On Wed, Nov 27, 2019 at 11:10:21AM +0000, Ani Sinha wrote:

Hi :

I see a commit in qemu that adds support for CLZERO but in CPUIDs. :

commit e900135dcfb676a4019dc206395e02db5d1de0d6
Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Wed Sep 25 23:49:48 2019 +0200

i386: Add CPUID bit for CLZERO and XSAVEERPTR

The CPUID bits CLZERO and XSAVEERPTR are availble on AMD's ZEN platform
and could be passed to the guest.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Is there a corresponding change in libvirt adding this capability? Libvirt complains when I add it manually in the vm xml:

# virsh create newvm.xml
error: Failed to create domain from newvm.xml
error: unsupported configuration: unknown CPU feature: clzero

# grep clzero newvm.xml
<feature policy='require' name='clzero'/>

Should we add it?

Yes, if it is supported by QEMU to expose to a guest, then it should be
added to libvirt too.

Presumably only needs add an addition to src/cpu_maps/x86_features.xml

Regards,
Daniel
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