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

[Anup Patel]

On Tue, Oct 15, 2013 at 3:17 PM, Anup Patel <address@hidden> wrote:
> 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.

The RESET support will not fit here only if "testdev" is supposed to be
used for kvm-unit-tests only.

Anyways, its just a suggestion.

>
>>
>> Thanks for the review!
>>
>> drew
>
> Thanks,
> Anup

Regards,
Anup