[Qemu-devel] [PATCH 1/2] allow hypervisor CPUID bit to be overriden

[Qemu-devel] [PATCH 1/2] allow hypervisor CPUID bit to be overriden

[Andre Przywara]

KVM defaults to the hypervisor CPUID bit to be set, whereas pure QEMU clears
it. On some occasions one want to set or clear it the other way round (for
instance to get HyperV running inside a guest).
Allow the default to be overridden on the command line and fix some
whitespace damage on the way.

Signed-off-by: Andre Przywara <andre.przywara@amd.com>
---
 target-i386/helper.c |   25 +++++++++++++------------
 1 files changed, 13 insertions(+), 12 deletions(-)

diff --git a/target-i386/helper.c b/target-i386/helper.c
index 8a76abd..529f962 100644
--- a/target-i386/helper.c
+++ b/target-i386/helper.c
@@ -44,7 +44,7 @@ static const char *ext_feature_name[] = {
     "pni" /* Intel,AMD sse3 */, NULL, NULL, "monitor", "ds_cpl", "vmx", NULL /* Linux smx */, "est",
     "tm2", "ssse3", "cid", NULL, NULL, "cx16", "xtpr", NULL,
     NULL, NULL, "dca", NULL, NULL, NULL, NULL, "popcnt",
-       NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
+    NULL, NULL, NULL, NULL, NULL, NULL, NULL, "hypervisor",
 };
 static const char *ext2_feature_name[] = {
     "fpu", "vme", "de", "pse", "tsc", "msr", "pae", "mce",
@@ -59,30 +59,30 @@ static const char *ext3_feature_name[] = {
     NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
 };
 
-static void add_flagname_to_bitmaps(char *flagname, uint32_t *features, 
-                                    uint32_t *ext_features, 
-                                    uint32_t *ext2_features, 
+static void add_flagname_to_bitmaps(const char *flagname, uint32_t *features,
+                                    uint32_t *ext_features,
+                                    uint32_t *ext2_features,
                                     uint32_t *ext3_features)
 {
     int i;
     int found = 0;
 
-    for ( i = 0 ; i < 32 ; i++ ) 
+    for ( i = 0 ; i < 32 ; i++ )
         if (feature_name[i] && !strcmp (flagname, feature_name[i])) {
             *features |= 1 << i;
             found = 1;
         }
-    for ( i = 0 ; i < 32 ; i++ ) 
+    for ( i = 0 ; i < 32 ; i++ )
         if (ext_feature_name[i] && !strcmp (flagname, ext_feature_name[i])) {
             *ext_features |= 1 << i;
             found = 1;
         }
-    for ( i = 0 ; i < 32 ; i++ ) 
+    for ( i = 0 ; i < 32 ; i++ )
         if (ext2_feature_name[i] && !strcmp (flagname, ext2_feature_name[i])) {
             *ext2_features |= 1 << i;
             found = 1;
         }
-    for ( i = 0 ; i < 32 ; i++ ) 
+    for ( i = 0 ; i < 32 ; i++ )
         if (ext3_feature_name[i] && !strcmp (flagname, ext3_feature_name[i])) {
             *ext3_features |= 1 << i;
             found = 1;
@@ -330,6 +330,11 @@ static int cpu_x86_find_by_name(x86_def_t *x86_cpu_def, const char *cpu_model)
         goto error;
     memcpy(x86_cpu_def, def, sizeof(*def));
 
+    if (kvm_enabled()) {
+        add_flagname_to_bitmaps("hypervisor", &plus_features,
+            &plus_ext_features, &plus_ext2_features, &plus_ext3_features);
+    }
+
     featurestr = strtok(NULL, ",");
 
     while (featurestr) {
@@ -1523,10 +1528,6 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count,
         *ebx = (env->cpuid_apic_id << 24) | 8 << 8; /* CLFLUSH size in quad words, Linux wants it. */
         *ecx = env->cpuid_ext_features;
         *edx = env->cpuid_features;
-
-        /* "Hypervisor present" bit required for Microsoft SVVP */
-        if (kvm_enabled())
-            *ecx |= (1 << 31);
         break;
     case 2:
         /* cache info: needed for Pentium Pro compatibility */
-- 
1.6.1.3

