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>

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 7c26533..7017599 100644 (file)
--- 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;