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[RFC,15/19] kvm: x86: Hook in kvmi_msr_event()

Message ID 20170616134348.17725-16-alazar@bitdefender.com (mailing list archive)
State New, archived
Headers show

Commit Message

Adalbert Lazăr June 16, 2017, 1:43 p.m. UTC 
From: Mihai Dontu <mdontu@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_EVENT_CONTROL(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 Dontu <mdontu@bitdefender.com>
---
 arch/x86/kvm/x86.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)
diff mbox

Patch

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 248fb7e99423..b7d2a9901665 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1090,6 +1090,23 @@  EXPORT_SYMBOL_GPL(kvm_enable_efer_bits);
  */
 int kvm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
 {
+	if (!msr->host_initiated) {
+		struct msr_data __msr;
+
+		memset(&__msr, 0, sizeof(__msr));
+		__msr.host_initiated = true;
+		__msr.index = msr->index;
+
+		if (!kvm_get_msr(vcpu, &__msr)) {
+			u64 data = msr->data;
+
+			if (kvmi_msr_event(vcpu, msr->index, __msr.data, &data))
+				msr->data = data;
+			else
+				return 0;
+		}
+	}
+
 	switch (msr->index) {
 	case MSR_FS_BASE:
 	case MSR_GS_BASE: