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df13c0b477
This patch maps /domain/cpu/cache element into -cpu parameters: - <cache mode='passthrough'/> is translated to host-cache-info=on - <cache level='3' mode='emulate'/> is transformed into l3-cache=on - <cache mode='disable'/> is turned in host-cache-info=off,l3-cache=off Any other <cache> element is forbidden. The tricky part is detecting whether QEMU supports the CPU properties. The 'host-cache-info' property is introduced in v2.4.0-1389-ge265e3e480, earlier QEMU releases enabled host-cache-info by default and had no way to disable it. If the property is present, it defaults to 'off' for any QEMU until at least 2.9.0. The 'l3-cache' property was introduced later by v2.7.0-200-g14c985cffa. Earlier versions worked as if l3-cache=off was passed. For any QEMU until at least 2.9.0 l3-cache is 'off' by default. QEMU 2.9.0 was the first release which supports probing both properties by running device-list-properties with typename=host-x86_64-cpu. Older QEMU releases did not support device-list-properties command for CPU devices. Thus we can't really rely on probing them and we can just use query-cpu-model-expansion QMP command as a witness. Because the cache property probing is only reliable for QEMU >= 2.9.0 when both are already supported for quite a few releases, we let QEMU report an error if a specific cache mode is explicitly requested. The other mode (or both if a user requested CPU cache to be disabled) is explicitly turned off for QEMU >= 2.9.0 to avoid any surprises in case the QEMU defaults change. Any older QEMU already turns them off so not doing so explicitly does not make any harm. Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
LibVirt : simple API for virtualization
Libvirt is a C toolkit to interact with the virtualization capabilities
of recent versions of Linux (and other OSes). It is free software
available under the GNU Lesser General Public License. Virtualization of
the Linux Operating System means the ability to run multiple instances of
Operating Systems concurrently on a single hardware system where the basic
resources are driven by a Linux instance. The library aim at providing
long term stable C API initially for the Xen paravirtualization but
should be able to integrate other virtualization mechanisms if needed.
Daniel Veillard <veillard@redhat.com>