[PATCH V2 3/5] KVM/VMX: Add identical ept table pointer check

[Tianyu Lan <Tianyu.Lan@microsoft.com>]

This patch is to check ept table pointer of each cpus when set ept
tables and store identical ept table pointer if all ept table pointers
of single VM are same. This is for support of para-virt ept flush
hypercall.

Signed-off-by: Lan Tianyu <Tianyu.Lan@microsoft.com>
---
Change since v1:
       Replace identical_ept_pointer with ept_pointers_match and
check kvm_x86_ops->tlb_remote_flush in check_ept_pointer().
---
 arch/x86/kvm/vmx.c | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 1689f433f3a0..8142b2da430a 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -194,6 +194,9 @@ struct kvm_vmx {
 	unsigned int tss_addr;
 	bool ept_identity_pagetable_done;
 	gpa_t ept_identity_map_addr;
+
+	bool ept_pointers_match;
+	spinlock_t ept_pointer_lock;
 };
 
 #define NR_AUTOLOAD_MSRS 8
@@ -853,6 +856,7 @@ struct vcpu_vmx {
 	 */
 	u64 msr_ia32_feature_control;
 	u64 msr_ia32_feature_control_valid_bits;
+	u64 ept_pointer;
 };
 
 enum segment_cache_field {
@@ -4958,6 +4962,32 @@ static u64 construct_eptp(struct kvm_vcpu *vcpu, unsigned long root_hpa)
 	return eptp;
 }
 
+static void check_ept_pointer(struct kvm_vcpu *vcpu, u64 eptp)
+{
+	struct kvm *kvm = vcpu->kvm;
+	u64 tmp_eptp = INVALID_PAGE;
+	int i;
+
+	if (!kvm_x86_ops->tlb_remote_flush)
+		return;
+
+	spin_lock(&to_kvm_vmx(kvm)->ept_pointer_lock);
+	to_vmx(vcpu)->ept_pointer = eptp;
+
+	kvm_for_each_vcpu(i, vcpu, kvm) {
+		if (!VALID_PAGE(tmp_eptp)) {
+			tmp_eptp = to_vmx(vcpu)->ept_pointer;
+		} else if (tmp_eptp != to_vmx(vcpu)->ept_pointer) {
+			to_kvm_vmx(kvm)->ept_pointers_match = false;
+			spin_unlock(&to_kvm_vmx(kvm)->ept_pointer_lock);
+			return;
+		}
+	}
+
+	to_kvm_vmx(kvm)->ept_pointers_match = true;
+	spin_unlock(&to_kvm_vmx(kvm)->ept_pointer_lock);
+}
+
 static void vmx_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
 {
 	unsigned long guest_cr3;
@@ -4967,6 +4997,8 @@ static void vmx_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
 	if (enable_ept) {
 		eptp = construct_eptp(vcpu, cr3);
 		vmcs_write64(EPT_POINTER, eptp);
+		check_ept_pointer(vcpu, eptp);
+
 		if (enable_unrestricted_guest || is_paging(vcpu) ||
 		    is_guest_mode(vcpu))
 			guest_cr3 = kvm_read_cr3(vcpu);
@@ -10383,6 +10415,8 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id)
 
 static int vmx_vm_init(struct kvm *kvm)
 {
+	spin_lock_init(&to_kvm_vmx(kvm)->ept_pointer_lock);
+
 	if (!ple_gap)
 		kvm->arch.pause_in_guest = true;
 	return 0;
-- 
2.14.3