[PATCH v3 7/7] KVM: VMX: optimize ple_window updates to VMCS

[Radim Krčmář]

ple_window is preserved in VMCS, so can write it only after a change.
Do this by keeping a dirty bit.

Signed-off-by: Radim Krčmář <rkrc...@redhat.com>
---
 arch/x86/kvm/vmx.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 1318232..f32415b 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -510,6 +510,7 @@ struct vcpu_vmx {
 
        /* Dynamic PLE window. */
        int ple_window;
+       bool ple_window_dirty;
 };
 
 enum segment_cache_field {
@@ -4426,6 +4427,7 @@ static int vmx_vcpu_setup(struct vcpu_vmx *vmx)
                vmcs_write64(POSTED_INTR_DESC_ADDR, __pa((&vmx->pi_desc)));
        }
 
+       vmx->ple_window_dirty = ple_gap;
        if (ple_gap) {
                vmcs_write32(PLE_GAP, ple_gap);
                vmx->ple_window = ple_window;
@@ -5741,6 +5743,9 @@ static void grow_ple_window(struct kvm_vcpu *vcpu)
                vmx->ple_window = __grow_ple_window(old);
        } while (read_seqretry(&ple_window_seqlock, seq));
 
+       if (vmx->ple_window != old)
+               vmx->ple_window_dirty = true;
+
        trace_kvm_ple_window_grow(vcpu->vcpu_id, vmx->ple_window, old);
 }
 
@@ -5756,6 +5761,9 @@ static void shrink_ple_window(struct kvm_vcpu *vcpu)
                                                      ple_window);
        } while (read_seqretry(&ple_window_seqlock, seq));
 
+       if (vmx->ple_window != old)
+               vmx->ple_window_dirty = true;
+
        trace_kvm_ple_window_shrink(vcpu->vcpu_id, vmx->ple_window, old);
 }
 
@@ -7505,8 +7513,10 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu)
        if (vmx->emulation_required)
                return;
 
-       if (ple_gap)
+       if (vmx->ple_window_dirty) {
+               vmx->ple_window_dirty = false;
                vmcs_write32(PLE_WINDOW, vmx->ple_window);
+       }
 
        if (vmx->nested.sync_shadow_vmcs) {
                copy_vmcs12_to_shadow(vmx);
-- 
2.1.0

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