mirror of https://github.com/proxmox/mirror_qemu
i386: Resolve CPU models to v1 by default
When using `query-cpu-definitions` using `-machine none`, QEMU is resolving all CPU models to their latest versions. The actual CPU model version being used by another machine type (e.g. `pc-q35-4.0`) might be different. In theory, this was OK because the correct CPU model version is returned when using the correct `-machine` argument. Except that in practice, this breaks libvirt expectations: libvirt always use `-machine none` when checking if a CPU model is runnable, because runnability is not expected to be affected when the machine type is changed. For example, when running on a Haswell host without TSX, Haswell-v4 is runnable, but Haswell-v1 is not. On those hosts, `query-cpu-definitions` says Haswell is runnable if using `-machine none`, but Haswell is actually not runnable using any of the `pc-*` machine types (because they resolve Haswell to Haswell-v1). In other words, we're breaking the "runnability guarantee" we promised to not break for a few releases (see qemu-deprecated.texi). To address this issue, change the default CPU model version to v1 on all machine types, so we make `query-cpu-definitions` output when using `-machine none` match the results when using `pc-*`. This will change in the future (the plan is to always return the latest CPU model version if using `-machine none`), but only after giving libvirt the opportunity to adapt. Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1779078 Signed-off-by: Eduardo Habkost <ehabkost@redhat.com> Message-Id: <20191205223339.764534-1-ehabkost@redhat.com> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>master
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@ -367,6 +367,14 @@ guarantees must resolve the CPU model aliases using te
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``alias-of'' field returned by the ``query-cpu-definitions'' QMP
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``alias-of'' field returned by the ``query-cpu-definitions'' QMP
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command.
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command.
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While those guarantees are kept, the return value of
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``query-cpu-definitions'' will have existing CPU model aliases
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point to a version that doesn't break runnability guarantees
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(specifically, version 1 of those CPU models). In future QEMU
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versions, aliases will point to newer CPU model versions
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depending on the machine type, so management software must
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resolve CPU model aliases before starting a virtual machine.
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@node Recently removed features
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@node Recently removed features
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@appendix Recently removed features
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@appendix Recently removed features
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@ -3981,7 +3981,13 @@ static PropValue tcg_default_props[] = {
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};
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};
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X86CPUVersion default_cpu_version = CPU_VERSION_LATEST;
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/*
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* We resolve CPU model aliases using -v1 when using "-machine
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* none", but this is just for compatibility while libvirt isn't
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* adapted to resolve CPU model versions before creating VMs.
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* See "Runnability guarantee of CPU models" at * qemu-deprecated.texi.
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*/
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X86CPUVersion default_cpu_version = 1;
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void x86_cpu_set_default_version(X86CPUVersion version)
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void x86_cpu_set_default_version(X86CPUVersion version)
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{
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{
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