On Tue, Aug 06, 2013 at 12:20:27PM +0300, Gleb Natapov wrote:
On Tue, Aug 06, 2013 at 10:45:01AM +0200, Andreas Färber wrote:
Am 06.08.2013 10:36, schrieb Gleb Natapov:
On Tue, Aug 06, 2013 at 11:33:10AM +0300, Michael S. Tsirkin wrote:
On Tue, Aug 06, 2013 at 10:21:52AM +0300, Gleb Natapov wrote:
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?
You should be able to disable it with: -device pvpanic,ioport=0
Doesn't work for me.
Bug that should be fixed. With this command line _STA should return zero.
Besides, both -device pvpanic and use of ioport=0 to disable it are completely undocumented.
Not the only undocumented thing in QEMU command line :)
I disagree: -device adds a device, not removes one. It will still be present.
I assume you are answering to the quote about ioport=0, not documentation here. ioport=0 does not removes the device, it disables it. The claim was it cannot be disabled, it can (assuming no bugs), but it should not be.
I am neutral as to whether qemu-system-x86_64 should have it enabled by default or not. But if we want to suppress it, then -nodefaults should disable it. Since libvirt uses that though, it would mean libvirt would need to add it back, whether via user's XML domain config or by libvirt itself based on some version/etc. heuristics.
There is no clear definition of what -nodefaults should or should not do. Should it disable PV ACPI hotplug device? Should it create a machine with no mmio/io regions registered at all?
We can't change the meaning for existing devices. So we need to keep everything that it historically included. But it's a good question whether e.g. ACPI hotplug for q35 should be a separate device, and disabled with -nodefaults.
pvpanic presents itself as a separate device, this is different from PV ACPI hotplug which is part of PIIX.