@@ -490,7 +490,7 @@ S: Supported
F: include/sysemu/kvm_xen.h
F: target/i386/kvm/xen*
F: hw/i386/kvm/xen*
-F: tests/avocado/xen_guest.py
+F: tests/avocado/kvm_xen_guest.py
Guest CPU Cores (other accelerators)
------------------------------------
@@ -15,46 +15,24 @@ Setup
-----
Xen mode is enabled by setting the ``xen-version`` property of the KVM
-accelerator, for example for Xen 4.10:
+accelerator, for example for Xen 4.17:
.. parsed-literal::
- |qemu_system| --accel kvm,xen-version=0x4000a,kernel-irqchip=split
+ |qemu_system| --accel kvm,xen-version=0x40011,kernel-irqchip=split
Additionally, virtual APIC support can be advertised to the guest through the
``xen-vapic`` CPU flag:
.. parsed-literal::
- |qemu_system| --accel kvm,xen-version=0x4000a,kernel-irqchip=split --cpu host,+xen_vapic
+ |qemu_system| --accel kvm,xen-version=0x40011,kernel-irqchip=split --cpu host,+xen-vapic
When Xen support is enabled, QEMU changes hypervisor identification (CPUID
0x40000000..0x4000000A) to Xen. The KVM identification and features are not
advertised to a Xen guest. If Hyper-V is also enabled, the Xen identification
moves to leaves 0x40000100..0x4000010A.
-The Xen platform device is enabled automatically for a Xen guest. This allows
-a guest to unplug all emulated devices, in order to use Xen PV block and network
-drivers instead. Under Xen, the boot disk is typically available both via IDE
-emulation, and as a PV block device. Guest bootloaders typically use IDE to load
-the guest kernel, which then unplugs the IDE and continues with the Xen PV block
-device.
-
-This configuration can be achieved as follows
-
-.. parsed-literal::
-
- |qemu_system| -M pc --accel kvm,xen-version=0x4000a,kernel-irqchip=split \\
- -drive file=${GUEST_IMAGE},if=none,id=disk,file.locking=off -device xen-disk,drive=disk,vdev=xvda \\
- -drive file=${GUEST_IMAGE},index=2,media=disk,file.locking=off,if=ide
-
-It is necessary to use the pc machine type, as the q35 machine uses AHCI instead
-of legacy IDE, and AHCI disks are not unplugged through the Xen PV unplug
-mechanism.
-
-VirtIO devices can also be used; Linux guests may need to be dissuaded from
-umplugging them by adding 'xen_emul_unplug=never' on their command line.
-
Properties
----------
@@ -63,7 +41,10 @@ The following properties exist on the KVM accelerator object:
``xen-version``
This property contains the Xen version in ``XENVER_version`` form, with the
major version in the top 16 bits and the minor version in the low 16 bits.
- Setting this property enables the Xen guest support.
+ Setting this property enables the Xen guest support. If Xen version 4.5 or
+ greater is specified, the HVM leaf in Xen CPUID is populated. Xen version
+ 4.6 enables the vCPU ID in CPUID, and version 4.17 advertises vCPU upcall
+ vector support to the guest.
``xen-evtchn-max-pirq``
Xen PIRQs represent an emulated physical interrupt, either GSI or MSI, which
@@ -83,8 +64,78 @@ The following properties exist on the KVM accelerator object:
through simultaneous grants. For guests with large numbers of PV devices and
high throughput, it may be desirable to increase this value.
-OS requirements
----------------
+Xen paravirtual devices
+-----------------------
+
+The Xen PCI platform device is enabled automatically for a Xen guest. This
+allows a guest to unplug all emulated devices, in order to use paravirtual
+block and network drivers instead.
+
+Those paravirtual Xen block, network (and console) devices can be created
+through the command line, and/or hot-plugged.
