linux-kernel - [PATCH 3/9] KVM: VMX: make PLE window per-vcpu

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Date:	Tue, 19 Aug 2014 22:35:30 +0200
From:	Radim Krčmář <rkrcmar@...hat.com>
To:	kvm@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
	Gleb Natapov <gleb@...nel.org>,
	Raghavendra KT <raghavendra.kt@...ux.vnet.ibm.com>,
	Vinod Chegu <chegu_vinod@...com>, Hui-Zhi <hui-zhi.zhao@...com>
Subject: [PATCH 3/9] 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@...hat.com>
---
 I've been thinking about a general hierarchical per-vcpu variable model,
 but it's hard to have current performance and sane code.

 arch/x86/kvm/vmx.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 2b306f9..eaa5574 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -484,6 +484,9 @@ struct vcpu_vmx {
 
 	/* Support for a guest hypervisor (nested VMX) */
 	struct nested_vmx nested;
+
+	/* Dynamic PLE window. */
+	int ple_window;
 };
 
 enum segment_cache_field {
@@ -4403,6 +4406,7 @@ 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;
 	}
 
 	vmcs_write32(PAGE_FAULT_ERROR_CODE_MASK, 0);
@@ -7387,6 +7391,9 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu)
 	if (vmx->emulation_required)
 		return;
 
+	if (ple_gap)
+		vmcs_write32(PLE_WINDOW, vmx->ple_window);
+
 	if (vmx->nested.sync_shadow_vmcs) {
 		copy_vmcs12_to_shadow(vmx);
 		vmx->nested.sync_shadow_vmcs = false;
-- 
2.0.4

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