Patchwork [qom-cpu,10/11] target-i386: Call kvm_check_features_against_host() only if CONFIG_KVM is set

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Submitter Eduardo Habkost
Date Jan. 4, 2013, 10:01 p.m.
Message ID <1357336872-7200-11-git-send-email-ehabkost@redhat.com>
Download mbox | patch
Permalink /patch/209554/
State New
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Comments

Eduardo Habkost - Jan. 4, 2013, 10:01 p.m.
This will be necessary once kvm_check_features_against_host() starts
using KVM-specific definitions (so it won't compile anymore if
CONFIG_KVM is not set).

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
---
 target-i386/cpu.c | 4 ++++
 1 file changed, 4 insertions(+)
Gleb Natapov - Jan. 6, 2013, 2:27 p.m.
On Fri, Jan 04, 2013 at 08:01:11PM -0200, Eduardo Habkost wrote:
> This will be necessary once kvm_check_features_against_host() starts
> using KVM-specific definitions (so it won't compile anymore if
> CONFIG_KVM is not set).
> 
> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> ---
>  target-i386/cpu.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/target-i386/cpu.c b/target-i386/cpu.c
> index 1c3c7e1..876b0f6 100644
> --- a/target-i386/cpu.c
> +++ b/target-i386/cpu.c
> @@ -936,6 +936,7 @@ static void kvm_cpu_fill_host(x86_def_t *x86_cpu_def)
>  #endif /* CONFIG_KVM */
>  }
>  
> +#ifdef CONFIG_KVM
>  static int unavailable_host_feature(struct model_features_t *f, uint32_t mask)
>  {
>      int i;
> @@ -987,6 +988,7 @@ static int kvm_check_features_against_host(x86_def_t *guest_def)
>                  }
>      return rv;
>  }
> +#endif
>  
>  static void x86_cpuid_version_get_family(Object *obj, Visitor *v, void *opaque,
>                                           const char *name, Error **errp)
> @@ -1410,10 +1412,12 @@ static int cpu_x86_parse_featurestr(x86_def_t *x86_cpu_def, char *features)
>      x86_cpu_def->kvm_features &= ~minus_kvm_features;
>      x86_cpu_def->svm_features &= ~minus_svm_features;
>      x86_cpu_def->cpuid_7_0_ebx_features &= ~minus_7_0_ebx_features;
> +#ifdef CONFIG_KVM
>      if (check_cpuid && kvm_enabled()) {
>          if (kvm_check_features_against_host(x86_cpu_def) && enforce_cpuid)
>              goto error;
>      }
> +#endif
Provide kvm_check_features_against_host() stub if !CONFIG_KVM and drop
ifdef here.

>      return 0;
>  
>  error:
> -- 
> 1.7.11.7
> 

--
			Gleb.
Eduardo Habkost - Jan. 7, 2013, noon
On Sun, Jan 06, 2013 at 04:27:19PM +0200, Gleb Natapov wrote:
> On Fri, Jan 04, 2013 at 08:01:11PM -0200, Eduardo Habkost wrote:
> > This will be necessary once kvm_check_features_against_host() starts
> > using KVM-specific definitions (so it won't compile anymore if
> > CONFIG_KVM is not set).
> > 
> > Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> > ---
> >  target-i386/cpu.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> > 
> > diff --git a/target-i386/cpu.c b/target-i386/cpu.c
> > index 1c3c7e1..876b0f6 100644
> > --- a/target-i386/cpu.c
> > +++ b/target-i386/cpu.c
> > @@ -936,6 +936,7 @@ static void kvm_cpu_fill_host(x86_def_t *x86_cpu_def)
> >  #endif /* CONFIG_KVM */
> >  }
> >  
> > +#ifdef CONFIG_KVM
> >  static int unavailable_host_feature(struct model_features_t *f, uint32_t mask)
> >  {
> >      int i;
> > @@ -987,6 +988,7 @@ static int kvm_check_features_against_host(x86_def_t *guest_def)
> >                  }
> >      return rv;
> >  }
> > +#endif
> >  
> >  static void x86_cpuid_version_get_family(Object *obj, Visitor *v, void *opaque,
> >                                           const char *name, Error **errp)
> > @@ -1410,10 +1412,12 @@ static int cpu_x86_parse_featurestr(x86_def_t *x86_cpu_def, char *features)
> >      x86_cpu_def->kvm_features &= ~minus_kvm_features;
> >      x86_cpu_def->svm_features &= ~minus_svm_features;
> >      x86_cpu_def->cpuid_7_0_ebx_features &= ~minus_7_0_ebx_features;
> > +#ifdef CONFIG_KVM
> >      if (check_cpuid && kvm_enabled()) {
> >          if (kvm_check_features_against_host(x86_cpu_def) && enforce_cpuid)
> >              goto error;
> >      }
> > +#endif
> Provide kvm_check_features_against_host() stub if !CONFIG_KVM and drop
> ifdef here.