+
+To provide a Xen console device, define a character device and then a device
+of type ``xen-console`` to connect to it. For the Xen console equivalent of
+the handy ``-serial mon:stdio`` option, for example:
+
+.. parsed-literal::
+ -chardev stdio,mux=on,id=char0,signal=off -mon char0 \\
+ -device xen-console,chardev=char0
+
+The Xen network device is ``xen-net-device``, which becomes the default NIC
+model for emulated Xen guests, meaning that just the default NIC provided
+by QEMU should automatically work and present a Xen network device to the
+guest.
+
+Disks can be configured with '``-drive file=${GUEST_IMAGE},if=xen``' and will
+appear to the guest as ``xvda`` onwards.
+
+Under Xen, the boot disk is typically available both via IDE emulation, and
+as a PV block device. Guest bootloaders typically use IDE to load the guest
+kernel, which then unplugs the IDE and continues with the Xen PV block device.
+
+This configuration can be achieved as follows:
+
+.. parsed-literal::
+
+ |qemu_system| --accel kvm,xen-version=0x40011,kernel-irqchip=split \\
+ -drive file=${GUEST_IMAGE},if=xen \\
+ -drive file=${GUEST_IMAGE},file.locking=off,if=ide
+
+VirtIO devices can also be used; Linux guests may need to be dissuaded from
+umplugging them by adding '``xen_emul_unplug=never``' on their command line.
+
+Booting Xen PV guests
+---------------------
+
+Booting PV guest kernels is possible by using the Xen PV shim (a version of Xen
+itself, designed to run inside a Xen HVM guest and provide memory management
+services for one guest alone).
+
+The Xen binary is provided as the ``-kernel`` and the guest kernel itself (or
+PV Grub image) as the ``-initrd`` image, which actually just means the first
+multiboot "module". For example:
+
+.. parsed-literal::
+
+ |qemu_system| --accel kvm,xen-version=0x40011,kernel-irqchip=split \\
+ -chardev stdio,id=char0 -device xen-console,chardev=char0 \\
+ -display none -m 1G -kernel xen -initrd bzImage \\
+ -append "pv-shim console=xen,pv -- console=hvc0 root=/dev/xvda1" \\
+ -drive file=${GUEST_IMAGE},if=xen
+
+The Xen image must be built with the ``CONFIG_XEN_GUEST`` and ``CONFIG_PV_SHIM``
+options, and as of Xen 4.17, Xen's PV shim mode does not support using a serial
+port; it must have a Xen console or it will panic.
+
+The example above provides the guest kernel command line after a separator
+(" ``--`` ") on the Xen command line, and does not provide the guest kernel
+with an actual initramfs, which would need to listed as a second multiboot
+module. For more complicated alternatives, see the command line
+documentation for the ``-initrd`` option.
+
+Host OS requirements
+--------------------
The minimal Xen support in the KVM accelerator requires the host to be running
Linux v5.12 or newer. Later versions add optimisations: Linux v5.17 added
@@ -3986,14 +3986,22 @@ ERST
DEF("initrd", HAS_ARG, QEMU_OPTION_initrd, \
"-initrd file use 'file' as initial ram disk\n", QEMU_ARCH_ALL)
SRST
+
``-initrd file``
Use file as initial ram disk.
``-initrd "file1 arg=foo,file2"``
This syntax is only available with multiboot.
- Use file1 and file2 as modules and pass arg=foo as parameter to the
- first module.
+ Use file1 and file2 as modules and pass ``arg=foo`` as parameter to the
+ first module. Commas can be provided in module parameters by doubling
+ them on the command line to escape them:
+
+``-initrd "bzImage earlyprintk=xen,,keep root=/dev/xvda1,initrd.img"``
+ Multiboot only. Use bzImage as the first module with
+ "``earlyprintk=xen,keep root=/dev/xvda1``" as its command line,
+ and initrd.img as the second module.
+
ERST
DEF("dtb", HAS_ARG, QEMU_OPTION_dtb, \