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

[Eduardo Habkost <ehabkost@redhat.com>]

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(-)

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