On Mon, Apr 14, 2014 at 1:15 AM, Markus Armbruster <[email protected]> wrote: > Peter Crosthwaite <[email protected]> writes: > >> Hi Andy, >> >> On Thu, Apr 10, 2014 at 5:55 AM, Andy Lutomirski <[email protected]> wrote: >>> Currently, -M q35 boots linux quite a bit slower than the default >>> machine type. This seems to be because it takes a few hundred ms to >>> determine that there's nothing attached to the AHCI controller. >>> >>> In virtio setups, there will probably never be anything attached to >>> the AHCI controller. Would it be possible to add something like >>> -machine default_storage=off to turn off default storage devices? >>> This could include the AHCI on q35 and the cdrom and such on pc. >>> >>> There's precedent: -machine usb=off turns off the default USB >>> controllers, which is great for setups that use xhci. >>> >> >> Is there a more generic solution to your problem? Can you implement >> command line device removal in a non specific way and avoid having to >> invent AHCI or even "storage" specific arguments. You could >> considering bringing the xhci use case you mentioned under the same >> umbrella. > > USB has always been off by default, at least for the boards I'm familiar > with, due to the USB emulation's non-trivial CPU use. > > There's no such thing as a Q35 board without USB in the physical world. > Can't stop us from making a virtual one, of course. > > Likewise, there's no such thing as a Q35 board without AHCI in the > physical world, and again that can't stop us from making a virtual one. > > The difference to USB is that our q35 machines have always had AHCI even > with -nodefaults. You seem to propose adding a switch to disable AHCI, > yet leave it enabled with -nodefaults. > > -nodefaults should give you a board with all the optional components > suppressed.
Will this break libvirt, which may expect -nodefaults to still come with an IDE bus? > > On the one hand, I'd rather not add exceptions to -nodefaults "give me > the board with all its optional components suppressed" semantics. > > On the other hand, a few hundred ms are a long time. That's why I proposed a new option. Yes, it's ugly :/ --Andy
