[PATCH docs 2/3] qm: add document section for the pvpanic device

[Kaiyang Wu <wukaiyang2003@gmail.com>]

Document the variants of the pvpanic device, and corresponding driver
requirements on different virtual machine operating systems.

Signed-off-by: Kaiyang Wu <wukaiyang@loongfans.cn>
---
 qm.adoc | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/qm.adoc b/qm.adoc
index 5b46cdc..afa7d32 100644
--- a/qm.adoc
+++ b/qm.adoc
@@ -1472,6 +1472,35 @@ tag (name used to mount the device on the guest).
 For more information on available virtiofsd parameters, see the
 https://gitlab.com/virtio-fs/virtiofsd[GitLab virtiofsd project page].
 
+[[qm_pvpanic]]
+Pvpanic
+~~~~~~~
+
+Pvpanic is a device to send system panic events to QEMU. It allows to
+provide extra VM status when the VM system crashes.
+
+To add a pvpanic device run the following command:
+
+----
+qm set <vmid> -pvpanic0 <type>
+----
+
+Supported pvpanic device types are:
+
+* `pvpanic`: pvpanic ISA device
+* `pvpanic-pci`: pvpanic PCI device
+
+Linux VMs with kernel >=3.1 support pvpanic ISA device
+(https://www.kernelconfig.io/CONFIG_PVPANIC[pvpanic ISA driver]), and with
+kernel >=5.2 support pvpanic PCI device
+(https://www.kernelconfig.io/CONFIG_PVPANIC_PCI[pvpanic PCI driver]).
+
+Windows VMs require
+https://github.com/virtio-win/kvm-guest-drivers-windows/[kvm-guest-drivers-windows]
+to use pvpanic.
+
+FreeBSD VMs do not support pvpanic.
+
 [[qm_bootorder]]
 Device Boot Order
 ~~~~~~~~~~~~~~~~~
-- 
2.55.0