I will do. Igor probably will have to change his "target-i386: move
kvm_check_features_against_host() check to realize time" patch to use
the same approach, too.
Igor Mammedov - Jan. 7, 2013, 1:15 p.m.
On Mon, 7 Jan 2013 10:00:09 -0200
Eduardo Habkost <ehabkost@redhat.com> wrote:

> On Sun, Jan 06, 2013 at 04:27:19PM +0200, Gleb Natapov wrote:
> > On Fri, Jan 04, 2013 at 08:01:11PM -0200, Eduardo Habkost wrote:
> > > This will be necessary once kvm_check_features_against_host() starts
> > > using KVM-specific definitions (so it won't compile anymore if
> > > CONFIG_KVM is not set).
> > > 
> > > Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> > > ---
> > >  target-i386/cpu.c | 4 ++++
> > >  1 file changed, 4 insertions(+)
> > > 
> > > diff --git a/target-i386/cpu.c b/target-i386/cpu.c
> > > index 1c3c7e1..876b0f6 100644
> > > --- a/target-i386/cpu.c
> > > +++ b/target-i386/cpu.c
> > > @@ -936,6 +936,7 @@ static void kvm_cpu_fill_host(x86_def_t *x86_cpu_def)
> > >  #endif /* CONFIG_KVM */
> > >  }
> > >  
> > > +#ifdef CONFIG_KVM
> > >  static int unavailable_host_feature(struct model_features_t *f, uint32_t mask)
> > >  {
> > >      int i;
> > > @@ -987,6 +988,7 @@ static int kvm_check_features_against_host(x86_def_t *guest_def)
> > >                  }
> > >      return rv;
> > >  }
> > > +#endif
> > >  
> > >  static void x86_cpuid_version_get_family(Object *obj, Visitor *v, void *opaque,
> > >                                           const char *name, Error **errp)
> > > @@ -1410,10 +1412,12 @@ static int cpu_x86_parse_featurestr(x86_def_t *x86_cpu_def, char *features)
> > >      x86_cpu_def->kvm_features &= ~minus_kvm_features;
> > >      x86_cpu_def->svm_features &= ~minus_svm_features;
> > >      x86_cpu_def->cpuid_7_0_ebx_features &= ~minus_7_0_ebx_features;
> > > +#ifdef CONFIG_KVM
> > >      if (check_cpuid && kvm_enabled()) {
> > >          if (kvm_check_features_against_host(x86_cpu_def) && enforce_cpuid)
> > >              goto error;
> > >      }
> > > +#endif
> > Provide kvm_check_features_against_host() stub if !CONFIG_KVM and drop
> > ifdef here.
> 
> I will do. Igor probably will have to change his "target-i386: move
> kvm_check_features_against_host() check to realize time" patch to use
> the same approach, too.


Gleb,

Why do stub here? As result we will be adding more ifdef-s just in other
places. Currently kvm_cpu_fill_host(), unavailable_host_feature() and
kvm_check_features_against_host() are bundled together in cpu.c so we could
instead ifdef whole block. Like here:
http://www.mail-archive.com/qemu-devel@nongnu.org/msg146536.html

For me code looks more readable with ifdef here, if we have stub, a reader
would have to look at kvm_check_features_against_host() body to see if it does
anything.

