How many PCI slots can be used per guest?

Solution In Progress - Updated -

Issue

  • Question about the description in the following document.

Virtualization Host Configuration and Guest Installation Guide
Edition 0.4 (RHEL6.3 version)

Chapter 10 describes "KVM Para-virtualized Drivers", and additionally notes as follows.

--- Note --------------------------------------------------------------------
PCI devices are limited by the virtualized system architecture. Out of the 32 PCI devices for a guest, 4 are always defined for a KVM guest, and are not removable. This means there are up to 28 PCI slots available for additional
devices per guest. *Note, however, that only up to 8 devices per guest are supported. Each PCI device in a guest can have up to 8 functions*(1) Each PCI device in a guest can have up to 8 functions
-----------------------------------------------------------------------------

A phrase (1) has been added since RHEL6.3 release. As you know, customers of RHEL6.2 have configured their own system before knowing the phrase. For instance, please guess that a certain customer of RHEL6.2 has created 28 virtio devices with all of 28 available PCI slots prior to RHEL6.3 release.
As far as we see the above note, those 28 devices don't seem to be supported, but we believe they should be. If Red Hat insists they are not supported, we can't make customers understood. Since there should be business impacts on recreating their own XML files, we can't easily ask them to do that. For such customers, we would like you to elaborate the note. We hope such customers don't have to do anything for the note.

Environment

  • Red Hat Enterprise Linux 6.3
  • KVM

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