[Qemu-devel] [PATCH-for-4.2 1/1] Only enable the halt poll control MSR if it is supported by the host

[Mark Kanda <mark.kanda@oracle.com>]

The halt poll control MSR should only be enabled on hosts which
support it.

Fixes: ("kvm: i386: halt poll control MSR support")

Signed-off-by: Mark Kanda <mark.kanda@oracle.com>
---
 target/i386/cpu.c     | 8 +++++++-
 target/i386/kvm.c     | 2 --
 target/i386/machine.c | 1 -
 3 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index a8bafdb8b9..dacbf7a9fe 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -2838,7 +2838,6 @@ static PropValue kvm_default_props[] = {
     { "kvm-asyncpf", "on" },
     { "kvm-steal-time", "on" },
     { "kvm-pv-eoi", "on" },
-    { "kvm-poll-control", "on" },
     { "kvmclock-stable-bit", "on" },
     { "x2apic", "on" },
     { "acpi", "off" },
@@ -5109,6 +5108,13 @@ static void x86_cpu_expand_features(X86CPU *cpu, Error **errp)
         env->cpuid_xlevel2 = env->cpuid_min_xlevel2;
     }
 
+    /* Enable the halt poll control MSR if it is supported by the host */
+    if (x86_cpu_get_supported_feature_word(FEAT_KVM, cpu->migratable) &
+        (1 << KVM_FEATURE_POLL_CONTROL)) {
+        env->features[FEAT_KVM] |= 1 << KVM_FEATURE_POLL_CONTROL;
+        env->poll_control_msr = 1;
+    }
+
 out:
     if (local_err != NULL) {
         error_propagate(errp, local_err);
diff --git a/target/i386/kvm.c b/target/i386/kvm.c
index cb22684139..81dd5d2c1b 100644
--- a/target/i386/kvm.c
+++ b/target/i386/kvm.c
@@ -1796,8 +1796,6 @@ void kvm_arch_reset_vcpu(X86CPU *cpu)
 
         hyperv_x86_synic_reset(cpu);
     }
-    /* enabled by default */
-    env->poll_control_msr = 1;
 }
 
 void kvm_arch_do_init_vcpu(X86CPU *cpu)
diff --git a/target/i386/machine.c b/target/i386/machine.c
index 20077a8a5a..9d6095b264 100644
--- a/target/i386/machine.c
+++ b/target/i386/machine.c
@@ -394,7 +394,6 @@ static bool steal_time_msr_needed(void *opaque)
     return cpu->env.steal_time_msr != 0;
 }
 
-/* Poll control MSR enabled by default */
 static bool poll_control_msr_needed(void *opaque)
 {
     X86CPU *cpu = opaque;
-- 
2.21.0