[PATCH 8/9] KVM: VMX: runtime knobs for dynamic PLE window

["Radim Krčmář" <rkrcmar@redhat.com>]

ple_window is updated on every vmentry, so there is no reason to have it
read-only anymore.
ple_window_* weren't writable to prevent runtime overflow races;
they are mitigated by clamping the value of ple_window.

Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
---
 If we decide to ignore insane overflows, last two hunks can be dropped.

 arch/x86/kvm/vmx.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index c6cfb71..d7f58e8 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -134,19 +134,19 @@ static int ple_gap = KVM_VMX_DEFAULT_PLE_GAP;
 module_param(ple_gap, int, S_IRUGO);
 
 static int ple_window = KVM_VMX_DEFAULT_PLE_WINDOW;
-module_param(ple_window, int, S_IRUGO);
+module_param(ple_window, int, S_IRUGO | S_IWUSR);
 
 /* Default doubles per-vcpu window every exit. */
 static int ple_window_grow = KVM_VMX_DEFAULT_PLE_WINDOW_GROW;
-module_param(ple_window_grow, int, S_IRUGO);
+module_param(ple_window_grow, int, S_IRUGO | S_IWUSR);
 
 /* Default resets per-vcpu window every exit to ple_window. */
 static int ple_window_shrink = KVM_VMX_DEFAULT_PLE_WINDOW_SHRINK;
-module_param(ple_window_shrink, int, S_IRUGO);
+module_param(ple_window_shrink, int, S_IRUGO | S_IWUSR);
 
 /* Default is to compute the maximum so we can never overflow. */
 static int ple_window_max = INT_MAX / KVM_VMX_DEFAULT_PLE_WINDOW_GROW;
-module_param(ple_window_max, int, S_IRUGO);
+module_param(ple_window_max, int, S_IRUGO | S_IWUSR);
 
 extern const ulong vmx_return;
 
@@ -5694,7 +5694,8 @@ static int handle_invalid_guest_state(struct kvm_vcpu *vcpu)
 out:
 	return ret;
 }
-#define make_ple_window_modifier(type, oplt, opge, cmp, bound) \
+
+#define make_ple_window_modifier(type, oplt, opge) \
 static void type##_ple_window(struct kvm_vcpu *vcpu) \
 { \
 	struct vcpu_vmx *vmx = to_vmx(vcpu); \
@@ -5708,13 +5709,13 @@ static void type##_ple_window(struct kvm_vcpu *vcpu) \
 	else \
 		new = old opge ple_window_##type; \
 \
-	vmx->ple_window = cmp(new, bound); \
+	vmx->ple_window = clamp(new, ple_window, ple_window_max); \
 \
 	trace_kvm_ple_window_##type(vcpu->vcpu_id, vmx->ple_window, old); \
 }
 
-make_ple_window_modifier(grow,   *, +, min, ple_window_max)
-make_ple_window_modifier(shrink, /, -, max, ple_window)
+make_ple_window_modifier(grow,   *, +) /* grow_ple_window */
+make_ple_window_modifier(shrink, /, -) /* shrink_ple_window */
 
 /*
  * Indicate a busy-waiting vcpu in spinlock. We do not enable the PAUSE
-- 
2.0.4