runInLinuxVM, test-driver: use -cpu max instead of -cpu host #95956
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This appears to avoid requiring KVM when it’s not available. This is what I originally though -cpu host did. Unfortunately not much documentation available from the QEMU side on this, but this appears to square with help: $ qemu-system-x86 -cpu help ... x86 host KVM processor with all supported host features x86 max Enables all features supported by the accelerator in the current host ... Whether we actually want to support this not clear, since this only happens when your CPU doesn’t have full KVM support. Some Nix builders are lying about kvm support though. Things aren’t too slow without it though. Fixes NixOS#85394 Alternative to NixOS#83920
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This appears to avoid requiring KVM when it’s not available. This is
what I originally though -cpu host did. Unfortunately not much
documentation available from the QEMU side on this, but this appears
to square with help:
$ qemu-system-x86 -cpu help
...
x86 host KVM processor with all supported host features
x86 max Enables all features supported by the accelerator in the current host
...
Whether we actually want to support this not clear, since this only
happens when your CPU doesn’t have full KVM support. Some Nix builders
are lying about kvm support though. Things aren’t too slow without it
though.
Fixes #85394
Alternative to #83920
/cc @volth @offlinehacker @jpgu-epam