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?
> ---
> 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
