kvm: Enable -cpu option to hide KVM

Message ID	20140602172811.13457.57010.stgit@bling.home (mailing list archive)
State	New, archived
Headers	show Return-Path: <kvm-owner@kernel.org> Subject: [PATCH] kvm: Enable -cpu option to hide KVM From: Alex Williamson <alex.williamson@redhat.com> To: qemu-devel@nongnu.org Cc: pbonzini@redhat.com, kvm@vger.kernel.org Date: Mon, 02 Jun 2014 11:28:50 -0600 Message-ID: <20140602172811.13457.57010.stgit@bling.home> User-Agent: StGit/0.17-dirty MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: kvm-owner@vger.kernel.org Precedence: bulk

Message ID

20140602172811.13457.57010.stgit@bling.home (mailing list archive)

State

New, archived

Headers

Subject: [PATCH] kvm: Enable -cpu option to hide KVM
From: Alex Williamson <alex.williamson@redhat.com>
To: qemu-devel@nongnu.org
Cc: pbonzini@redhat.com, kvm@vger.kernel.org
Date: Mon, 02 Jun 2014 11:28:50 -0600
Message-ID: <20140602172811.13457.57010.stgit@bling.home>
User-Agent: StGit/0.17-dirty
MIME-Version: 1.0
Content-Type: text/plain; charset="utf-8"
Content-Transfer-Encoding: 7bit
Sender: kvm-owner@vger.kernel.org
Precedence: bulk

Commit Message

Alex Williamson June 2, 2014, 5:28 p.m. UTC

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 for the
driver to load and work.  This patch adds an option to easily allow
the KVM hypervisor signature to be hidden using '-cpu kvm=off'.  We
continue to expose KVM via the cpuid value by default.  The state of
this option does not supercede or replace -enable-kvm or the accel=kvm
machine option.  This only changes the visibility of KVM to the guest
and paravirtual features specifically tied to the KVM cpuid.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---
 target-i386/cpu-qom.h |    1 +
 target-i386/cpu.c     |    1 +
 target-i386/kvm.c     |   28 +++++++++++++++-------------
 3 files changed, 17 insertions(+), 13 deletions(-)


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Comments

Bandan Das June 2, 2014, 7:09 p.m. UTC | #1

Alex Williamson <alex.williamson@redhat.com> writes:

> 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 for the
> driver to load and work.  This patch adds an option to easily allow
> the KVM hypervisor signature to be hidden using '-cpu kvm=off'.  We
> continue to expose KVM via the cpuid value by default.  The state of
> this option does not supercede or replace -enable-kvm or the accel=kvm
> machine option.  This only changes the visibility of KVM to the guest
> and paravirtual features specifically tied to the KVM cpuid.
>
> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> ---
>  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..0808cfc 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 expose_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..cbf1d97 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("kvm", X86CPU, expose_kvm, true),
>      DEFINE_PROP_END_OF_LIST()
>  };
>  
> diff --git a/target-i386/kvm.c b/target-i386/kvm.c
> index 0d894ef..b2295d2 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->expose_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);
Does this mean that we don't expose these features if kvm=off is 
specified ?

> +    }
>  
>      cpu_x86_cpuid(env, 0, 0, &limit, &unused, &unused, &unused);
>  
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Alex Williamson June 2, 2014, 7:17 p.m. UTC | #2

On Mon, 2014-06-02 at 15:09 -0400, Bandan Das wrote:
> Alex Williamson <alex.williamson@redhat.com> writes:
> 
> > 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 for the
> > driver to load and work.  This patch adds an option to easily allow
> > the KVM hypervisor signature to be hidden using '-cpu kvm=off'.  We
> > continue to expose KVM via the cpuid value by default.  The state of
> > this option does not supercede or replace -enable-kvm or the accel=kvm
> > machine option.  This only changes the visibility of KVM to the guest
> > and paravirtual features specifically tied to the KVM cpuid.
> >
> > Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> > ---
> >  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..0808cfc 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 expose_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..cbf1d97 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("kvm", X86CPU, expose_kvm, true),
> >      DEFINE_PROP_END_OF_LIST()
> >  };
> >  
> > diff --git a/target-i386/kvm.c b/target-i386/kvm.c
> > index 0d894ef..b2295d2 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->expose_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);
> Does this mean that we don't expose these features if kvm=off is 
> specified ?

Correct, the guest would only learn about them via the bits in this
cpuid return value, so it should not be making use of them when kvm=off.
Thanks,

Alex

> 
> > +    }
> >  
> >      cpu_x86_cpuid(env, 0, 0, &limit, &unused, &unused, &unused);
> >  



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Paolo Bonzini June 3, 2014, 9:21 a.m. UTC | #3

Il 02/06/2014 19:28, 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 for the
> driver to load and work.  This patch adds an option to easily allow
> the KVM hypervisor signature to be hidden using '-cpu kvm=off'.  We
> continue to expose KVM via the cpuid value by default.  The state of
> this option does not supercede or replace -enable-kvm or the accel=kvm
> machine option.  This only changes the visibility of KVM to the guest
> and paravirtual features specifically tied to the KVM cpuid.
>
> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> ---
>  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..0808cfc 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 expose_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..cbf1d97 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("kvm", X86CPU, expose_kvm, true),
>      DEFINE_PROP_END_OF_LIST()
>  };
>
> diff --git a/target-i386/kvm.c b/target-i386/kvm.c
> index 0d894ef..b2295d2 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->expose_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);
>
>

Applying to uq/master, thanks.

Paolo
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diff --git a/target-i386/cpu-qom.h b/target-i386/cpu-qom.h
index e9b3d57..0808cfc 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 expose_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..cbf1d97 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("kvm", X86CPU, expose_kvm, true),
     DEFINE_PROP_END_OF_LIST()
 };
 
diff --git a/target-i386/kvm.c b/target-i386/kvm.c
index 0d894ef..b2295d2 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->expose_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);

kvm: Enable -cpu option to hide KVM

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