[libvirt] kvm: "warning: host doesn't support requested feature: CPUID.01H:ECX.x2apic [bit 21]"

[Eduardo Habkost]

(CCing libvir-list)

On Sat, Feb 20, 2016 at 04:00:30AM -0500, Paolo Bonzini wrote:
> ----- Original Message -----
> > From: "Jan Kiszka" <jan.kiszka at web.de>
> > To: "Eduardo Habkost" <ehabkost at redhat.com>, "Paolo Bonzini" <pbonzini at redhat.com>
> > Cc: "qemu-devel" <qemu-devel at nongnu.org>, "kvm" <kvm at vger.kernel.org>
> > Sent: Saturday, February 20, 2016 9:09:32 AM
> > Subject: kvm: "warning: host doesn't support requested feature: CPUID.01H:ECX.x2apic [bit 21]"
> > 
> > Hi all,
> > 
> > I suppose 5120901a37 introduced this: qemu with kernel_irqchip=off now
> > generates these warnings, one per VCPU, during QEMU startup. Is the plan
> > to live with them until we finally have x2APIC emulation in userspace
> > (ie. also MSR vmexiting to there), or should we otherwise avoid it?
> 
> I think it's a bug, x2apic should be auto-suppressed with kernel_irqchip=off.

My first reaction is to dislike the idea of adding yet another
variable that affects the results of CPU models.

But considering that we are moving towards a design where libvirt
must not assume or query any low-level detail from CPU models at
all, maybe this won't be harmful.

-- 
Eduardo