x86: kvm_hv_set_msr(): use __put_user() instead of 32bit __clear_user()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

arch/x86/kvm/hyperv.c

@@ -1129,7 +1129,7 @@ static int kvm_hv_set_msr(struct kvm_vcpu *vcpu, u32 msr, u64 data, bool host)
 		 * only, there can be valuable data in the rest which needs
 		 * to be preserved e.g. on migration.
 		 */
-		if (__clear_user((void __user *)addr, sizeof(u32)))
+		if (__put_user(0, (u32 __user *)addr))
 			return 1;
 		hv_vcpu->hv_vapic = data;
 		kvm_vcpu_mark_page_dirty(vcpu, gfn);