[RFC PATCH v4 16/18] kvm: x86: hook in kvmi_msr_event()

["Adalber Lazăr" <alazar@bitdefender.com>]

From: Adalbert Lazar <alazar@bitdefender.com>

Inform the guest introspection tool that an MSR is going to be changed.

The kvmi_msr_event() function will check a bitmap of MSR-s of interest
(configured via a KVMI_CONTROL_EVENTS(KVMI_MSR_CONTROL) request) and, if
the new value differs from the previous one, it will generate a
notification. The introspection tool can respond by allowing the guest
to continue with normal execution or by discarding the change.

This is meant to prevent malicious changes to MSR-s such as
MSR_IA32_SYSENTER_EIP.

Signed-off-by: Mihai DonE?u <mdontu@bitdefender.com>
---
 arch/x86/kvm/x86.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 284bb4c740fa..271028ccbeca 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1111,6 +1111,9 @@ EXPORT_SYMBOL_GPL(kvm_enable_efer_bits);
  */
 int kvm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
 {
+	if (!kvmi_msr_event(vcpu, msr))
+		return 1;
+
 	switch (msr->index) {
 	case MSR_FS_BASE:
 	case MSR_GS_BASE:

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