[MODERATED] [RFC PATCH 3/6] kvm: handle host mode irqs 3

[Nicolai Stange <nstange@suse.de>]

Currently, vmx_vcpu_run() checks if ->l1tf_flush_l1d is set and invokes
vmx_l1d_flush() if so.

This test is unncessary for the "always flush L1d" mode.

Move the check to vmx_l1d_flush()'s conditional mode code path.

Notes:
- vmx_l1d_flush() is likely to get inlined anyway and thus, there's no
  extra function call.
- This change inverts the (static) branch prediction, but there hadn't been
  any explicit likely()/unlikely() annotations before and so I decided
  to leave it as is.

Signed-off-by: Nicolai Stange <nstange@suse.de>
---
 arch/x86/kvm/vmx.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 5139738cc5a9..ec955b870756 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -9693,12 +9693,16 @@ static void vmx_l1d_flush(struct kvm_vcpu *vcpu)
 	 * 'always'
 	 */
 	if (static_branch_likely(&vmx_l1d_flush_cond)) {
+		bool flush_l1d = vcpu->arch.l1tf_flush_l1d;
+
 		/*
 		 * Clear the flush bit, it gets set again either from
 		 * vcpu_run() or from one of the unsafe VMEXIT
 		 * handlers.
 		 */
 		vcpu->arch.l1tf_flush_l1d = false;
+		if (!flush_l1d)
+			return;
 	}
 
 	vcpu->stat.l1d_flush++;
@@ -10228,10 +10232,8 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu)
 	evmcs_rsp = static_branch_unlikely(&enable_evmcs) ?
 		(unsigned long)&current_evmcs->host_rsp : 0;
 
-	if (static_branch_unlikely(&vmx_l1d_should_flush)) {
-		if (vcpu->arch.l1tf_flush_l1d)
-			vmx_l1d_flush(vcpu);
-	}
+	if (static_branch_unlikely(&vmx_l1d_should_flush))
+		vmx_l1d_flush(vcpu);
 
 	asm(
 		/* Store host registers */
-- 
2.13.7