On Sat, Nov 27, 2021 at 1:08 AM Igor Mammedov <imamm...@redhat.com> wrote: > > It's hardly 6.2 material
We introduced the x-hotplug etc property with 6.2. I wanted to make sure that people understand that the x- prefix indicates that this is experimental stuff. We had enough mess with this already. > > On Fri, 26 Nov 2021 11:12:55 +0530 (IST) > Ani Sinha <a...@anisinha.ca> wrote: > > > On Thu, 25 Nov 2021, Michael S. Tsirkin wrote: > > > > > On Thu, Nov 25, 2021 at 05:36:29PM +0530, Ani Sinha wrote: > > > > x-native-hotplug property, when used in order to disable HPC bit on the > > > > PCIE > > > > root ports, can lead to unexpected results from the guest operating > > > > system. > > > > Users are strongly advised not to touch this property in order to > > > > manipulte the > > > > HPC bit. Add a word of caution in the pcie.txt doc file to document > > > > this. > > > > > > > > Signed-off-by: Ani Sinha <a...@anisinha.ca> > > > > > > Do we want to generally document this for all "x-" options? > > > > Yes igor suggested it but I sent this one for two reasons: > > (a) I could not find a place to document this for properties without > > adding a new file. This sounded too bigger a hammer at the present. If you > > can suggest an existing place for documenting this for the property names, > > I will go and add this info there as well. > > > > (b) I think we need to document this experimental property here regardless > > because this doc deals with hotplug and pcie ports and we had too much of > > a mess with this acpi/pci native switch. > > > > When things stabilize a bit, Igor suggested elsewhere that we start a > > separate doc just for hotplug and various options we have and at > > that point we can move this info in this new doc. > > > > https://www.mail-archive.com/libvir-list@redhat.com/msg221746.html > > I'd rather put a blanket statement somewhere, like: > > "x-" prefixed properties are experimental, unstable, internal and > are subject to change/go away without prior notice. > Such properties are not meant for use by users unless explicitly > documented otherwise. I will leave this to someone else to pick it up for the doc side if they are interested. > > > > > > > > --- > > > > docs/pcie.txt | 17 ++++++++++++++++- > > > > 1 file changed, 16 insertions(+), 1 deletion(-) > > > > > > > > diff --git a/docs/pcie.txt b/docs/pcie.txt > > > > index 89e3502075..e1f99f725f 100644 > > > > --- a/docs/pcie.txt > > > > +++ b/docs/pcie.txt > > > > @@ -262,11 +262,26 @@ PCI Express Root Ports (and PCI Express > > > > Downstream Ports). > > > > Port, which may come handy for hot-plugging another device. > > > > > > > > > > > > -5.3 Hot-plug example: > > > > +5.2 Hot-plug example: > > > > Using HMP: (add -monitor stdio to QEMU command line) > > > > device_add <dev>,id=<id>,bus=<PCI Express Root Port Id/PCI Express > > > > Downstream Port Id/PCI-PCI Bridge Id/> > > > > > > > > > > > > +5.3 A word of caution using hotplug on PCI Express Root Ports: > > > > +Starting Qemu version 6.2, PCI Express Root ports have a property > > > > +"x-native-hotplug" ("native-hotplug" for Qemu version 6.1), that can > > > > be used to > > > > +enable or disable hotplug on that port. For example: > > > > + > > > > +-device pcie-root-port,x-native-hotplug=off,... etc. > > > > + > > > > +The "x-" prefix indicates that this property is highly experimental > > > > and can > > > > +lead to unexpected results from the guest operating system if users > > > > try to use > > > > +it to alter the native hotplug on the port. It also means that the > > > > property > > > > +name and its behavior is liable to change in the future and is not > > > > expected to > > > > +be stable across Qemu versions. Therefore, end users are advised not > > > > to change > > > > +the value of this option from its default set value or use it in the > > > > Qemu > > > > +command line. > > > > + > > > > 6. Device assignment > > > > ==================== > > > > Host devices are mostly PCI Express and should be plugged only into > > > > -- > > > > 2.25.1 > > > > > > > > >