> 
> -- 
> Eduardo
>
Gleb Natapov - Jan. 7, 2013, 1:30 p.m.
On Mon, Jan 07, 2013 at 02:15:14PM +0100, Igor Mammedov wrote:
> On Mon, 7 Jan 2013 10:00:09 -0200
> Eduardo Habkost <ehabkost@redhat.com> wrote:
> 
> > On Sun, Jan 06, 2013 at 04:27:19PM +0200, Gleb Natapov wrote:
> > > On Fri, Jan 04, 2013 at 08:01:11PM -0200, Eduardo Habkost wrote:
> > > > This will be necessary once kvm_check_features_against_host() starts
> > > > using KVM-specific definitions (so it won't compile anymore if
> > > > CONFIG_KVM is not set).
> > > > 
> > > > Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> > > > ---
> > > >  target-i386/cpu.c | 4 ++++
> > > >  1 file changed, 4 insertions(+)
> > > > 
> > > > diff --git a/target-i386/cpu.c b/target-i386/cpu.c
> > > > index 1c3c7e1..876b0f6 100644
> > > > --- a/target-i386/cpu.c
> > > > +++ b/target-i386/cpu.c
> > > > @@ -936,6 +936,7 @@ static void kvm_cpu_fill_host(x86_def_t *x86_cpu_def)
> > > >  #endif /* CONFIG_KVM */
> > > >  }
> > > >  
> > > > +#ifdef CONFIG_KVM
> > > >  static int unavailable_host_feature(struct model_features_t *f, uint32_t mask)
> > > >  {
> > > >      int i;
> > > > @@ -987,6 +988,7 @@ static int kvm_check_features_against_host(x86_def_t *guest_def)
> > > >                  }
> > > >      return rv;
> > > >  }
> > > > +#endif
> > > >  
> > > >  static void x86_cpuid_version_get_family(Object *obj, Visitor *v, void *opaque,
> > > >                                           const char *name, Error **errp)
> > > > @@ -1410,10 +1412,12 @@ static int cpu_x86_parse_featurestr(x86_def_t *x86_cpu_def, char *features)
> > > >      x86_cpu_def->kvm_features &= ~minus_kvm_features;
> > > >      x86_cpu_def->svm_features &= ~minus_svm_features;
> > > >      x86_cpu_def->cpuid_7_0_ebx_features &= ~minus_7_0_ebx_features;
> > > > +#ifdef CONFIG_KVM
> > > >      if (check_cpuid && kvm_enabled()) {
> > > >          if (kvm_check_features_against_host(x86_cpu_def) && enforce_cpuid)
> > > >              goto error;
> > > >      }
> > > > +#endif
> > > Provide kvm_check_features_against_host() stub if !CONFIG_KVM and drop
> > > ifdef here.
> > 
> > I will do. Igor probably will have to change his "target-i386: move
> > kvm_check_features_against_host() check to realize time" patch to use
> > the same approach, too.
> 
> 
> Gleb,
> 
> Why do stub here? As result we will be adding more ifdef-s just in other
> places. Currently kvm_cpu_fill_host(), unavailable_host_feature() and
Why will we be adding more ifdef-s in other places?

> kvm_check_features_against_host() are bundled together in cpu.c so we could
> instead ifdef whole block. Like here:
> http://www.mail-archive.com/qemu-devel@nongnu.org/msg146536.html
> 
That's fine, but you can avoid things like:

     if (kvm_enabled() && name && strcmp(name, "host") == 0) {
+#ifdef CONFIG_KVM
         kvm_cpu_fill_host(x86_cpu_def);
+#endif

in your patch by providing stub for kvm_cpu_fill_host() for !CONFIG_KVM
case. This is common practice really. Avoid ifdefs in the code.

> For me code looks more readable with ifdef here, if we have stub, a reader
> would have to look at kvm_check_features_against_host() body to see if it does
> anything.
> 
If reader cares about kvm it has to anyway. If he does not, there is
friendly kvm_enabled() (which is stub in case of !CONFIG_KVM BTW) to
tell him that he does not care. No need additional ifdef there.

