Sorry about the time travel.
I will try to give up that super power... :(
On 4/14/20 11:06 PM, Boris Fiuczynski wrote:
On 4/15/20 12:51 PM, Cornelia Huck wrote:
Add some information on how pci address work on s390x.
Signed-off-by: Cornelia Huck <cohuck@xxxxxxxxxx>
Conny, thanks for catching this "wacky case"... :)
I took the liberty to remove "completely" because there needs to be room
for pci multifunction support... :D
---
docs/pci-addresses.rst | 63 ++++++++++++++++++++++++++++++++++++++++++
1 file changed, 63 insertions(+)
diff --git a/docs/pci-addresses.rst b/docs/pci-addresses.rst
index 923783a151b0..9e241a24fcfb 100644
--- a/docs/pci-addresses.rst
+++ b/docs/pci-addresses.rst
@@ -184,3 +184,66 @@ guest OS rather than as ``0001:08:00.1``, which
is the address of the
device on the host.
Of course, all the rules and behaviors described above still apply.
+
+zPCI addresses
+==============
+
+For s390x machines, PCI addresses are handled yet differently. No
+topology information is relayed in the PCI addresses; instead, the
+``fid`` and ``uid`` elements of the ``zpci`` device convey information.
Should it be mentioned that qemu uses the pci address internally to plug
the device into its pci bus since the pci address as far as I know must
still be properly provided or generated.
+In the simplest case, the following XML snippet
+
+::
+
+ <controller type='pci' index='0' model='pci-root'/>
+ <controller type='pci' index='1' model='pci-bridge'>
+ <model name='pci-bridge'/>
+ <target chassisNr='1'/>
+ <address type='pci' domain='0x0000' bus='0x00' slot='0x01'
function='0x0'>
+ <zpci uid='0x0002' fid='0x00000001'/>
+ </address>
+ </controller>
+ <interface type='bridge'>
+ <mac address='02:ca:fe:fa:ce:04'/>
+ <source bridge='virbr0'/>
+ <model type='virtio'/>
+ <address type='pci' domain='0x0000' bus='0x01' slot='0x01'
function='0x0'>
+ <zpci uid='0x0001' fid='0x00000000'/>
+ </address>
+ </interface>
+
+will result in the following in a Linux guest::
+
+ 0001:00:00.0 Ethernet controller: Red Hat, Inc. Virtio network device
+
+Note that the PCI bridge is not visible in the guest; s390x always
has a flat
+topology.
+
+Neither are any changes in the PCI address visible in the guest;
replacing
+the PCI address for the virtio-net device with
+
+::
+
+ <address type='pci' domain='0x0000' bus='0x01' slot='0x07'
function='0x3'>
+
+will result in the exactly same view in the guest, as the addresses
there
+are generated from the information provided via the ``zpci`` element (in
+fact, from the ``uid``).
+
This explains that the uid is used by the guest to define the pci domain
of the guest device.
How about an addition for the fid? Something like:
The function id 'fid' defines the slot address of the pci card in the
guest. It can be observed in the guest at /sys/bus/pci/slots. In the
example given above the card would be at /sys/bus/pci/slots/00000000.
+Therefore, replacing the virtio-net device definition with the
following XML
+snippet
+
+::
+
+ <interface type='bridge'>
+ <mac address='02:ca:fe:fa:ce:04'/>
+ <source bridge='virbr0'/>
+ <model type='virtio'/>
+ <address type='pci' domain='0x0000' bus='0x01' slot='0x07'
function='0x3'>
+ <zpci uid='0x0007' fid='0x00000003'/>
+ </address>
+ </interface>
+
+will yield the following result in a Linux guest::
+
+ 0007:00:00.0 Ethernet controller: Red Hat, Inc. Virtio network device
and the card would be at /sys/bus/pci/slots/00000003.
--
Mit freundlichen Grüßen/Kind regards
Boris Fiuczynski
IBM Deutschland Research & Development GmbH
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