Re: [Qemu-devel] [PATCH] virtio: Introduce virtio-testdev

[Anup Patel]

On Tue, Oct 15, 2013 at 2:06 PM, Andrew Jones <address@hidden> wrote:
> On Tue, Oct 15, 2013 at 12:26:10PM +0530, Anup Patel wrote:
>> Hi Andrew,
>>
>> On Mon, Oct 14, 2013 at 9:29 PM, Andrew Jones <address@hidden> wrote:
>> > This is a virtio version of hw/misc/debugexit and should evolve into a
>> > virtio version of pc-testdev. pc-testdev uses the PC's ISA bus, whereas
>> > this testdev can be plugged into a virtio-mmio transport, which is
>> > needed for kvm-unit-tests/arm. virtio-testdev uses the virtio device
>> > config space as a communication channel, and implements an RTAS-like
>> > protocol through it allowing guests to execute commands. Only three
>> > commands are currently implemented;
>> > 1) VERSION: for version compatibility checks
>> > 2) CLEAR:   set all the config space back to zero
>> > 3) EXIT:    exit() from qemu with a status code
>>
>> How about adding RESET command to reset the VM?
>>
>
> Hi Anup,
>
> I'm not opposed to it, but at the moment I'm not sure how we would
> utilize it within kvm-unit-tests. Maybe it would be useful for another
> application though? So maybe we can add it as an add-on patch at the
> time we come up with its use case?

I suggested it because we have "machvirt" machine in QEMU for
KVM ARM/ARM64 which has only VirtIO devices. In "machvirt", we
don't have mechanism to reset the system because none of the
VirtIO devices have such a mechanism. Now since you are introducing
a "testdev", we can have a RESET command in VirtIO and implement
VirtIO REBOOT driver in Linux kernel to use it.

Currently, due to no RESET support in "machvirt" we are not able
to reboot Guest Linux from Guest console.

>
> Thanks for the review!
>
> drew

Thanks,
Anup