Re: [Qemu-devel] [PATCH 1/1] cpu: report hyperv feature words through qom

[Eduardo Habkost]

On Tue, Jun 14, 2016 at 11:45:08PM +0300, Denis V. Lunev wrote:
> On 06/14/2016 10:59 PM, Eduardo Habkost wrote:
> > On Tue, Jun 14, 2016 at 01:28:40PM +0300, Denis V. Lunev wrote:
> > > From: Evgeny Yakovlev <address@hidden>
> > > 
> > > This change adds hyperv feature words report through qom rpc.
> > > 
> > > When VM is configured with hyperv features enabled libvirt will check that
> > > required featured words are set in cpuid leaf 40000003 through qom
> > > request.
> > > 
> > > Currently qemu does not report hyperv feature words which prevents windows
> > > guests from starting with libvirt.
> > > 
> > > Signed-off-by: Evgeny Yakovlev <address@hidden>
> > > Signed-off-by: Denis V. Lunev <address@hidden>
> > > CC: Paolo Bonzini <address@hidden>
> > > CC: Richard Henderson <address@hidden>
> > > CC: Eduardo Habkost <address@hidden>
> > > CC: Marcelo Tosatti <address@hidden>
> > Which QEMU version did you use to test this? Some of those properties 
> > already
> > exist. See:
> > 
> >    static Property x86_cpu_properties[] = {
> >        [...]
> >        { .name  = "hv-spinlocks", .info  = &qdev_prop_spinlocks },
> >        DEFINE_PROP_BOOL("hv-relaxed", X86CPU, hyperv_relaxed_timing, false),
> >        DEFINE_PROP_BOOL("hv-vapic", X86CPU, hyperv_vapic, false),
> >        DEFINE_PROP_BOOL("hv-time", X86CPU, hyperv_time, false),
> >        DEFINE_PROP_BOOL("hv-crash", X86CPU, hyperv_crash, false),
> >        DEFINE_PROP_BOOL("hv-reset", X86CPU, hyperv_reset, false),
> >        DEFINE_PROP_BOOL("hv-vpindex", X86CPU, hyperv_vpindex, false),
> >        DEFINE_PROP_BOOL("hv-runtime", X86CPU, hyperv_runtime, false),
> >        DEFINE_PROP_BOOL("hv-synic", X86CPU, hyperv_synic, false),
> >        DEFINE_PROP_BOOL("hv-stimer", X86CPU, hyperv_stimer, false),
> >        [...]
> >        DEFINE_PROP_STRING("hv-vendor-id", X86CPU, hyperv_vendor_id),
> >        DEFINE_PROP_END_OF_LIST()
> >    };
> > 
> > QEMU will crash if you try to register the properties twice:
> > 
> >    $ ./x86_64-softmmu/qemu-system-x86_64
> >    qemu-system-x86_64: 
> > /home/ehabkost/rh/proj/virt/qemu/target-i386/cpu.c:3094: 
> > x86_cpu_register_bit_prop: Assertion `fp->ptr == field' failed.
> >    Aborted (core dumped)
> > 
> > I like the idea of moving hyperv feature information inside the features 
> > array,
> > though.
> no, idea is a bit different.
> 
> The user selects properties in the command line to enable
> different HyperV enlightenments. This is how we do that
> and this is how the QEMU is expected to work.
> 
> After that libvirt starts to check that these properties do
> work. In order to do that it executes qom-get and expects
> to find enabled HyperV enlightenments in the guest CPUID.
> 
> This is the idea of this patch.

And why exactly moving hyperv feature information inside the
CPUX86State::features array wouldn't do exactly what you say
above?

-- 
Eduardo