Re: [PATCH] docs: Add some details on XenServer PCI devices

["Roger Pau Monné" <roger.pau@citrix.com>]

On Tue, Mar 04, 2025 at 10:21:52AM +0000, Alejandro Vallejo wrote:
> Hi,
> 
> On Fri Feb 28, 2025 at 3:21 PM GMT, Frediano Ziglio wrote:
> > Describe the usage of devices 5853:0002 and 5853:C000.
> >
> > Signed-off-by: Frediano Ziglio <frediano.ziglio@cloud.com>
> > ---
> >  docs/man/xen-pci-device-reservations.7.pod | 9 +++++++++
> >  1 file changed, 9 insertions(+)
> >
> > diff --git a/docs/man/xen-pci-device-reservations.7.pod b/docs/man/xen-pci-device-reservations.7.pod
> > index 9ddf3a18ad..62f3bd2105 100644
> > --- a/docs/man/xen-pci-device-reservations.7.pod
> > +++ b/docs/man/xen-pci-device-reservations.7.pod
> > @@ -10,6 +10,8 @@ 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, presents Xen Platform device with device
> > +ID 0x0002 instead of 0x0001.
> 
> nit: in the interest of future-proofing the doc 's/presents/may present/'?
> 
> >  
> >  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
> > @@ -86,4 +88,11 @@ and unplug protocol.
> >  libxl provides support for creation of a single additional xen-pvdevice.
> >  See the vendor_device parameter in xl.cfg(5).
> >  
> > +=item 2.
> > +
> > +XenServer, for Windows machines, presents a device with ID 0xC000.
> > +This device is a placeholders for Windows update.
> > +Device 0xC000 is presented with a Xen Platform PCI device, usually with ID
> > +0x0002.
> > +
> >  =back
> 
> Wouldn't this be better covered under "=item 1"? Device 0xc000 is a
> xen-pvdevice, so it could be simplified to a single line of "XenServer uses
> device-id=0xc000 for its pvdevice on Windows guests", or something like that.

I think it's important to note that c000 always appears in conjunction
with 0001 or 0002, and it's not a replacement for either of those
devices.

Likewise it's important to note that 0001 and 0002 are to my
understanding mutually exclusive, and only one of those must be
exposed.

Thanks, Roger.