[Qemu-devel] Re: [PATCH 1/2] allow hypervisor CPUID bit to be overriden

[Avi Kivity]

On 06/23/2009 12:47 AM, Andre Przywara wrote:
> KVM defaults to the hypervisor CPUID bit to be set, whereas pure QEMU clears
> it. On some occasions one want to set or clear it the other way round (for
> instance to get HyperV running inside a guest).
> Allow the default to be overridden on the command line and fix some
> whitespace damage on the way.
>    

It makes sense for qemu to set the hypervisor bit unconditionally.  A 
guest running under qemu is not bare metal.

That's a separate change though.  Patch looks good.

-- 
error compiling committee.c: too many arguments to function

Re: [Qemu-devel] Re: [PATCH 1/2] allow hypervisor CPUID bit to be overriden

[Paul Brook]

On Tuesday 23 June 2009, Avi Kivity wrote:
> On 06/23/2009 12:47 AM, Andre Przywara wrote:
> > KVM defaults to the hypervisor CPUID bit to be set, whereas pure QEMU
> > clears it. On some occasions one want to set or clear it the other way
> > round (for instance to get HyperV running inside a guest).
> > Allow the default to be overridden on the command line and fix some
> > whitespace damage on the way.
>
> It makes sense for qemu to set the hypervisor bit unconditionally.  A
> guest running under qemu is not bare metal.

I see no reason why a guest has to be told that it's running inside a VM.
In principle an appropriately configured qemu should be indistinguishable from 
real hardware. In practice it's technically infeasible to cover absolutely 
everything, but if we set this bit we're not even trying.

I have no objection to the bit being set by default for the QEMU CPU types.

Paul

Re: [Qemu-devel] Re: [PATCH 1/2] allow hypervisor CPUID bit to be overriden

[Avi Kivity]

On 06/23/2009 02:31 PM, Paul Brook wrote:
> On Tuesday 23 June 2009, Avi Kivity wrote:
>    
>> On 06/23/2009 12:47 AM, Andre Przywara wrote:
>>      
>>> KVM defaults to the hypervisor CPUID bit to be set, whereas pure QEMU
>>> clears it. On some occasions one want to set or clear it the other way
>>> round (for instance to get HyperV running inside a guest).
>>> Allow the default to be overridden on the command line and fix some
>>> whitespace damage on the way.
>>>        
>> It makes sense for qemu to set the hypervisor bit unconditionally.  A
>> guest running under qemu is not bare metal.
>>      
>
> I see no reason why a guest has to be told that it's running inside a VM.
> In principle an appropriately configured qemu should be indistinguishable from
> real hardware. In practice it's technically infeasible to cover absolutely
> everything, but if we set this bit we're not even trying.
>
> I have no objection to the bit being set by default for the QEMU CPU types.
>    

I agree it's pointless, but it is a Microsoft requirement for passing 
their SVVP tests.  Enabling it by default makes life a little easier for 
users who wish to validate their hypervisor and has no drawbacks.

-- 
error compiling committee.c: too many arguments to function

Re: [Qemu-devel] Re: [PATCH 1/2] allow hypervisor CPUID bit to be overriden

[Paul Brook]

> I agree it's pointless, but it is a Microsoft requirement for passing
> their SVVP tests.  Enabling it by default makes life a little easier for
> users who wish to validate their hypervisor and has no drawbacks.

I wasn't arguing against setting it by default (for QEMU CPU types), just 
against enabling it unconditionally.

