[PATCH v2 6/6] KVM: x86: Drop now-superflous setting of l1tf_flush_l1d in vcpu_run()

From: Sean Christopherson
Date: Tue May 21 2024 - 21:42:24 EST


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().

Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
arch/x86/kvm/vmx/vmx.c | 7 ++++---
arch/x86/kvm/x86.c | 1 -
2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index da2f95385a12..552b6a9887a5 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6672,9 +6672,10 @@ 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;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 60fea297f91f..86ae7392cc59 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -11264,7 +11264,6 @@ static int vcpu_run(struct kvm_vcpu *vcpu)
int r;

vcpu->run->exit_reason = KVM_EXIT_UNKNOWN;
- vcpu->arch.l1tf_flush_l1d = true;

for (;;) {
/*
--
2.45.0.215.g3402c0e53f-goog