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[Qemu-devel] [PATCH RFC 0/1] Extend s390 pci representation in qemu

From: Frank Blaschka
Subject: [Qemu-devel] [PATCH RFC 0/1] Extend s390 pci representation in qemu
Date: Thu, 26 Feb 2015 12:59:47 +0100

For a better understanding of the following patch here is
some general information about how PCI is implemented on the s390
platform. The physical structure of the pci system (bridge, bus, slot)
is not shown to the OS. Instead a firmware and I/O configuration
layer abstracts each PCI card to a bare PCI function.

In essence, the fw layer provides a simple enumeration of the
individual devices, which the s390 pci implementation in the Linux
kernel translates into individual pci domains.

HW layer      |       FW layer       |       Linux kernel
              |                      |
(opaque)      |       function 1     |       0001:00:00.0
              |       function 2     |       0002:00:00.0
              |       function 3     |       0003:00:00.0

In qemu we have following problems:

(1) We have to represent this s390 specific topology information,
    respectively the lack thereof
(2) We have/want to use common qemu PCI infrastructure

The initial implementation did not honor (1) much and tried to derive s390
specific configuration attributes from attributes of qemu pci devices. It
turns out that this is not flexible enough and is not sufficient to support
s390 specific configurations.

The following patch introduces a new zPCI device that kind of represents the
fw layer on real hardware and provides the s390 specific information needed
by guest operating systems. We keep the pci devices the same as in the
general case and just hook them up with the corresponding zPCI device.

Frank Blaschka (1):
  s390x/pci: Extend pci representation by new zpci device

 hw/s390x/s390-pci-bus.c    | 253 ++++++++++++++++++++++++++++++++-------------
 hw/s390x/s390-pci-bus.h    |  38 ++++++-
 hw/s390x/s390-pci-inst.c   |   2 +-
 hw/s390x/s390-virtio-ccw.c |   8 +-
 4 files changed, 227 insertions(+), 74 deletions(-)


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