KVM: VMX: make PLE window per-VCPU

Change PLE window into per-VCPU variable, seeded from module parameter,
to allow greater flexibility.

Brings in a small overhead on every vmentry.

Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 11 insertions, 1 deletions

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 7c26533e149c..70175990536b 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -484,6 +484,10 @@ struct vcpu_vmx {
 
         /* Support for a guest hypervisor (nested VMX) */
         struct nested_vmx nested;
+
+        /* Dynamic PLE window. */
+        int ple_window;
+        bool ple_window_dirty;
 };
 
 enum segment_cache_field {
@@ -4402,7 +4406,8 @@ static int vmx_vcpu_setup(struct vcpu_vmx *vmx)
 
         if (ple_gap) {
                 vmcs_write32(PLE_GAP, ple_gap);
-                vmcs_write32(PLE_WINDOW, ple_window);
+                vmx->ple_window = ple_window;
+                vmx->ple_window_dirty = true;
         }
 
         vmcs_write32(PAGE_FAULT_ERROR_CODE_MASK, 0);
@@ -7389,6 +7394,11 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu)
         if (vmx->emulation_required)
                 return;
 
+        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);
                 vmx->nested.sync_shadow_vmcs = false;