[Bug 1877781] [NEW] TCG does not support x2APIC emulation

[Bug 1877781] [NEW] TCG does not support x2APIC emulation

[Dan Cross]

Public bug reported:

This is not a bug so much as a feature request.

It would be great if there was a pure-software emulation of the x2APIC
on x86_64, so that it could be used on systems that don't support such
providing a thing on via a host-based solution (e.g., KVM etc). KVM
provides this, but that doesn't help if you're working on a machine that
doesn't support KVM.

** Affects: qemu
     Importance: Undecided
         Status: New

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Title:
  TCG does not support x2APIC emulation

Status in QEMU:
  New

Bug description:
  This is not a bug so much as a feature request.

  It would be great if there was a pure-software emulation of the x2APIC
  on x86_64, so that it could be used on systems that don't support such
  providing a thing on via a host-based solution (e.g., KVM etc). KVM
  provides this, but that doesn't help if you're working on a machine
  that doesn't support KVM.

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[Bug 1877781] Re: TCG does not support x2APIC emulation

[Ronald Antony]

If I may be so free:

It seems that QEMU has stopped emphasizing the EMU part of the name, and
is too much focused on virtualization.

My interest is at running legacy operating systems, and as such, they must run on foreign CPU platforms. m68 on intel, intel on ARM, etc.
Time doesn't stand still, and reliance on KVM and similar x86-on-x86 tricks, which allow the delegation of certain CPU features to the host CPU is going to not work going forward.

If the rumored transition of Apple to ARM is going to take place, people
will want to e.g. emulate for testing or legacy purposes a variety of
operating systems, incl. earlier versions of MacOS.

Testing that scenario, i.e. macOS on an ARM board with the lowest
possible CPU capable of running modern macOS, results in these problems
(and of course utter failure achieving the goal):

qemu-system-x86_64: warning: TCG doesn't support requested feature: CPUID.01H:ECX.fma [bit 12]
qemu-system-x86_64: warning: TCG doesn't support requested feature: CPUID.01H:ECX.avx [bit 28]
qemu-system-x86_64: warning: TCG doesn't support requested feature: CPUID.07H:EBX.avx2 [bit 5]
qemu-system-x86_64: warning: TCG doesn't support requested feature: CPUID.80000007H:EDX.invtsc [bit 8]
qemu-system-x86_64: warning: TCG doesn't support requested feature: CPUID.0DH:EAX.xsavec [bit 1]

And this is emulating a lowly Penryn CPU with the required CPU flags for macOS:
-cpu Penryn,vendor=GenuineIntel,+sse3,+sse4.2,+aes,+xsave,+avx,+xsaveopt,+xsavec,+xgetbv1,+avx2,+bmi2,+smep,+bmi1,+fma,+movbe,+invtsc

Attempting to emulate a more feature laden intel CPU results in even
more issues.

I would propose that no CPU should be considered supported unless it can
be fully handled by TCG on a non-native host. KVM, native-on-native etc.
are nice to have, but peripheral to qEMUlation when it boils down to it.

-- 
You received this bug notification because you are a member of qemu-
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https://bugs.launchpad.net/bugs/1877781

Title:
  TCG does not support x2APIC emulation

Status in QEMU:
  New

Bug description:
  This is not a bug so much as a feature request.

  It would be great if there was a pure-software emulation of the x2APIC
  on x86_64, so that it could be used on systems that don't support such
  providing a thing on via a host-based solution (e.g., KVM etc). KVM
  provides this, but that doesn't help if you're working on a machine
  that doesn't support KVM.

To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1877781/+subscriptions

[Bug 1877781] Re: TCG does not support x2APIC emulation

[Thomas Huth]

The QEMU project is currently moving its bug tracking to another system.
For this we need to know which bugs are still valid and which could be
closed already. Thus we are setting older bugs to "Incomplete" now.

If the bug has already been fixed in the latest upstream version of QEMU,
then please close this ticket as "Fix released".

If it is not fixed yet and you think that this bug report here is still
valid, then you have two options:

1) If you already have an account on gitlab.com, please open a new ticket
for this problem in our new tracker here:

    https://gitlab.com/qemu-project/qemu/-/issues

and then close this ticket here on Launchpad (or let it expire auto-
matically after 60 days). Please mention the URL of this bug ticket on
Launchpad in the new ticket on GitLab.

2) If you don't have an account on gitlab.com and don't intend to get
one, but still would like to keep this ticket opened, then please switch
the state back to "New" within the next 60 days (otherwise it will get
closed as "Expired"). We will then eventually migrate the ticket auto-
matically to the new system.

Thank you and sorry for the inconvenience.


** Changed in: qemu
       Status: New => Incomplete

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https://bugs.launchpad.net/bugs/1877781

Title:
  TCG does not support x2APIC emulation

Status in QEMU:
  Incomplete

Bug description:
  This is not a bug so much as a feature request.

  It would be great if there was a pure-software emulation of the x2APIC
  on x86_64, so that it could be used on systems that don't support such
  providing a thing on via a host-based solution (e.g., KVM etc). KVM
  provides this, but that doesn't help if you're working on a machine
  that doesn't support KVM.

To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1877781/+subscriptions

[Bug 1877781] Re: TCG does not support x2APIC emulation

[Thomas Huth]

This ticket has been moved here (thanks, Dan!):
https://gitlab.com/qemu-project/qemu/-/issues/330
... so I'm closing this on Launchpad now.

** Bug watch added: gitlab.com/qemu-project/qemu/-/issues #330
   https://gitlab.com/qemu-project/qemu/-/issues/330

** Changed in: qemu
       Status: Incomplete => Invalid

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https://bugs.launchpad.net/bugs/1877781

Title:
  TCG does not support x2APIC emulation

Status in QEMU:
  Invalid

Bug description:
  This is not a bug so much as a feature request.

  It would be great if there was a pure-software emulation of the x2APIC
  on x86_64, so that it could be used on systems that don't support such
  providing a thing on via a host-based solution (e.g., KVM etc). KVM
  provides this, but that doesn't help if you're working on a machine
  that doesn't support KVM.

To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1877781/+subscriptions