# PVPANIC DEVICE

pvpanic device is a simulated device, through which a guest panic event is sent to qemu, and a QMP event is generated. This allows management apps (e.g. libvirt) to be notified and respond to the event.

The management app has the option of waiting for GUEST_PANICKED events, and/or polling for guest-panicked RunState, to learn when the pvpanic device has fired a panic event.

The pvpanic device can be implemented as an ISA device (using IOPORT) or as a PCI device.

## ISA Interface

pvpanic exposes a single I/O port, by default 0x505. On read, the bits recognized by the device are set. Software should ignore bits it doesn’t recognize. On write, the bits not recognized by the device are ignored. Software should set only bits both itself and the device recognize.

### Bit Definition

bit 0

  a guest panic has happened and should be processed by the host

bit 1

  a guest panic has happened and will be handled by the guest; the host should record it or report it, but should not affect the execution of the guest.

bit 2

  a regular guest shutdown has happened and should be processed by the host

## PCI Interface

The PCI interface is similar to the ISA interface except that it uses an MMIO address space provided by its BAR0, 1 byte long. Any machine with a PCI bus can enable a pvpanic device by adding `-device pvpanic-pci` to the command line.

## ACPI Interface

pvpanic device is defined with ACPI ID “QEMU0001”. Custom methods:

### RDPT

To determine whether guest panic notification is supported.

Arguments

  None

Return

  Returns a byte, with the same semantics as the I/O port interface.

### WRPT

To send a guest panic event.

Arguments

  Arg0 is a byte to be written, with the same semantics as the I/O interface.

Return

  None

The ACPI device will automatically refer to the right port in case it is modified.