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Tsirkin" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" It's hardly 6.2 material On Fri, 26 Nov 2021 11:12:55 +0530 (IST) Ani Sinha 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 > > > > 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. > > > > > --- > > > 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 ,id=,bus= > > > > > > > > > +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 > > > > >