Re: [libvirt] [PATCH 1/6] kvm: Add KVM_GET_EMULATED_CPUID
On Fri, Sep 27, 2013 at 11:21:34AM -0300, Eduardo Habkost wrote:
The problem here is that "requested_features" doesn't
include just
the explicit "+flag" flags, but any flag included in the CPU model
definition. See the "-cpu n270" example below.
Oh, you mean if requested_features would contain a flag included from
the CPU model definition - a flag which we haven't requested explicitly
- and if kvm emulates that flag, then it will get enabled?
Hmm.
It should, but your patch will make it stop failing because of MOVBE,
as
now it can be emulated[1].
Right.
"enforce" makes sure all features are really being enabled.
It makes
QEMU abort if there's any feature that can't be enabled on that host.
Ok.
[1] Maybe one source of confusion is that the existing code have two
feature-filtering functions doing basically the same thing:
filter_features_for_kvm() and kvm_check_features_against_host(). That's
Yes, and the first gets executed unconditionally and does the feature
filtering, right after the second has run in the kvm_enabled() branch.
something we must clean up, and they should be unified.
"enforce" should
become synonymous to "make sure filtered_features is all zeroes". This
way, libvirt can emulate what 'enforce" does while being able to collect
detailed error information (which is not easy to do if QEMU simply
aborts).
Ok, maybe someone who's more knowledgeable with this code should do it -
not me :)
Also, there's another aspect, while we're here: now that QEMU emulates
MOVBE with TCG too, how do we specify on the command line, which
emulation should be used - kvm.ko or QEMU?
Thanks.
--
Regards/Gruss,
Boris.
Sent from a fat crate under my desk. Formatting is fine.
--