Oh, and cut-and-pasting the same long comment into multiple bug reports is not a good idea, so please don't do that.
-- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1884095 Title: QEMU not sufficiently focused on qEMUlation, with resulting holes in TCG emulation coverage Status in QEMU: Invalid Bug description: 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. NeXTSTEP, Windows, earlier versions of MacOS on ARM Macs. 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. At the very least, there should be a CLEAR distinction which CPUs require KVM to be used, and which can be fully emulated. It should not require wasting an afternoon to figure out that an emulation attempt is futile because TCG lacks essential functionality. To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1884095/+subscriptions
