[PATCH 22/21] kvm: x86: Only read/write MSR_KVM_ASYNC_PF_EN if supported

[Jan Kiszka <jan.kiszka@web.de>]

From: Jan Kiszka <jan.kiszka@siemens.com>

If the kernel does not support KVM_CAP_ASYNC_PF, it also does not know
about the related MSR. So skip it during state synchronization in that
case. Fixes annoying kernel warnings.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---
 target-i386/kvm.c |   12 ++++++++++--
 1 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/target-i386/kvm.c b/target-i386/kvm.c
index 79a1da8..af79526 100644
--- a/target-i386/kvm.c
+++ b/target-i386/kvm.c
@@ -64,6 +64,9 @@ const KVMCapabilityInfo kvm_arch_required_capabilities[] = {
 
 static bool has_msr_star;
 static bool has_msr_hsave_pa;
+#if defined(CONFIG_KVM_PARA) && defined(KVM_CAP_ASYNC_PF)
+static bool has_msr_async_pf_en;
+#endif
 static int lm_capable_kernel;
 
 static struct kvm_cpuid2 *try_get_cpuid(int max)
@@ -165,6 +168,7 @@ static int get_para_features(void)
             features |= (1 << para_features[i].feature);
         }
     }
+    has_msr_async_pf_en = features & (1 << KVM_FEATURE_ASYNC_PF);
     return features;
 }
 #endif
@@ -917,7 +921,9 @@ static int kvm_put_msrs(CPUState *env, int level)
                           env->system_time_msr);
         kvm_msr_entry_set(&msrs[n++], MSR_KVM_WALL_CLOCK, env->wall_clock_msr);
 #if defined(CONFIG_KVM_PARA) && defined(KVM_CAP_ASYNC_PF)
-        kvm_msr_entry_set(&msrs[n++], MSR_KVM_ASYNC_PF_EN, env->async_pf_en_msr);
+        if (has_msr_async_pf_en) {
+            kvm_msr_entry_set(&msrs[n++], MSR_KVM_ASYNC_PF_EN, env->async_pf_en_msr);
+        }
 #endif
     }
 #ifdef KVM_CAP_MCE
@@ -1149,7 +1155,9 @@ static int kvm_get_msrs(CPUState *env)
     msrs[n++].index = MSR_KVM_SYSTEM_TIME;
     msrs[n++].index = MSR_KVM_WALL_CLOCK;
 #if defined(CONFIG_KVM_PARA) && defined(KVM_CAP_ASYNC_PF)
-    msrs[n++].index = MSR_KVM_ASYNC_PF_EN;
+    if (has_msr_async_pf_en) {
+        msrs[n++].index = MSR_KVM_ASYNC_PF_EN;
+    }
 #endif
 
 #ifdef KVM_CAP_MCE