Messages in this thread | | | Date | Mon, 27 Apr 2015 12:29:23 +0200 | From | Michael Mueller <> | Subject | Re: [Qemu-devel] [PATCH v5 15/17] target-s390x: Extend arch specific QMP command query-cpu-definitions |
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On Mon, 27 Apr 2015 10:11:29 +0200 Christian Borntraeger <borntraeger@de.ibm.com> wrote:
> > This patch implements the QMP command 'query-cpu-definitions' in the S390 > > context. The command returns a list of cpu definitions in the current host > > context. A runnable and migratable cpu model has the related attributes > > set to true. The order attribute is used to bring the listed cpu definitions > > in a release order. > > Can you add some explanation why we need the fallback code (e.g. something > along the line, when querying no KVM guest is available and to query the > capabilities we have to open a dummy VM bla bla)
Maybe something like that:
The returned values for attributes like runnable depend on the machine type QEMU is running on. The function kvm_s390_get_machine_props() is used to determine that. If QEMU was started for accelerator KVM, a KVMstate is established and machine properties are retrieved by cpu_model_get(). In case no KVMstate was established, e.g. during QEMU startup in daemonized mode with the default accelerator TCG, a fallback routine named get_machine_props_fallback() is used to retrieve the KVM machine properties. It first creates a temporary VM, performs the required ioctls and finally destroys the VM again.
Michael
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