Re: [PATCH v2 5/6] KVM: x86: Unconditionally set l1tf_flush_l1d during vCPU load

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On 22/05/2024 1:40 pm, Sean Christopherson wrote:
Always set l1tf_flush_l1d during kvm_arch_vcpu_load() instead of setting
it only when the vCPU is being scheduled back in.  The flag is processed
only when VM-Enter is imminent, and KVM obviously needs to load the vCPU
before VM-Enter, so attempting to precisely set l1tf_flush_l1d provides no
meaningful value.  I.e. the flag _will_ be set either way, it's simply a
matter of when.

Seems reasonable.


Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---

Acked-by: Kai Huang <kai.huang@xxxxxxxxx>

  arch/x86/kvm/x86.c | 11 +++++------
  1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 59aa772af755..60fea297f91f 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5006,12 +5006,11 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
  {
  	struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
- if (vcpu->scheduled_out) {
-		vcpu->arch.l1tf_flush_l1d = true;
-		if (pmu->version && unlikely(pmu->event_count)) {
-			pmu->need_cleanup = true;
-			kvm_make_request(KVM_REQ_PMU, vcpu);
-		}
+	vcpu->arch.l1tf_flush_l1d = true;
+
+	if (vcpu->scheduled_out && pmu->version && pmu->event_count) {
+		pmu->need_cleanup = true;
+		kvm_make_request(KVM_REQ_PMU, vcpu);
  	}

Nit, the unlikely() is lost, but I guess it is OK?




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