Re: [Qemu-devel] [RFC PATCH] kvm: Enable -cpu option to hide KVM

[Alex Williamson <alex.williamson@redhat.com>]

On Sun, 2014-06-01 at 20:29 +0200, Paolo Bonzini wrote:
> Il 01/06/2014 18:25, Alex Williamson ha scritto:
> > The latest Nvidia driver (337.88) specifically checks for KVM as the
> > hypervisor and reports Code 43 for the driver in a Windows guest when
> > found.  Removing or changing the KVM signature is sufficient to allow
> > the driver to load.  This patch adds an option to easily allow the KVM
> > hypervisor signature to be hidden using '-cpu no-kvm'.
> >
> > Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> 
> It's really a nit, but I think "kvm=no" is preferrable (more consistent 
> with how hyper-v leaves are enabled).

Happy to oblige, but I'm not sure what I'm looking for.  We enably
hyper-v leaves if hyperv_enabled(), which seems to boil down to the kvm
kernel supporting KVM_CAP_HYPERV and one or more cpu->hyperv_foo
features enabled.  What's the commandline option I'm looking for that
has some sort of hyper-v=on|off?  Thanks,

Alex

> > ---
> >  target-i386/cpu-qom.h |    1 +
> >  target-i386/cpu.c     |    1 +
> >  target-i386/kvm.c     |   28 +++++++++++++++-------------
> >  3 files changed, 17 insertions(+), 13 deletions(-)
> >
> > diff --git a/target-i386/cpu-qom.h b/target-i386/cpu-qom.h
> > index e9b3d57..99bb059 100644
> > --- a/target-i386/cpu-qom.h
> > +++ b/target-i386/cpu-qom.h
> > @@ -87,6 +87,7 @@ typedef struct X86CPU {
> >      bool hyperv_time;
> >      bool check_cpuid;
> >      bool enforce_cpuid;
> > +    bool no_kvm;
> >
> >      /* if true the CPUID code directly forward host cache leaves to the guest */
> >      bool cache_info_passthrough;
> > diff --git a/target-i386/cpu.c b/target-i386/cpu.c
> > index 042a48d..8e6ce9c 100644
> > --- a/target-i386/cpu.c
> > +++ b/target-i386/cpu.c
> > @@ -2792,6 +2792,7 @@ static Property x86_cpu_properties[] = {
> >      DEFINE_PROP_BOOL("hv-time", X86CPU, hyperv_time, false),
> >      DEFINE_PROP_BOOL("check", X86CPU, check_cpuid, false),
> >      DEFINE_PROP_BOOL("enforce", X86CPU, enforce_cpuid, false),
> > +    DEFINE_PROP_BOOL("no-kvm", X86CPU, no_kvm, false),
> >      DEFINE_PROP_END_OF_LIST()
> >  };
> >
> > diff --git a/target-i386/kvm.c b/target-i386/kvm.c
> > index 0d894ef..920898e 100644
> > --- a/target-i386/kvm.c
> > +++ b/target-i386/kvm.c
> > @@ -528,23 +528,25 @@ int kvm_arch_init_vcpu(CPUState *cs)
> >          has_msr_hv_hypercall = true;
> >      }
> >
> > -    memcpy(signature, "KVMKVMKVM\0\0\0", 12);
> > -    c = &cpuid_data.entries[cpuid_i++];
> > -    c->function = KVM_CPUID_SIGNATURE | kvm_base;
> > -    c->eax = 0;
> > -    c->ebx = signature[0];
> > -    c->ecx = signature[1];
> > -    c->edx = signature[2];
> > +    if (!cpu->no_kvm) {
> > +        memcpy(signature, "KVMKVMKVM\0\0\0", 12);
> > +        c = &cpuid_data.entries[cpuid_i++];
> > +        c->function = KVM_CPUID_SIGNATURE | kvm_base;
> > +        c->eax = 0;
> > +        c->ebx = signature[0];
> > +        c->ecx = signature[1];
> > +        c->edx = signature[2];
> >
> > -    c = &cpuid_data.entries[cpuid_i++];
> > -    c->function = KVM_CPUID_FEATURES | kvm_base;
> > -    c->eax = env->features[FEAT_KVM];
> > +        c = &cpuid_data.entries[cpuid_i++];
> > +        c->function = KVM_CPUID_FEATURES | kvm_base;
> > +        c->eax = env->features[FEAT_KVM];
> >
> > -    has_msr_async_pf_en = c->eax & (1 << KVM_FEATURE_ASYNC_PF);
> > +        has_msr_async_pf_en = c->eax & (1 << KVM_FEATURE_ASYNC_PF);
> >
> > -    has_msr_pv_eoi_en = c->eax & (1 << KVM_FEATURE_PV_EOI);
> > +        has_msr_pv_eoi_en = c->eax & (1 << KVM_FEATURE_PV_EOI);
> >
> > -    has_msr_kvm_steal_time = c->eax & (1 << KVM_FEATURE_STEAL_TIME);
> > +        has_msr_kvm_steal_time = c->eax & (1 << KVM_FEATURE_STEAL_TIME);
> > +    }
> >
> >      cpu_x86_cpuid(env, 0, 0, &limit, &unused, &unused, &unused);
> >
> >
> > --
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