Re: [PATCH] Add VirtIO Frame Buffer Support

Avi Kivity
2009-11-03T08:20:56Z

On 11/03/2009 09:50 AM, Alexander Graf wrote:
>
> Ok, imagine this was not this unloved S390 odd architecture but X86.
> The only output choices you have are:
>
> 1) virtio-console
> 2) VNC / SSH over network
> 3) virtio-fb
>
> Now you want to configure a server, probably using yast and all those
> nice graphical utilities, but still enable a firewall so people
> outside don't intrude your machine. Well, you managed to configure the
> firewall by luck to allow VNC, but now you reconfigured it and
> something broke - but VNC was your only chance to access the machine.
> Oops...

x86 has real framebuffers, so software and people expect it. s390
doesn't. How do people manage now?

>>> You also want to see boot messages, have a console login screen,
>>
>> virtio-console does that, except for the penguins. Better, since you
>> can scroll back.
>
> It doesn't do graphics. Ever used yast in text mode?

Once you're in, start ssh+X or vnc. Again, what do people do now?

>
>>> The hardware model isn't exactly new either. It's just the next
>>> logical step to a full PV machine using virtio. If the virtio-fb
>>> stuff turns out to be really fast and reliable, I could even imagine
>>> it being the default target for kvm on ppc as well, as we can't
>>> switch resolutions on the fly there atm.
>>>
>>
>> We could with vmware-vga.
>
> The vmware-port stuff is pretty much tied onto X86. I don't think
> modifying EAX is that easy on PPC ;-).

Yes, though we can probably make it work on ppc with minimal modifications.

>>>> Why? the guest will typically have networking when it's set up, so
>>>> it should have network access during install. You can easily use
>>>> slirp redirection and the built-in dhcp server to set this up with
>>>> relatively few hassles.
>>>
>>> That's how I use it right now. It's no fun.
>>>
>>
>> The toolstack should hide the unfun parts.
>
> You can't hide guest configuration. We as a distribution control the
> kernel. We don't control the user's configuration as that's by design
> the user's choice. The only thing we can do is give users meaningful
> choices to choose from - and having graphics available is definitely
> one of them.

Well, if the user chooses not to have networking then vnc or ssh+x
definitely fail. That would be a strange choice for a server machine.

> Seriously, try to ask someone internally to get access to an S390. I
> think you'll understand my motivations a lot better after having used
> it for a bit.

I actually have a s390 vm (RHEL 4 IIRC). It acts just like any other
remote machine over ssh except that it's especially slow (probably the
host is overloaded). Of course I wouldn't dream of trying to install
something like that though.

--
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