Re: [Qemu-devel] [PATCH v14 3/4] introduce pvevent device to deal with panicked event

[Alexander Graf]

On 14.03.2013, at 10:43, Paolo Bonzini wrote:

> Il 14/03/2013 10:19, Gleb Natapov ha scritto:
>> On Thu, Mar 14, 2013 at 10:14:12AM +0100, Paolo Bonzini wrote:
>>> Il 14/03/2013 09:15, Hu Tao ha scritto:
>>>> pvevent device is used to send guest panic event from guest to qemu.
>>>> 
>>>> When guest panic happens, pvevent device driver will write a event
>>>> number to IO port 0x505(which is the IO port occupied by pvevent device,
>>>> by default). On receiving the event, pvevent device will pause guest
>>>> cpu(s), and send a qmp event QEVENT_GUEST_PANICKED.  
>>>> 
>>>> TODO: make the IO port configurable
>>> 
>>> The port is already configurable as far as the device is concerned; when
>>> you add the port to the PC boards you will have to wind up fw-cfg.
>> 
>> Why not add fw-cfg when device is created (with -device for instance)?
> 
> It depends on what we decide is the supported interface for the device:
> 
> * it can be an ISA device; the interface is the I/O port and ACPI

Is there any particular reason it's an ISA device with a PIO port, rather than 
a platform / sysbus device with MMIO access? With the latter, we could easily 
reuse the device on other platforms (ppc, arm) and even the guest driver code 
for platforms that do ACPI (arm?).

Also, don't the Xen guys already have a similar interface? Could we at least 
share the guest side implementation maybe?


Alex