On Tue, Mar 04, 2025 at 11:17:42AM +0000, Frediano Ziglio wrote: > On Tue, Mar 4, 2025 at 11:08 AM Roger Pau Monné <roger....@citrix.com> wrote: > > > > 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.zig...@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. > > > > Do you have something more precise in mind? Can you suggest what to write?
I'm fine with your proposed text, my reply was to Alejandro to note that I think his proposed text was missing information that was on your original proposal. "XenServer might present a 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." I don't care much whether this is on a separate item or not. My preference would be for adding a second item, as to prevent cluttering the first one. I've also looked at xl.cfg, and it mentions: vendor_device="VENDOR_DEVICE" Selects which variant of the QEMU xen-pvdevice should be used for this guest. Valid values are: none The xen-pvdevice should be omitted. This is the default. xenserver The xenserver variant of the xen-pvdevice (device-id=C000) will be specified, enabling the use of XenServer PV drivers in the guest. Isn't this wrong, as selecting `xenserver` should instead use device-id=0002 but not C000? Maybe I'm not understanding how this is supported to work. > > Likewise it's important to note that 0001 and 0002 are to my > > understanding mutually exclusive, and only one of those must be > > exposed. > > Not exactly sure if this is a must or a should. From my testing, > presenting 2 devices (well, they are mostly the same) works. But, as > they do the same things it seems reasonable to avoid the duplication. > It looks like a good recommendation. I was expecting it to not work, as I imagined Linux would then attempt to initialize the grant tables twice for example. Thanks, Roger.
