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.
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.