[RFC PATCH v4 14/18] kvm: x86: hook in kvmi_cr_event()

[Adalber Lazăr <alazar@xxxxxxxxxxxxxxx>]

From: Adalbert Lazar <alazar@xxxxxxxxxxxxxxx>

Notify the guest introspection tool that cr{0,3,4} is going to be
changed. The function kvmi_cr_event() will load in crX the new value
if the tool permits it.

Signed-off-by: Mihai Donțu <mdontu@xxxxxxxxxxxxxxx>
---
 arch/x86/kvm/x86.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index caf50b7307a4..8f5cc81c8760 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -676,6 +676,9 @@ int kvm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
 	if (!(cr0 & X86_CR0_PG) && kvm_read_cr4_bits(vcpu, X86_CR4_PCIDE))
 		return 1;
 
+	if (!kvmi_cr_event(vcpu, 0, old_cr0, &cr0))
+		return 1;
+
 	kvm_x86_ops->set_cr0(vcpu, cr0);
 
 	if ((cr0 ^ old_cr0) & X86_CR0_PG) {
@@ -816,6 +819,9 @@ int kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
 			return 1;
 	}
 
+	if (!kvmi_cr_event(vcpu, 4, old_cr4, &cr4))
+		return 1;
+
 	if (kvm_x86_ops->set_cr4(vcpu, cr4))
 		return 1;
 
@@ -832,11 +838,13 @@ EXPORT_SYMBOL_GPL(kvm_set_cr4);
 
 int kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
 {
+	unsigned long old_cr3 = kvm_read_cr3(vcpu);
+
 #ifdef CONFIG_X86_64
 	cr3 &= ~CR3_PCID_INVD;
 #endif
 
-	if (cr3 == kvm_read_cr3(vcpu) && !pdptrs_changed(vcpu)) {
+	if (cr3 == old_cr3 && !pdptrs_changed(vcpu)) {
 		kvm_mmu_sync_roots(vcpu);
 		kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu);
 		return 0;
@@ -849,6 +857,9 @@ int kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
 		   !load_pdptrs(vcpu, vcpu->arch.walk_mmu, cr3))
 		return 1;
 
+	if (!kvmi_cr_event(vcpu, 3, old_cr3, &cr3))
+		return 1;
+
 	vcpu->arch.cr3 = cr3;
 	__set_bit(VCPU_EXREG_CR3, (ulong *)&vcpu->arch.regs_avail);
 	kvm_mmu_new_cr3(vcpu);