Patchwork [RFC,02/12] target-i386: Don't set any KVM flag by default if KVM is disabled

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Submitter Eduardo Habkost
Date Jan. 9, 2013, 6:53 p.m.
Message ID <1357757632-1950-3-git-send-email-ehabkost@redhat.com>
Download mbox | patch
Permalink /patch/210822/
State New
Headers show

Comments

Eduardo Habkost - Jan. 9, 2013, 6:53 p.m.
This is a cleanup that tries to solve two small issues:

 - We don't need a separate kvm_pv_eoi_features variable just to keep a
   constant calculated at compile-time, and this style would require
   adding a separate variable (that's declared twice because of the
   CONFIG_KVM ifdef) for each feature that's going to be enabled/disable
   by machine-type compat code.
 - The pc-1.3 code is setting the kvm_pv_eoi flag on cpuid_kvm_features
   even when KVM is disabled at runtime. This small incosistency in
   the cpuid_kvm_features field isn't a problem today because
   cpuid_kvm_features is ignored by the TCG code, but it may cause
   unexpected problems later when refactoring the CPUID handling code.

This patch eliminates the kvm_pv_eoi_features variable and simply uses
kvm_enabled() inside the enable_kvm_pv_eoi() compat function, so it
enables kvm_pv_eoi only if KVM is enabled. I believe this makes the
behavior of enable_kvm_pv_eoi() clearer and easier to understand.

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
---
Cc: kvm@vger.kernel.org
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Gleb Natapov <gleb@redhat.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>

Changes v2:
 - Coding style fix

Changes v3:
 - Eliminate #ifdef by using the fake KVM_FEATURE_PV_EOI #define

Changes v4:
 - Check kvm_enabled() when actually using kvm_default_features
 - Eliminate Yet Another #ifdef by using the fake KVM_FEATURE_*
   #defines on kvm_default_features initialization
---
 target-i386/cpu.c | 16 ++++++----------
 1 file changed, 6 insertions(+), 10 deletions(-)
Michael S. Tsirkin - Jan. 10, 2013, 11:47 a.m.
On Wed, Jan 09, 2013 at 04:53:42PM -0200, Eduardo Habkost wrote:
> This is a cleanup that tries to solve two small issues:
> 
>  - We don't need a separate kvm_pv_eoi_features variable just to keep a
>    constant calculated at compile-time, and this style would require
>    adding a separate variable (that's declared twice because of the
>    CONFIG_KVM ifdef) for each feature that's going to be enabled/disable
>    by machine-type compat code.
>  - The pc-1.3 code is setting the kvm_pv_eoi flag on cpuid_kvm_features
>    even when KVM is disabled at runtime. This small incosistency in
>    the cpuid_kvm_features field isn't a problem today because
>    cpuid_kvm_features is ignored by the TCG code, but it may cause
>    unexpected problems later when refactoring the CPUID handling code.
> 
> This patch eliminates the kvm_pv_eoi_features variable and simply uses
> kvm_enabled() inside the enable_kvm_pv_eoi() compat function, so it
> enables kvm_pv_eoi only if KVM is enabled. I believe this makes the
> behavior of enable_kvm_pv_eoi() clearer and easier to understand.
> 
> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>

Acked-by: Michael S. Tsirkin <mst@redhat.com>



> ---
> Cc: kvm@vger.kernel.org
> Cc: Michael S. Tsirkin <mst@redhat.com>
> Cc: Gleb Natapov <gleb@redhat.com>
> Cc: Marcelo Tosatti <mtosatti@redhat.com>
> 
> Changes v2:
>  - Coding style fix
> 
> Changes v3:
>  - Eliminate #ifdef by using the fake KVM_FEATURE_PV_EOI #define
> 
> Changes v4:
>  - Check kvm_enabled() when actually using kvm_default_features
>  - Eliminate Yet Another #ifdef by using the fake KVM_FEATURE_*
>    #defines on kvm_default_features initialization
> ---
>  target-i386/cpu.c | 16 ++++++----------
>  1 file changed, 6 insertions(+), 10 deletions(-)
> 
> diff --git a/target-i386/cpu.c b/target-i386/cpu.c
> index e4dc370..57a22b7 100644
> --- a/target-i386/cpu.c
> +++ b/target-i386/cpu.c
> @@ -206,22 +206,16 @@ typedef struct model_features_t {
>  int check_cpuid = 0;
>  int enforce_cpuid = 0;
>  
> -#if defined(CONFIG_KVM)
>  static uint32_t kvm_default_features = (1 << KVM_FEATURE_CLOCKSOURCE) |
>          (1 << KVM_FEATURE_NOP_IO_DELAY) |
>          (1 << KVM_FEATURE_CLOCKSOURCE2) |
>          (1 << KVM_FEATURE_ASYNC_PF) |
>          (1 << KVM_FEATURE_STEAL_TIME) |
>          (1 << KVM_FEATURE_CLOCKSOURCE_STABLE_BIT);
> -static const uint32_t kvm_pv_eoi_features = (0x1 << KVM_FEATURE_PV_EOI);
> -#else
> -static uint32_t kvm_default_features = 0;
> -static const uint32_t kvm_pv_eoi_features = 0;
> -#endif
>  
>  void enable_kvm_pv_eoi(void)
>  {
> -    kvm_default_features |= kvm_pv_eoi_features;
> +    kvm_default_features |= (1UL << KVM_FEATURE_PV_EOI);
>  }
>  
>  void host_cpuid(uint32_t function, uint32_t count,
> @@ -1343,13 +1337,15 @@ static int cpu_x86_parse_featurestr(x86_def_t *x86_cpu_def, char *features)
>      unsigned int i;
>      char *featurestr; /* Single 'key=value" string being parsed */
>      /* Features to be added */
> -    FeatureWordArray plus_features = {
> -        [FEAT_KVM] = kvm_default_features,
> -    };
> +    FeatureWordArray plus_features = { 0 };
>      /* Features to be removed */
>      FeatureWordArray minus_features = { 0 };
>      uint32_t numvalue;
>  
> +    if (kvm_enabled()) {
> +        plus_features[FEAT_KVM] = kvm_default_features;
> +    }
> +
>      add_flagname_to_bitmaps("hypervisor", plus_features);
>  
>      featurestr = features ? strtok(features, ",") : NULL;
> -- 
> 1.7.11.7
Igor Mammedov - Jan. 10, 2013, 11:07 p.m.
On Wed,  9 Jan 2013 16:53:42 -0200
Eduardo Habkost <ehabkost@redhat.com> wrote:

> This is a cleanup that tries to solve two small issues:
> 
>  - We don't need a separate kvm_pv_eoi_features variable just to keep a
>    constant calculated at compile-time, and this style would require
>    adding a separate variable (that's declared twice because of the
>    CONFIG_KVM ifdef) for each feature that's going to be enabled/disable
>    by machine-type compat code.
>  - The pc-1.3 code is setting the kvm_pv_eoi flag on cpuid_kvm_features
>    even when KVM is disabled at runtime. This small incosistency in
>    the cpuid_kvm_features field isn't a problem today because
>    cpuid_kvm_features is ignored by the TCG code, but it may cause
>    unexpected problems later when refactoring the CPUID handling code.
> 
> This patch eliminates the kvm_pv_eoi_features variable and simply uses
> kvm_enabled() inside the enable_kvm_pv_eoi() compat function, so it
> enables kvm_pv_eoi only if KVM is enabled. I believe this makes the
> behavior of enable_kvm_pv_eoi() clearer and easier to understand.
> 
> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> ---
> Cc: kvm@vger.kernel.org
> Cc: Michael S. Tsirkin <mst@redhat.com>
> Cc: Gleb Natapov <gleb@redhat.com>
> Cc: Marcelo Tosatti <mtosatti@redhat.com>
> 
[snip]
>  void host_cpuid(uint32_t function, uint32_t count,
> @@ -1343,13 +1337,15 @@ static int cpu_x86_parse_featurestr(x86_def_t *x86_cpu_def, char *features)
>      unsigned int i;
>      char *featurestr; /* Single 'key=value" string being parsed */
>      /* Features to be added */
> -    FeatureWordArray plus_features = {
> -        [FEAT_KVM] = kvm_default_features,
> -    };
> +    FeatureWordArray plus_features = { 0 };
>      /* Features to be removed */
>      FeatureWordArray minus_features = { 0 };
>      uint32_t numvalue;
>  
> +    if (kvm_enabled()) {
> +        plus_features[FEAT_KVM] = kvm_default_features;
> +    }
While touching it please move setting defaults to cpu_x86_register() or
cpu_x86_find_by_name() to so that cpu_x86_parse_featurestr() would deal only
with custom settings.

