCR_EL2.TDE = 1). I could test with latest
  commit in a few hours, if you want.

  EL1 is Aarch64.

  This happens as soon as MDSCR_EL1.SS is set to 1 and ERET is executed:

  - Single-step exceptions are routed to EL1

  Exception return from AArch64 EL2 to AArch64 EL1 PC 0x4000005c
  Taking exception 1 [Undefined Instruction]
  ...from EL1 to EL1
  ...with ESR 0x32/0xca000022
  ...with ELR 0x4000005c
  ...to EL1 PC 0x200 PSTATE 0x3c5

  EC 0x32 (0b110010) is Exception_SoftwareStepLowerEl.

  You can find enclosed minimal code (and resulting .elf) for
  reproduction.

  qemu-system-aarch64 -nographic -machine virt,virtualization=on -d
  unimp,int -cpu cortex-a57 -kernel test_hyp.elf

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