Re: [Qemu-devel] [PATCH v2 1/1] target-i386: Fix default Hypervisor level for hypervisor-vendor=kvm.

[Eduardo Habkost]

On Fri, Sep 21, 2012 at 04:26:58PM -0400, Don Slutz wrote:
> On 09/21/12 10:18, Eduardo Habkost wrote:
> >On Thu, Sep 20, 2012 at 04:06:27PM -0400, Don Slutz wrote:
> >> From http://lkml.indiana.edu/hypermail/linux/kernel/1205.0/00100.html
> >>EAX should be KVM_CPUID_FEATURES (0x40000001) not 0.
> >>
> >>Added hypervisor-vendor=kvm0 to get the older CPUID result. kvm1 selects 
> >>the newer one.
> >Why not just make "hypervisor-vendor=kvm" control only the hypervisor
> >vendor string, and support something like "kvm-hypervisor-level=0" to
> >restore the old cpuid_hv_level=0 behavior?
>   -cpu host,hypervisor-vendor=kvm,hypervisor-level=0
> 
>  Does this.

Good.  :-)

> >
> >This is similar to the kvmclock case: it would allow us to make
> >"hypervisor-vendor=kvm" use saner values as default, but letting old
> >machine-types to override it for compatibility if required.
> Right now since I am using env->cpuid_hv_level == 0 as a flag. This
> means that:
> 
>   -cpu host,hypervisor-level=0,hypervisor-vendor=kvm
> 
>   -cpu host,hypervisor-vendor=kvm,hypervisor-level=0
> 
> end up with different CPUID data (Which I do not like). I will fix this in 
> the next round.

Right. This has to be fixed.

> 
> Did you want me to drop kvm0 and kvm1?

Yes, if level is already configurable using the hypervisor-level
property, I don't see the need for kvm0 and kvm1.

If you make kvm_arch_init_vcpu() actually use those fields, you will end
up implementing what's required to allow migration compatibility to be
kept (the only thing missing is to make the CPU class a child of
DeviceState, and add hypervisor-level=0 to the existing machine-types).
:-)

-- 
Eduardo