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docs: Document reserved PCI addresses for QEMU

From time to time we are asked which PCI addresses are reserved
in QEMU. Let's document them in one place, it's easier than
reconstructing the list from the code each time.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Laine Stump <laine@redhat.com>
This commit is contained in:
Michal Privoznik 2020-04-21 16:56:58 +02:00
parent 5eaa9a1cc3
commit c144486479

View File

@ -235,3 +235,53 @@ guest OS rather than as ``0001:08:00.1``, which is the address of the
device on the host. device on the host.
Of course, all the rules and behaviors described above still apply. Of course, all the rules and behaviors described above still apply.
Reserved addresses
==================
Due to some historical reasons hypervisors might expect some PCI
devices to appear at certain addresses instead of 'random' ones.
For QEMU this is machine type and guest architecture dependant.
But to give you at least a gist here is list of reserved PCI
addresses:
For the x86_64 architecture's ``I440FX``-based machine types the following
devices are hard coded into QEMU and can't be moved or eliminated:
============ ======================
0000:00:00.0 Host bridge
0000:00:01.0 ISA bridge
0000:00:01.1 primary IDE controller
0000:00:01.2 PIIX3 USB controller
0000:00:01.3 ACPI (power management) and SMBus controller
============ ======================
The following addresses will be used as default ones for the corresponding
devices (if the address is free or a different address wasn't provided for the
device). It is okay to use this address for any other device.
============ ==================
0000:00:02.0 primary video card
============ ==================
For the x86_64 architecture's ``Q35``-based machine types the following
devices are hard coded into QEMU and can't be moved or eliminated:
============ =======================
0000:00:00.0 Host bridge
0000:00:1f.2 primary SATA controller
0000:00:1f.0 ISA bridge
0000:00:1f.3 SMBus
============ =======================
The following addresses will be used as default ones for the corresponding
devices (if the address is free or a different address wasn't provided for the
device) because that's how real ``Q35`` would do it:
============ ===============
0000:00:1a.0 USB2 controller
0000:00:1b.0 ICH9 sound chip
0000:00:1d.0 USB2 controller
============ ===============