KVM: x86: Drop now-superflous setting of l1tf_flush_l1d in vcpu_run()

Now that KVM unconditionally sets l1tf_flush_l1d in kvm_arch_vcpu_load(),
drop the redundant store from vcpu_run().  The flag is cleared only when
VM-Enter is imminent, deep below vcpu_run(), i.e. barring a KVM bug, it's
impossible for l1tf_flush_l1d to be cleared between loading the vCPU and
calling vcpu_run().
Acked-by: Kai Huang <kai.huang@intel.com>
Link: https://lore.kernel.org/r/20240522014013.1672962-7-seanjc@google.comSigned-off-by: Sean Christopherson <seanjc@google.com>

arch/x86/kvm/vmx/vmx.c

@@ -6673,9 +6673,10 @@ static noinstr void vmx_l1d_flush(struct kvm_vcpu *vcpu)
 		bool flush_l1d;
 
 		/*
-		 * Clear the per-vcpu flush bit, it gets set again
-		 * either from vcpu_run() or from one of the unsafe
-		 * VMEXIT handlers.
+		 * Clear the per-vcpu flush bit, it gets set again if the vCPU
+		 * is reloaded, i.e. if the vCPU is scheduled out or if KVM
+		 * exits to userspace, or if KVM reaches one of the unsafe
+		 * VMEXIT handlers, e.g. if KVM calls into the emulator.
 		 */
 		flush_l1d = vcpu->arch.l1tf_flush_l1d;
 		vcpu->arch.l1tf_flush_l1d = false;

arch/x86/kvm/x86.c

@@ -11253,7 +11253,6 @@ static int vcpu_run(struct kvm_vcpu *vcpu)
 	int r;
 
 	vcpu->run->exit_reason = KVM_EXIT_UNKNOWN;
-	vcpu->arch.l1tf_flush_l1d = true;
 
 	for (;;) {
 		/*