=head1 NAME

xen-pci-device-reservations - Xen PCI device ID registry

=head1 Description

PCI vendor ID 0x5853 has been reserved for use by Xen systems in order to
advertise certain virtual hardware to guest virtual machines. The primary
use of this is with device ID 0x0001 to advertise the Xen Platform PCI
device - the presence of this virtual device enables a guest Operating
System (subject to the availability of suitable drivers) to make use of
paravirtualisation features such as disk and network devices etc.
XenServer, for Windows machines, may present Xen Platform device with device
ID 0x0002 instead of 0x0001. Device 0x0001 and 0x0002 should be mutually
exclusive.

Some Xen vendors wish to provide alternative and/or additional guest drivers
that can bind to virtual devices[1]. This may be done using the Xen PCI
vendor ID of 0x5853 and Xen-vendor/device specific PCI device IDs. This file
records reservations made within the device ID range in order to avoid
multiple Xen vendors using conflicting IDs.

=head1 Guidelines

=over 4

=item 1. A vendor may request a range of device IDs by submitting a patch to
         this file.

=item 2. Vendor allocations should be in the range 0xc000-0xfffe to reduce the
         possibility of clashes with community IDs assigned from the bottom up.

=item 3. The vendor is responsible for allocations within the range and should
         try to record specific device IDs in PCI ID databases such as
         https://pci-ids.ucw.cz and https://devicehunt.com

=back

=head1 Reservations

        range     | vendor/product
    --------------+--------------------------------------------------------------
    0x0001        | (Xen Platform PCI device)
    0x0002        | Citrix XenServer (grandfathered allocation for XenServer 6.1)
    0xc000-0xc0ff | Citrix XenServer
    0xc100-0xc1ff | Citrix XenClient
    0xc200-0xc2ff | XCP-ng Project (https://xcp-ng.org)

=head1 Notes

=over 4

=item 1.

Upstream QEMU provides a parameterized device called xen-pvdevice that
can be used to host guest drivers. Execute:

    qemu-system-i386 -device xen-pvdevice,help

for a list of all parameters. The following parameters are relevant to
driver binding:

=over 4

=item  vendor-id (default 0x5853)

The PCI vendor ID and subsystem vendor ID of the device.

=item  device-id (must be specified)

The PCI device ID and subsystem device ID of the device.

=item  revision (default 0x01)

The PCI revision of the device

=back

Also the size parameter (default 0x400000) can be used to specify the
size of the single MMIO BAR that the device exposes. This area may be
used by drivers for mapping grant tables, etc.

Note that the presence of the Xen Platform PCI device is generally a
pre-requisite for an additional xen-pvdevice as it is the platform
device that provides that IO ports necessary for unplugging emulated
devices. See hvm-emulated-unplug.markdown for details of the IO ports
and unplug protocol.

libxl provides support for creation of a single additional xen-pvdevice.
See the vendor_device parameter in xl.cfg(5).

XenServer might present a xen-pvdevice device with ID 0xC000.
Such device is a placeholder for Windows update usage and is always exposed
in conjunction with a Xen Platform PCI device, usually with ID 0x0002

=back
