e59a59a457
Add some documentation about the zpci device and how to use it with pci devices on s390x. Used source: Cornelia Huck's blog post https://people.redhat.com/~cohuck/2018/02/19/notes-on-pci-on-s390x.html Signed-off-by: Sebastian Mitterle <smitterl@redhat.com> Reviewed-by: Cédric Le Goater <clg@redhat.com> Message-Id: <20230127123349.55294-1-smitterl@redhat.com> Reviewed-by: Cornelia Huck <cohuck@redhat.com> Signed-off-by: Thomas Huth <thuth@redhat.com>
42 lines
1.4 KiB
ReStructuredText
42 lines
1.4 KiB
ReStructuredText
PCI devices on s390x
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====================
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PCI devices on s390x work differently than on other architectures and need to
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be configured in a slightly different way.
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Every PCI device is linked with an additional ``zpci`` device.
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While the ``zpci`` device will be autogenerated if not specified, it is
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recommended to specify it explicitly so that you can pass s390-specific
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PCI configuration.
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For example, in order to pass a PCI device ``0000:00:00.0`` through to the
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guest, you would specify::
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qemu-system-s390x ... \
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-device zpci,uid=1,fid=0,target=hostdev0,id=zpci1 \
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-device vfio-pci,host=0000:00:00.0,id=hostdev0
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Here, the zpci device is joined with the PCI device via the ``target`` property.
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Note that we don't set bus, slot or function here for the guest as is common in
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other PCI implementations. Topology information is not available on s390x, and
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the guest will not see any of the bus, slot or function information specified
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on the command line.
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Instead, ``uid`` and ``fid`` determine how the device is presented to the guest
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operating system.
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In case of Linux, ``uid`` will be used in the ``domain`` part of the PCI
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identifier, and ``fid`` identifies the physical slot, i.e.::
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qemu-system-s390x ... \
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-device zpci,uid=7,fid=8,target=hostdev0,id=zpci1 \
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...
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will be presented in the guest as::
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# lspci -v
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0007:00:00.0 ...
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Physical Slot: 00000008
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...
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