[snip]
Eduardo Habkost - Jan. 11, 2013, 12:03 a.m.
On Fri, Jan 11, 2013 at 12:07:40AM +0100, Igor Mammedov wrote:
[...]
> > @@ -1343,13 +1337,15 @@ static int cpu_x86_parse_featurestr(x86_def_t *x86_cpu_def, char *features)
> >      unsigned int i;
> >      char *featurestr; /* Single 'key=value" string being parsed */
> >      /* Features to be added */
> > -    FeatureWordArray plus_features = {
> > -        [FEAT_KVM] = kvm_default_features,
> > -    };
> > +    FeatureWordArray plus_features = { 0 };
> >      /* Features to be removed */
> >      FeatureWordArray minus_features = { 0 };
> >      uint32_t numvalue;
> >  
> > +    if (kvm_enabled()) {
> > +        plus_features[FEAT_KVM] = kvm_default_features;
> > +    }
> While touching it please move setting defaults to cpu_x86_register() or
> cpu_x86_find_by_name() to so that cpu_x86_parse_featurestr() would deal only
> with custom settings.

OK, I will do it in the next version.

Patch

diff --git a/target-i386/cpu.c b/target-i386/cpu.c
index e4dc370..57a22b7 100644
--- a/target-i386/cpu.c
+++ b/target-i386/cpu.c
@@ -206,22 +206,16 @@  typedef struct model_features_t {
 int check_cpuid = 0;
 int enforce_cpuid = 0;
 
-#if defined(CONFIG_KVM)
 static uint32_t kvm_default_features = (1 << KVM_FEATURE_CLOCKSOURCE) |
         (1 << KVM_FEATURE_NOP_IO_DELAY) |
         (1 << KVM_FEATURE_CLOCKSOURCE2) |
         (1 << KVM_FEATURE_ASYNC_PF) |
         (1 << KVM_FEATURE_STEAL_TIME) |
         (1 << KVM_FEATURE_CLOCKSOURCE_STABLE_BIT);
-static const uint32_t kvm_pv_eoi_features = (0x1 << KVM_FEATURE_PV_EOI);
-#else
-static uint32_t kvm_default_features = 0;
-static const uint32_t kvm_pv_eoi_features = 0;
-#endif
 
 void enable_kvm_pv_eoi(void)
 {
-    kvm_default_features |= kvm_pv_eoi_features;
+    kvm_default_features |= (1UL << KVM_FEATURE_PV_EOI);
 }
 
 void host_cpuid(uint32_t function, uint32_t count,
@@ -1343,13 +1337,15 @@  static int cpu_x86_parse_featurestr(x86_def_t *x86_cpu_def, char *features)
     unsigned int i;
     char *featurestr; /* Single 'key=value" string being parsed */
     /* Features to be added */
-    FeatureWordArray plus_features = {
-        [FEAT_KVM] = kvm_default_features,
-    };
+    FeatureWordArray plus_features = { 0 };
     /* Features to be removed */
     FeatureWordArray minus_features = { 0 };
     uint32_t numvalue;
 
+    if (kvm_enabled()) {
+        plus_features[FEAT_KVM] = kvm_default_features;
+    }
+
     add_flagname_to_bitmaps("hypervisor", plus_features);
 
     featurestr = features ? strtok(features, ",") : NULL;