[PATCH v3 6/8] KVM-HV: Add flush_on_enter before guest enter

["Nikunj A. Dadhania" <nikunj@linux.vnet.ibm.com>]

From: Nikunj A. Dadhania <nikunj@linux.vnet.ibm.com>

PV-Flush guest would indicate to flush on enter, flush the TLB before
entering and exiting the guest.

Signed-off-by: Nikunj A. Dadhania <nikunj@linux.vnet.ibm.com>
---
 arch/x86/kvm/x86.c |   23 +++++++----------------
 1 files changed, 7 insertions(+), 16 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 580abcf..a67e971 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1557,20 +1557,9 @@ static void record_steal_time(struct kvm_vcpu *vcpu)
 		&vcpu->arch.st.steal, sizeof(struct kvm_steal_time));
 }
 
-static void kvm_set_atomic(u64 *addr, u64 old, u64 new)
-{
-	int loop = 1000000;
-	while (1) {
-		if (cmpxchg(addr, old, new) == old)
-			break;
-		loop--;
-		if (!loop) {
-			pr_info("atomic cur: %lx old: %lx new: %lx\n",
-				*addr, old, new);
-			break;
-		}
-	}
-}
+#define VS_NOT_IN_GUEST      (0)
+#define VS_IN_GUEST          (1 << KVM_VCPU_STATE_IN_GUEST_MODE)
+#define VS_SHOULD_FLUSH      (1 << KVM_VCPU_STATE_SHOULD_FLUSH)
 
 static void kvm_set_vcpu_state(struct kvm_vcpu *vcpu)
 {
@@ -1584,7 +1573,8 @@ static void kvm_set_vcpu_state(struct kvm_vcpu *vcpu)
 	kaddr = kmap_atomic(vcpu->arch.v_state.vs_page);
 	kaddr += vcpu->arch.v_state.vs_offset;
 	vs = kaddr;
-	kvm_set_atomic(&vs->state, 0, 1 << KVM_VCPU_STATE_IN_GUEST_MODE);
+	if (xchg(&vs->state, VS_IN_GUEST) == VS_SHOULD_FLUSH)
+		kvm_x86_ops->tlb_flush(vcpu);
 	kunmap_atomic(kaddr);
 }
 
@@ -1600,7 +1590,8 @@ static void kvm_clear_vcpu_state(struct kvm_vcpu *vcpu)
 	kaddr = kmap_atomic(vcpu->arch.v_state.vs_page);
 	kaddr += vcpu->arch.v_state.vs_offset;
 	vs = kaddr;
-	kvm_set_atomic(&vs->state, 1 << KVM_VCPU_STATE_IN_GUEST_MODE, 0);
+	if (xchg(&vs->state, VS_NOT_IN_GUEST) == VS_SHOULD_FLUSH)
+		kvm_x86_ops->tlb_flush(vcpu);
 	kunmap_atomic(kaddr);
 }