Paul

Re: [Qemu-devel] Re: [PATCH 1/2] allow hypervisor CPUID bit to be overriden

[Jamie Lokier]

Avi Kivity wrote:
> On 06/23/2009 02:31 PM, Paul Brook wrote:
> >On Tuesday 23 June 2009, Avi Kivity wrote:
> >   
> >>On 06/23/2009 12:47 AM, Andre Przywara wrote:
> >>     
> >>>KVM defaults to the hypervisor CPUID bit to be set, whereas pure QEMU
> >>>clears it. On some occasions one want to set or clear it the other way
> >>>round (for instance to get HyperV running inside a guest).
> >>>Allow the default to be overridden on the command line and fix some
> >>>whitespace damage on the way.
> >>>       
> >>It makes sense for qemu to set the hypervisor bit unconditionally.  A
> >>guest running under qemu is not bare metal.
> >>     
> >
> >I see no reason why a guest has to be told that it's running inside a VM.
> >In principle an appropriately configured qemu should be indistinguishable 
> >from
> >real hardware. In practice it's technically infeasible to cover absolutely
> >everything, but if we set this bit we're not even trying.
> >
> >I have no objection to the bit being set by default for the QEMU CPU types.
> >   
> 
> I agree it's pointless, but it is a Microsoft requirement for passing 
> their SVVP tests.  Enabling it by default makes life a little easier for 
> users who wish to validate their hypervisor and has no drawbacks.

Hold on.

Do the SVVP tests fail on a real (non-virtal) machine then?

Or is QEMU's machine emulation insufficiently accurate?

I see a drawback in setting the bit by default.

Something I expect from an emulator is that it behaves like a real
machine to the extent possible.  In particular, guest code which
attempts to check if it's running on a real machine should get the
answer "yes".  Unfriendly guest code which pops up a message like
"Sorry I refuse to work for you after 100 hours/ because you are
attempting to run me in a virtual machine, and don't even think of
trying to hide this from me now you know I look for it" should never
do so.

-- Jamie

Re: [Qemu-devel] Re: [PATCH 1/2] allow hypervisor CPUID bit to be overriden

[Gleb Natapov]

On Wed, Jun 24, 2009 at 10:20:41PM +0100, Jamie Lokier wrote:
> Avi Kivity wrote:
> > On 06/23/2009 02:31 PM, Paul Brook wrote:
> > >On Tuesday 23 June 2009, Avi Kivity wrote:
> > >   
> > >>On 06/23/2009 12:47 AM, Andre Przywara wrote:
> > >>     
> > >>>KVM defaults to the hypervisor CPUID bit to be set, whereas pure QEMU
> > >>>clears it. On some occasions one want to set or clear it the other way
> > >>>round (for instance to get HyperV running inside a guest).
> > >>>Allow the default to be overridden on the command line and fix some
> > >>>whitespace damage on the way.
> > >>>       
> > >>It makes sense for qemu to set the hypervisor bit unconditionally.  A
> > >>guest running under qemu is not bare metal.
> > >>     
> > >
> > >I see no reason why a guest has to be told that it's running inside a VM.
> > >In principle an appropriately configured qemu should be indistinguishable 
> > >from
> > >real hardware. In practice it's technically infeasible to cover absolutely
> > >everything, but if we set this bit we're not even trying.
> > >
> > >I have no objection to the bit being set by default for the QEMU CPU types.
> > >   
> > 
> > I agree it's pointless, but it is a Microsoft requirement for passing 
> > their SVVP tests.  Enabling it by default makes life a little easier for 
> > users who wish to validate their hypervisor and has no drawbacks.
> 
> Hold on.
> 
> Do the SVVP tests fail on a real (non-virtal) machine then?
> 
SVVP -> Server Virtualization Validation Program

Definitely fails on a real machine :)

--
			Gleb.

[Qemu-devel] [PATCH 1/2 v2] allow hypervisor CPUID bit to be overriden

[Andre Przywara]

KVM defaults to the hypervisor CPUID bit to be set, whereas pure
QEMU clears it. On some occasions one wants to set or clear it the
other way round (for instance to get HyperV running inside a guest).

Move the bit-set to be done before the command line parsing and
enable it by default. One can disable it by using: -cpu qemu64,-hypervisor
Fix some whitespace damage on the way.

