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[PATCH-for-6.2] docs: add a word of caution on x-native-hotplug property

From: Ani Sinha
Subject: [PATCH-for-6.2] docs: add a word of caution on x-native-hotplug property for pcie-root-ports
Date: Thu, 25 Nov 2021 17:36:29 +0530

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 <ani@anisinha.ca>
 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

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