[SeaBIOS] [PATCH] don't expose pvpanic device in the UI

[Michael S. Tsirkin]

On Mon, Aug 05, 2013 at 06:46:06PM +0200, Paolo Bonzini wrote:
> On 08/05/2013 06:18 PM, Michael S. Tsirkin wrote:
> >>>>Depending on the management, "management" could just be the user.
> >>>>Most of the time the user simply says to use virtio in the XML.
> >>>>
> >>>>If it had to be specified manually every time, pvpanic would be
> >>>>just another knob that nobody uses.
> >>>
> >>>Management tools already set XML appropriately depending
> >>>on the guest. If users are happy to leave the device alone,
> >>>we are also happy.
> >>
> >>What if the guest is upgraded?  How does the user know they have
> >>to add a magic device?
> >
> >Device is useless without a driver anyway.
> 
> Who cares?  It doesn't eat valuable resources.  (20 bytes in the
> DSDT are not valuable, a PCI slot is).

IO ports are a bit more valuable.

But I was responding to
what you said "how does the user know they have to add
a magic device" - in the same way that they know
they need a driver.

> >How does user know there's need to install a driver?
> 
> Apparently that was not a problem in Vista and later, when Microsoft
> stopped bugging users with the wizard by default.  And it's never
> been a problem in Linux.
> 
> But they don't need to know that, since probably no one will write a
> driver for pvpanic that runs on Windows XP (6 months before EOL) or
> 2003 (18 months before EOL).
> 
> >So let's add -device pvpanic to QEMU, same as any device, if
> >you think everyone absolutely wants this device explain this
> >to libvirt guys and they'll add it by default, they
> >are much closer to real users and can treat this appropriately.
> 
> It will be exactly the same problem, just thrown further from where
> you can find a real solution---which is not QEMU and is not libvirt,
> it is in the firmware.
> 
> >>Really, all guests handle the missing driver without asking the user.
> >
> >Did you really check them all?
> 
> All those that have a GUI that runs by default, and manage drivers
> in said GUI...

What does GUI have to do with it?
Guests can log errors or fail in a variety of ways.
GUI is not required.


> >>At some point MSFT even issued a hotfix to disable the pesky Found
> >>New Hardware wizard.  Let's treat it as a guest bug, hide the device
> >>altogether with _OSI (detecting Vista or 2008 or Linux),
> >>and declare
> >>that Windows 2000/XP/2003 lack support for pvpanic.
> >
> >Sounds like you merely mean all windows guests.
> 
> ... which means all Windows guests, yes.
> 
> Paolo

Which are the ones where we noticed there's a problem.
But there could be other guests which are problematic.

If you see a mouse in a room, how likely is it that there's
a single mouse there?

This is a PV technology which to me looks like it was
rushed through and not only set on by default, but
without a way to disable it - apparently on the assumption
there's 0 chance it can cause any damage. Now that
we do know the chance it's not there, why not go back
to the standard interface, and why not give
users a chance to enable/disable it?

In other words, let's do the standard thing, and make the new device
available with -device pvpanic.
And in BIOS, let's just obey what QEMU tells us to do,
and not create the device if it's not there.

-- 
MST