Signed-off-by: Andre Przywara <andre.przywara@amd.com>
---
 target-i386/helper.c |   23 +++++++++++------------
 1 files changed, 11 insertions(+), 12 deletions(-)

diff --git a/target-i386/helper.c b/target-i386/helper.c
index 8a76abd..cb9113e 100644
--- a/target-i386/helper.c
+++ b/target-i386/helper.c
@@ -44,7 +44,7 @@ static const char *ext_feature_name[] = {
     "pni" /* Intel,AMD sse3 */, NULL, NULL, "monitor", "ds_cpl", "vmx", NULL /* Linux smx */, "est",
     "tm2", "ssse3", "cid", NULL, NULL, "cx16", "xtpr", NULL,
     NULL, NULL, "dca", NULL, NULL, NULL, NULL, "popcnt",
-       NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
+    NULL, NULL, NULL, NULL, NULL, NULL, NULL, "hypervisor",
 };
 static const char *ext2_feature_name[] = {
     "fpu", "vme", "de", "pse", "tsc", "msr", "pae", "mce",
@@ -59,30 +59,30 @@ static const char *ext3_feature_name[] = {
     NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
 };
 
-static void add_flagname_to_bitmaps(char *flagname, uint32_t *features, 
-                                    uint32_t *ext_features, 
-                                    uint32_t *ext2_features, 
+static void add_flagname_to_bitmaps(const char *flagname, uint32_t *features,
+                                    uint32_t *ext_features,
+                                    uint32_t *ext2_features,
                                     uint32_t *ext3_features)
 {
     int i;
     int found = 0;
 
-    for ( i = 0 ; i < 32 ; i++ ) 
+    for ( i = 0 ; i < 32 ; i++ )
         if (feature_name[i] && !strcmp (flagname, feature_name[i])) {
             *features |= 1 << i;
             found = 1;
         }
-    for ( i = 0 ; i < 32 ; i++ ) 
+    for ( i = 0 ; i < 32 ; i++ )
         if (ext_feature_name[i] && !strcmp (flagname, ext_feature_name[i])) {
             *ext_features |= 1 << i;
             found = 1;
         }
-    for ( i = 0 ; i < 32 ; i++ ) 
+    for ( i = 0 ; i < 32 ; i++ )
         if (ext2_feature_name[i] && !strcmp (flagname, ext2_feature_name[i])) {
             *ext2_features |= 1 << i;
             found = 1;
         }
-    for ( i = 0 ; i < 32 ; i++ ) 
+    for ( i = 0 ; i < 32 ; i++ )
         if (ext3_feature_name[i] && !strcmp (flagname, ext3_feature_name[i])) {
             *ext3_features |= 1 << i;
             found = 1;
@@ -330,6 +330,9 @@ static int cpu_x86_find_by_name(x86_def_t *x86_cpu_def, const char *cpu_model)
         goto error;
     memcpy(x86_cpu_def, def, sizeof(*def));
 
+    add_flagname_to_bitmaps("hypervisor", &plus_features,
+        &plus_ext_features, &plus_ext2_features, &plus_ext3_features);
+
     featurestr = strtok(NULL, ",");
 
     while (featurestr) {
@@ -1523,10 +1526,6 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count,
         *ebx = (env->cpuid_apic_id << 24) | 8 << 8; /* CLFLUSH size in quad words, Linux wants it. */
         *ecx = env->cpuid_ext_features;
         *edx = env->cpuid_features;
-
-        /* "Hypervisor present" bit required for Microsoft SVVP */
-        if (kvm_enabled())
-            *ecx |= (1 << 31);
         break;
     case 2:
         /* cache info: needed for Pentium Pro compatibility */
-- 
1.6.1.3

[Qemu-devel] Re: [PATCH 1/2 v2] allow hypervisor CPUID bit to be overriden

[Anthony Liguori]

Andre Przywara wrote:
> KVM defaults to the hypervisor CPUID bit to be set, whereas pure
> QEMU clears it. On some occasions one wants to set or clear it the
> other way round (for instance to get HyperV running inside a guest).
>
> Move the bit-set to be done before the command line parsing and
> enable it by default. One can disable it by using: -cpu qemu64,-hypervisor
> Fix some whitespace damage on the way.
>
> Signed-off-by: Andre Przywara <andre.przywara@amd.com>
>
>   
Please also resend 2/2.


-- 
Regards,

Anthony Liguori