On Fri, Jul 15, 2022 at 02:36:36PM +0800, Han Han wrote:
> On Wed, Jul 13, 2022 at 7:04 PM Daniel P. Berrangé
> wrote:
>
> > On Wed, Jul 13, 2022 at 07:00:17PM +0800, Han Han wrote:
> > > Hello,
> > > I found that the default USB controller for q35 machine type is qemu-xhci
> > > while for pc it is piix3-uhci. Here are the results(on qemu-kvm-7.0.0
> > > qemu-kvm-7.0.0):
> > > ➜ ~ cat /tmp/usb.xml
> > >
> > > USB
> > > 1a81d4ef-6537-4ae8-b257-8a15e0c0525f
> > > 2097152
> > > 2097152
> > > 1
> > >
> > > hvm
> > >
> > >
> > >
> > > /usr/libexec/qemu-kvm
> > >
> > >
> > >
> > > ➜ ~ virsh define /tmp/usb.xml && virsh dumpxml USB|grep usb
> > > Domain 'USB' defined from /tmp/usb.xml
> > >
> > >
> > >
> > >
> > > ➜ ~ cat /tmp/usb-pc.xml
> > >
> > > USB
> > > 1a81d4ef-6537-4ae8-b257-8a15e0c0525f
> > > 2097152
> > > 2097152
> > > 1
> > >
> > > hvm
> > >
> > >
> > >
> > > /usr/libexec/qemu-kvm
> > >
> > >
> > >
> > > ➜ ~ virsh define /tmp/usb-pc.xml && virsh dumpxml USB|grep usb
> > > Domain 'USB' defined from /tmp/usb-pc.xml
> > >
> > >
> > >
> > > And the default usb controller for q35 has been added since:
> > > ed2049ea19 qemu: auto-add generic xhci rather than NEC xhci to Q35
> > domains
> > >
> > > As I know, pc machine supports qemu-xhci as well. Morever, the
> > > performance of qemu-xhci is better than piix3-uhci. So why not update the
> > > default usb controller of pc machine type to qemu-xhci? I think we can
> > > improve it here.
> >
> > A qemu-xhci controller can be added to any x86 machien type regardless
> > of the default, and most mgmt apps will do exactly that.
> >
>
> Does that mean, the default USB controller for a specific x86 machine type
> does NOT matter?
> And leave the default USB controller to up-layer mgmt apps?
Yes, that's our general view for most defaults in fact. There's no
single perfect defaults, so we let mgmt apps select thigns explicitly
With regards,
Daniel
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