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--- doc:appunti:linux:sa:virtualization [2019/08/28 11:53] – niccolo
+++ doc:appunti:linux:sa:virtualization [2019/08/28 12:09] (current) – [Libvirt to manage KVM hosts: install, start, stop] niccolo
@@ Line 269: / Line 269: @@
 **NOTICE**: The attributes **arch** and **machine** of tag **%%<os><type>%%** are madatory with **Libvirt 3.0.0** (provided by **Debian 9 Stretch**), they were instead not required in previous versions. To view the the list of supported machines, execute **''qemu-system-x86_64  -machine help''**.
 The VNC port can be assigned automatically (seting it to **''%%port='autoport'%%''**), or assigned statically, e.g. **''%%port='5901'%%''**.
+The **%%<os><type>%%** and **%%<cpu>%%** tags of the XML configuration file, determines what CPU is offered to the guest machine. Here it is the default choosed by ''virt-install'' on a Xeon host (Debian 10 Buster with libvirt 5.0):
+<code xml>
+  <os>
+    <type arch='x86_64' machine='pc'>hvm</type>
+  </os>
+  <cpu mode='host-model' check='partial'>
+    <model fallback='allow'/>
+  </cpu>
+</code>
+See the documentation about **[[https://libvirt.org/formatdomain.html#elementsOS|Operating system booting]]** and **[[https://libvirt.org/formatdomain.html#elementsCPU|CPU model and topology]]** for more info about **%%<os><type>%%** and **%%<cpu>%%** tags.
+You can use a **specific option** if you have an **Intel CPU**:
+<code xml>
+  <cpu mode='custom' match='exact'>
+    <model fallback='allow'>Skylake-Client</model>
+  </cpu>
+</code>
+or this one if you have an **AMD CPU**:
+<code xml>
+  <cpu mode='custom' match='exact'>
+    <model fallback='allow'>Opteron_G3</model>
+  </cpu>
+</code>
 ===== Libvirt and ACPI =====