Patchwork [1/2] target-i386: Don't set any KVM flag by default if KVM is disabled

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Submitter Eduardo Habkost
Date Jan. 4, 2013, 2:52 p.m.
Message ID <1357311145-16410-2-git-send-email-ehabkost@redhat.com>
Download mbox | patch
Permalink /patch/209474/
State New
Headers show

Comments

Eduardo Habkost - Jan. 4, 2013, 2:52 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
CONFIG_KVM and 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>
---
 target-i386/cpu.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)
Blue Swirl - Jan. 4, 2013, 8:47 p.m.
On Fri, Jan 4, 2013 at 2:52 PM, 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
> CONFIG_KVM and 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>
> ---
>  target-i386/cpu.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/target-i386/cpu.c b/target-i386/cpu.c
> index 82685dc..808001a 100644
> --- a/target-i386/cpu.c
> +++ b/target-i386/cpu.c
> @@ -145,15 +145,16 @@ static uint32_t kvm_default_features = (1 << KVM_FEATURE_CLOCKSOURCE) |
>          (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;
> +#ifdef CONFIG_KVM
> +    if (kvm_enabled())

Missing braces, please read CODING_STYLE and use checkpatch.pl to find
problems in patches.

> +        kvm_default_features |= (1UL << KVM_FEATURE_PV_EOI);
> +#endif
>  }
>
>  void host_cpuid(uint32_t function, uint32_t count,
> --
> 1.7.11.7
>
>
Eduardo Habkost - Jan. 4, 2013, 9:02 p.m.
On Fri, Jan 04, 2013 at 08:47:07PM +0000, Blue Swirl wrote:
> >  {
> > -    kvm_default_features |= kvm_pv_eoi_features;
> > +#ifdef CONFIG_KVM
> > +    if (kvm_enabled())
> 
> Missing braces, please read CODING_STYLE and use checkpatch.pl to find
> problems in patches.

Sorry (again). I will soon send a new version fixing the coding style
problems.
Eduardo Habkost - Jan. 4, 2013, 9:25 p.m.
On Fri, Jan 04, 2013 at 07:02:17PM -0200, Eduardo Habkost wrote:
> On Fri, Jan 04, 2013 at 08:47:07PM +0000, Blue Swirl wrote:
> > >  {
> > > -    kvm_default_features |= kvm_pv_eoi_features;
> > > +#ifdef CONFIG_KVM
> > > +    if (kvm_enabled())
> > 
> > Missing braces, please read CODING_STYLE and use checkpatch.pl to find
> > problems in patches.
> 
> Sorry (again). I will soon send a new version fixing the coding style
> problems.

checkpatch.pl is behaving weirdly, here:

$ git show 193e2f6 | grep 'if (kvm'
+    if (kvm_enabled())
$ git show 193e2f6 | ./scripts/checkpatch.pl -
total: 0 errors, 0 warnings, 19 lines checked

Your patch has no obvious style problems and is ready for submission.
$

Patch

diff --git a/target-i386/cpu.c b/target-i386/cpu.c
index 82685dc..808001a 100644
--- a/target-i386/cpu.c
+++ b/target-i386/cpu.c
@@ -145,15 +145,16 @@  static uint32_t kvm_default_features = (1 << KVM_FEATURE_CLOCKSOURCE) |
         (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;
+#ifdef CONFIG_KVM
+    if (kvm_enabled())
+        kvm_default_features |= (1UL << KVM_FEATURE_PV_EOI);
+#endif
 }
 
 void host_cpuid(uint32_t function, uint32_t count,