[libvirt] [QEMU PATCH] target-i386: Disable rdtscp on Opteron_G* CPU models

Eduardo Habkost ehabkost at redhat.com
Mon Nov 16 13:19:32 UTC 2015

On Mon, Nov 16, 2015 at 10:44:59AM +0100, Paolo Bonzini wrote:
> On 13/11/2015 20:07, Eduardo Habkost wrote:
> > KVM can't virtualize rdtscp on AMD CPUs yet, so there's no point
> > in enabling it by default on AMD CPU models, as all we are
> > getting are confused users because of the "host doesn't support
> > requested feature" warnings.
> > 
> > Disable rdtscp on Opteron_G* models, but keep compatibility on
> > pc-*-2.4 and older (just in case there are people are doing funny
> > stuff using AMD CPU models on Intel hosts).
> > 
> > Signed-off-by: Eduardo Habkost <ehabkost at redhat.com>
> Can we do it only on KVM and not on TCG?

We can, but I would like to avoid it, if possible. It would
require more complex compat code (the "Add optional class name to
kvm_default_props¨ patch I sent some time ago), and people who
need rdtscp will be able to use Opteron_G*-rdtscp soon.


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