--
			Gleb.
Eduardo Habkost - Jan. 7, 2013, 1:30 p.m.
On Mon, Jan 07, 2013 at 02:15:14PM +0100, Igor Mammedov wrote:
> On Mon, 7 Jan 2013 10:00:09 -0200
> Eduardo Habkost <ehabkost@redhat.com> wrote:
> 
> > On Sun, Jan 06, 2013 at 04:27:19PM +0200, Gleb Natapov wrote:
> > > On Fri, Jan 04, 2013 at 08:01:11PM -0200, Eduardo Habkost wrote:
> > > > This will be necessary once kvm_check_features_against_host() starts
> > > > using KVM-specific definitions (so it won't compile anymore if
> > > > CONFIG_KVM is not set).
> > > > 
> > > > Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> > > > ---
> > > >  target-i386/cpu.c | 4 ++++
> > > >  1 file changed, 4 insertions(+)
> > > > 
> > > > diff --git a/target-i386/cpu.c b/target-i386/cpu.c
> > > > index 1c3c7e1..876b0f6 100644
> > > > --- a/target-i386/cpu.c
> > > > +++ b/target-i386/cpu.c
> > > > @@ -936,6 +936,7 @@ static void kvm_cpu_fill_host(x86_def_t *x86_cpu_def)
> > > >  #endif /* CONFIG_KVM */
> > > >  }
> > > >  
> > > > +#ifdef CONFIG_KVM
> > > >  static int unavailable_host_feature(struct model_features_t *f, uint32_t mask)
> > > >  {
> > > >      int i;
> > > > @@ -987,6 +988,7 @@ static int kvm_check_features_against_host(x86_def_t *guest_def)
> > > >                  }
> > > >      return rv;
> > > >  }
> > > > +#endif
> > > >  
> > > >  static void x86_cpuid_version_get_family(Object *obj, Visitor *v, void *opaque,
> > > >                                           const char *name, Error **errp)
> > > > @@ -1410,10 +1412,12 @@ static int cpu_x86_parse_featurestr(x86_def_t *x86_cpu_def, char *features)
> > > >      x86_cpu_def->kvm_features &= ~minus_kvm_features;
> > > >      x86_cpu_def->svm_features &= ~minus_svm_features;
> > > >      x86_cpu_def->cpuid_7_0_ebx_features &= ~minus_7_0_ebx_features;
> > > > +#ifdef CONFIG_KVM
> > > >      if (check_cpuid && kvm_enabled()) {
> > > >          if (kvm_check_features_against_host(x86_cpu_def) && enforce_cpuid)
> > > >              goto error;
> > > >      }
> > > > +#endif
> > > Provide kvm_check_features_against_host() stub if !CONFIG_KVM and drop
> > > ifdef here.
> > 
> > I will do. Igor probably will have to change his "target-i386: move
> > kvm_check_features_against_host() check to realize time" patch to use
> > the same approach, too.
> 
> 
> Gleb,
> 
> Why do stub here? As result we will be adding more ifdef-s just in other
> places. Currently kvm_cpu_fill_host(), unavailable_host_feature() and
> kvm_check_features_against_host() are bundled together in cpu.c so we could
> instead ifdef whole block. Like here:
> http://www.mail-archive.com/qemu-devel@nongnu.org/msg146536.html
> 
> For me code looks more readable with ifdef here, if we have stub, a reader
> would have to look at kvm_check_features_against_host() body to see if it does
> anything.

If CONFIG_KVM is not set, kvm_enabled() is always zero, so the function
would never be called, so I find the ifdef-less code more readable and
obvious.

What I don't know is if we should do this:

  #ifdef CONFIG_KVM
  
  static int kvm_check_features_against_host(...)
  {
      /* real implementation here */
  }
  
  static int kvm_do_something_else(...)
  {
      /* real implementation here */
  }
  
  /* Other kvm_* functions here */
  
  #else
  
  static int kvm_check_features_against_host(...)
  {
  }
  
  static int kvm_do_something_else(...)
  {
  }
  
  /* Other kvm_* stubs here */
  
  #endif /* CONFIG_KVM */


Or this:

  static int kvm_check_features_against_host(...)
  {
  #ifdef CONFIG_KVM
      /* real implementation here */
  #endif /* CONFIG_KVM */
  }
  
  static int kvm_do_something_else(...)
  {
  #ifdef CONFIG_KVM
      /* real implementation here */
  #endif /* CONFIG_KVM */
  }


I believe the latter is better, but based on Gleb's comments about
enable_kvm_pv_eoi(), he seems to prefer the former.
Igor Mammedov - Jan. 7, 2013, 2:13 p.m.
On Mon, 7 Jan 2013 15:30:26 +0200
Gleb Natapov <gleb@redhat.com> wrote:

> On Mon, Jan 07, 2013 at 02:15:14PM +0100, Igor Mammedov wrote:
> > On Mon, 7 Jan 2013 10:00:09 -0200
> > Eduardo Habkost <ehabkost@redhat.com> wrote:
> > 
> > > On Sun, Jan 06, 2013 at 04:27:19PM +0200, Gleb Natapov wrote:
> > > > On Fri, Jan 04, 2013 at 08:01:11PM -0200, Eduardo Habkost wrote:
> > > > > This will be necessary once kvm_check_features_against_host() starts
> > > > > using KVM-specific definitions (so it won't compile anymore if
> > > > > CONFIG_KVM is not set).
> > > > > 
> > > > > Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> > > > > ---
> > > > >  target-i386/cpu.c | 4 ++++
> > > > >  1 file changed, 4 insertions(+)
> > > > > 
> > > > > diff --git a/target-i386/cpu.c b/target-i386/cpu.c
> > > > > index 1c3c7e1..876b0f6 100644
> > > > > --- a/target-i386/cpu.c
> > > > > +++ b/target-i386/cpu.c
> > > > > @@ -936,6 +936,7 @@ static void kvm_cpu_fill_host(x86_def_t *x86_cpu_def)
> > > > >  #endif /* CONFIG_KVM */
> > > > >  }
> > > > >  
> > > > > +#ifdef CONFIG_KVM
> > > > >  static int unavailable_host_feature(struct model_features_t *f, uint32_t mask)
> > > > >  {
> > > > >      int i;
> > > > > @@ -987,6 +988,7 @@ static int kvm_check_features_against_host(x86_def_t *guest_def)
> > > > >                  }
> > > > >      return rv;
> > > > >  }
> > > > > +#endif
> > > > >  
> > > > >  static void x86_cpuid_version_get_family(Object *obj, Visitor *v, void *opaque,
> > > > >                                           const char *name, Error **errp)
> > > > > @@ -1410,10 +1412,12 @@ static int cpu_x86_parse_featurestr(x86_def_t *x86_cpu_def, char *features)
> > > > >      x86_cpu_def->kvm_features &= ~minus_kvm_features;
> > > > >      x86_cpu_def->svm_features &= ~minus_svm_features;
> > > > >      x86_cpu_def->cpuid_7_0_ebx_features &= ~minus_7_0_ebx_features;
> > > > > +#ifdef CONFIG_KVM
> > > > >      if (check_cpuid && kvm_enabled()) {
> > > > >          if (kvm_check_features_against_host(x86_cpu_def) && enforce_cpuid)
> > > > >              goto error;
> > > > >      }
> > > > > +#endif
> > > > Provide kvm_check_features_against_host() stub if !CONFIG_KVM and drop
> > > > ifdef here.
> > > 
> > > I will do. Igor probably will have to change his "target-i386: move
> > > kvm_check_features_against_host() check to realize time" patch to use
> > > the same approach, too.
> > 
> > 
> > Gleb,
> > 
> > Why do stub here? As result we will be adding more ifdef-s just in other
> > places. Currently kvm_cpu_fill_host(), unavailable_host_feature() and
> Why will we be adding more ifdef-s in other places?
unavailable_host_feature() is being ifdef-ed above

> 
> > kvm_check_features_against_host() are bundled together in cpu.c so we could
> > instead ifdef whole block. Like here:
> > http://www.mail-archive.com/qemu-devel@nongnu.org/msg146536.html
> > 
> That's fine, but you can avoid things like:
> 
>      if (kvm_enabled() && name && strcmp(name, "host") == 0) {
> +#ifdef CONFIG_KVM
>          kvm_cpu_fill_host(x86_cpu_def);
> +#endif
> 
> in your patch by providing stub for kvm_cpu_fill_host() for !CONFIG_KVM
> case. This is common practice really. Avoid ifdefs in the code.
This ifdef could be eliminated later when cpus are converted into sub-classes.
Then we would put host subclass close to kvm_cpu_fill_host inside of the same
ifdef. that would leave ifdef around kvm_check_features_against_host() in
cpu_x86_parse_featurestr().

> 
> > For me code looks more readable with ifdef here, if we have stub, a reader
> > would have to look at kvm_check_features_against_host() body to see if it does
> > anything.
> > 
> If reader cares about kvm it has to anyway. If he does not, there is
> friendly kvm_enabled() (which is stub in case of !CONFIG_KVM BTW) to
> tell him that he does not care. No need additional ifdef there.

both ways would work, but if stubs are preferred style then there is no
point arguing.

> 
> --
> 			Gleb.

Patch

diff --git a/target-i386/cpu.c b/target-i386/cpu.c
index 1c3c7e1..876b0f6 100644
--- a/target-i386/cpu.c
+++ b/target-i386/cpu.c
@@ -936,6 +936,7 @@  static void kvm_cpu_fill_host(x86_def_t *x86_cpu_def)
 #endif /* CONFIG_KVM */
 }
 
+#ifdef CONFIG_KVM
 static int unavailable_host_feature(struct model_features_t *f, uint32_t mask)
 {
     int i;
@@ -987,6 +988,7 @@  static int kvm_check_features_against_host(x86_def_t *guest_def)
                 }
     return rv;
 }
+#endif
 
 static void x86_cpuid_version_get_family(Object *obj, Visitor *v, void *opaque,
                                          const char *name, Error **errp)
@@ -1410,10 +1412,12 @@  static int cpu_x86_parse_featurestr(x86_def_t *x86_cpu_def, char *features)
     x86_cpu_def->kvm_features &= ~minus_kvm_features;
     x86_cpu_def->svm_features &= ~minus_svm_features;
     x86_cpu_def->cpuid_7_0_ebx_features &= ~minus_7_0_ebx_features;
+#ifdef CONFIG_KVM
     if (check_cpuid && kvm_enabled()) {
         if (kvm_check_features_against_host(x86_cpu_def) && enforce_cpuid)
             goto error;
     }
+#endif
     return 0;
 
 error: