From: Nicușor Cîțu <nicu.c...@icloud.com>
This commit also ensures that the introspection tool and the userspace
do not disable each other the MSR access VM-exit.
Signed-off-by: Nicușor Cîțu <nicu.c...@icloud.com>
Signed-off-by: Adalbert Lazăr <ala...@bitdefender.com>
---
arch/x86/include/asm/kvmi_host.h | 12 +++
arch/x86/kvm/kvmi.c | 124 +++++++++++++++++++++++++++----
arch/x86/kvm/svm/svm.c | 10 +++
arch/x86/kvm/vmx/vmx.c | 11 +++
4 files changed, 142 insertions(+), 15 deletions(-)
diff --git a/arch/x86/include/asm/kvmi_host.h b/arch/x86/include/asm/kvmi_host.h
index 5a4fc5b80907..8822f0310156 100644
--- a/arch/x86/include/asm/kvmi_host.h
+++ b/arch/x86/include/asm/kvmi_host.h
@@ -26,6 +26,12 @@ struct kvmi_interception {
DECLARE_BITMAP(low, KVMI_NUM_MSR);
DECLARE_BITMAP(high, KVMI_NUM_MSR);
} kvmi_mask;
+ struct {
+ DECLARE_BITMAP(low, KVMI_NUM_MSR);
+ DECLARE_BITMAP(high, KVMI_NUM_MSR);
+ } kvm_mask;
+ bool (*monitor_fct)(struct kvm_vcpu *vcpu, u32 msr,
+ bool enable);
} msrw;
};
@@ -61,6 +67,8 @@ void kvmi_xsetbv_event(struct kvm_vcpu *vcpu, u8 xcr,
bool kvmi_monitor_desc_intercept(struct kvm_vcpu *vcpu, bool enable);
bool kvmi_descriptor_event(struct kvm_vcpu *vcpu, u8 descriptor, bool write);
bool kvmi_msr_event(struct kvm_vcpu *vcpu, struct msr_data *msr);
+bool kvmi_monitor_msrw_intercept(struct kvm_vcpu *vcpu, u32 msr, bool enable);
+bool kvmi_msrw_intercept_originator(struct kvm_vcpu *vcpu);
#else /* CONFIG_KVM_INTROSPECTION */
@@ -82,6 +90,10 @@ static inline bool kvmi_descriptor_event(struct kvm_vcpu
*vcpu, u8 descriptor,
bool write) { return true; }
static inline bool kvmi_msr_event(struct kvm_vcpu *vcpu, struct msr_data *msr)
{ return true; }
+static inline bool kvmi_monitor_msrw_intercept(struct kvm_vcpu *vcpu, u32 msr,
+ bool enable) { return false; }
+static inline bool kvmi_msrw_intercept_originator(struct kvm_vcpu *vcpu)
+ { return false; }
#endif /* CONFIG_KVM_INTROSPECTION */
diff --git a/arch/x86/kvm/kvmi.c b/arch/x86/kvm/kvmi.c
index c84a140db451..4e25ffc3d131 100644
--- a/arch/x86/kvm/kvmi.c
+++ b/arch/x86/kvm/kvmi.c
@@ -345,22 +345,25 @@ static void kvmi_arch_disable_desc_intercept(struct
kvm_vcpu *vcpu)
vcpu->arch.kvmi->descriptor.kvm_intercepted = false;
}
-static unsigned long *msr_mask(struct kvm_vcpu *vcpu, unsigned int *msr)
+static unsigned long *msr_mask(struct kvm_vcpu *vcpu, unsigned int *msr,
+ bool kvmi)
{
switch (*msr) {
case 0 ... 0x1fff:
- return vcpu->arch.kvmi->msrw.kvmi_mask.low;
+ return kvmi ? vcpu->arch.kvmi->msrw.kvmi_mask.low :
+ vcpu->arch.kvmi->msrw.kvm_mask.low;
case 0xc0000000 ... 0xc0001fff:
*msr &= 0x1fff;
- return vcpu->arch.kvmi->msrw.kvmi_mask.high;
+ return kvmi ? vcpu->arch.kvmi->msrw.kvmi_mask.high :
+ vcpu->arch.kvmi->msrw.kvm_mask.high;
}
return NULL;
}
-static bool test_msr_mask(struct kvm_vcpu *vcpu, unsigned int msr)
+static bool test_msr_mask(struct kvm_vcpu *vcpu, unsigned int msr, bool kvmi)
{
- unsigned long *mask = msr_mask(vcpu, &msr);
+ unsigned long *mask = msr_mask(vcpu, &msr, kvmi);
if (!mask)
return false;
@@ -368,9 +371,27 @@ static bool test_msr_mask(struct kvm_vcpu *vcpu, unsigned
int msr)
return !!test_bit(msr, mask);
}
-static bool msr_control(struct kvm_vcpu *vcpu, unsigned int msr, bool enable)
+/*
+ * Returns true if one side (kvm or kvmi) tries to disable the MSR write
+ * interception while the other side is still tracking it.
+ */
+bool kvmi_monitor_msrw_intercept(struct kvm_vcpu *vcpu, u32 msr, bool enable)
+{
+ struct kvmi_interception *arch_vcpui;
+
+ if (!vcpu)
+ return false;
+
+ arch_vcpui = READ_ONCE(vcpu->arch.kvmi);
+
+ return (arch_vcpui && arch_vcpui->msrw.monitor_fct(vcpu, msr, enable));
+}
+EXPORT_SYMBOL(kvmi_monitor_msrw_intercept);
+
+static bool msr_control(struct kvm_vcpu *vcpu, unsigned int msr, bool enable,
+ bool kvmi)
{
- unsigned long *mask = msr_mask(vcpu, &msr);
+ unsigned long *mask = msr_mask(vcpu, &msr, kvmi);
if (!mask)
return false;
@@ -383,6 +404,63 @@ static bool msr_control(struct kvm_vcpu *vcpu, unsigned
int msr, bool enable)
return true;
}
+static bool msr_intercepted_by_kvmi(struct kvm_vcpu *vcpu, u32 msr)
+{
+ return test_msr_mask(vcpu, msr, true);
+}
+
+static bool msr_intercepted_by_kvm(struct kvm_vcpu *vcpu, u32 msr)
+{
+ return test_msr_mask(vcpu, msr, false);
+}
+
+static void record_msr_intercept_status_for_kvmi(struct kvm_vcpu *vcpu, u32
msr,
+ bool enable)
+{
+ msr_control(vcpu, msr, enable, true);
+}
+
+static void record_msr_intercept_status_for_kvm(struct kvm_vcpu *vcpu, u32 msr,
+ bool enable)
+{
+ msr_control(vcpu, msr, enable, false);
+}
+
+static bool monitor_msrw_fct_kvmi(struct kvm_vcpu *vcpu, u32 msr, bool enable)
+{
+ bool ret = false;
+
+ if (enable) {
+ if (static_call(kvm_x86_msr_write_intercepted)(vcpu, msr))
+ record_msr_intercept_status_for_kvm(vcpu, msr, true);
+ } else {
+ if (unlikely(!msr_intercepted_by_kvmi(vcpu, msr)))
+ ret = true;
+
+ if (msr_intercepted_by_kvm(vcpu, msr))
+ ret = true;
+ }
+
+ record_msr_intercept_status_for_kvmi(vcpu, msr, enable);
+
+ return ret;
+}
+
+static bool monitor_msrw_fct_kvm(struct kvm_vcpu *vcpu, u32 msr, bool enable)
+{
+ bool ret = false;
+
+ if (!(msr_intercepted_by_kvmi(vcpu, msr)))
+ return false;
+
+ if (!enable)
+ ret = true;
+
+ record_msr_intercept_status_for_kvm(vcpu, msr, enable);
+
+ return ret;
+}
+
static unsigned int msr_mask_to_base(struct kvm_vcpu *vcpu, unsigned long
*mask)
{
if (mask == vcpu->arch.kvmi->msrw.kvmi_mask.high)
@@ -393,13 +471,14 @@ static unsigned int msr_mask_to_base(struct kvm_vcpu
*vcpu, unsigned long *mask)
void kvmi_control_msrw_intercept(struct kvm_vcpu *vcpu, u32 msr, bool enable)
{
+ vcpu->arch.kvmi->msrw.monitor_fct = monitor_msrw_fct_kvmi;
static_call(kvm_x86_control_msr_intercept)(vcpu, msr, MSR_TYPE_W,
enable);
- msr_control(vcpu, msr, enable);
+ vcpu->arch.kvmi->msrw.monitor_fct = monitor_msrw_fct_kvm;
}
-static void kvmi_arch_disable_msr_intercept(struct kvm_vcpu *vcpu,
- unsigned long *mask)
+static void kvmi_arch_disable_msrw_intercept(struct kvm_vcpu *vcpu,
+ unsigned long *mask)
{
unsigned int msr_base = msr_mask_to_base(vcpu, mask);
int offset = -1;
@@ -410,8 +489,7 @@ static void kvmi_arch_disable_msr_intercept(struct kvm_vcpu
*vcpu,
if (offset >= KVMI_NUM_MSR)
break;
- static_call(kvm_x86_control_msr_intercept)(vcpu,
- msr_base + offset, MSR_TYPE_W, false);
+ kvmi_control_msrw_intercept(vcpu, msr_base + offset, false);
}
bitmap_zero(mask, KVMI_NUM_MSR);
@@ -463,8 +541,8 @@ static void kvmi_arch_restore_interception(struct kvm_vcpu
*vcpu)
kvmi_arch_disable_bp_intercept(vcpu);
kvmi_arch_disable_cr3w_intercept(vcpu);
kvmi_arch_disable_desc_intercept(vcpu);
- kvmi_arch_disable_msr_intercept(vcpu, arch_vcpui->msrw.kvmi_mask.low);
- kvmi_arch_disable_msr_intercept(vcpu, arch_vcpui->msrw.kvmi_mask.high);
+ kvmi_arch_disable_msrw_intercept(vcpu, arch_vcpui->msrw.kvmi_mask.low);
+ kvmi_arch_disable_msrw_intercept(vcpu, arch_vcpui->msrw.kvmi_mask.high);
}
bool kvmi_arch_clean_up_interception(struct kvm_vcpu *vcpu)
@@ -491,12 +569,14 @@ bool kvmi_arch_vcpu_alloc_interception(struct kvm_vcpu
*vcpu)
arch_vcpui->breakpoint.monitor_fct = monitor_bp_fct_kvm;
arch_vcpui->cr3w.monitor_fct = monitor_cr3w_fct_kvm;
arch_vcpui->descriptor.monitor_fct = monitor_desc_fct_kvm;
+ arch_vcpui->msrw.monitor_fct = monitor_msrw_fct_kvm;
/*
* paired with:
* - kvmi_monitor_bp_intercept()
* - kvmi_monitor_cr3w_intercept()
* - kvmi_monitor_desc_intercept()
+ * - kvmi_monitor_msrw_intercept()
*/
smp_wmb();
WRITE_ONCE(vcpu->arch.kvmi, arch_vcpui);
@@ -778,6 +858,20 @@ bool kvmi_descriptor_event(struct kvm_vcpu *vcpu, u8
descriptor, bool write)
}
EXPORT_SYMBOL(kvmi_descriptor_event);
+bool kvmi_msrw_intercept_originator(struct kvm_vcpu *vcpu)
+{
+ struct kvmi_interception *arch_vcpui;
+
+ if (!vcpu)
+ return false;
+
+ arch_vcpui = READ_ONCE(vcpu->arch.kvmi);
+
+ return (arch_vcpui &&
+ arch_vcpui->msrw.monitor_fct == monitor_msrw_fct_kvmi);
+}
+EXPORT_SYMBOL(kvmi_msrw_intercept_originator);
+
static bool __kvmi_msr_event(struct kvm_vcpu *vcpu, struct msr_data *msr)
{
struct msr_data old_msr = {
@@ -788,7 +882,7 @@ static bool __kvmi_msr_event(struct kvm_vcpu *vcpu, struct
msr_data *msr)
u32 action;
bool ret;
- if (!test_msr_mask(vcpu, msr->index))
+ if (!test_msr_mask(vcpu, msr->index, true))
return true;
if (static_call(kvm_x86_get_msr)(vcpu, &old_msr))
return true;
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index d3d061615536..ea2843027671 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -673,6 +673,16 @@ static void set_msr_interception_bitmap(struct kvm_vcpu
*vcpu, u32 *msrpm,
unsigned long tmp;
u32 offset;
+#ifdef CONFIG_KVM_INTROSPECTION
+ if ((type & MSR_TYPE_W) &&
+ kvmi_monitor_msrw_intercept(vcpu, msr, !value))
+ type &= ~MSR_TYPE_W;
+
+ /*
+ * Avoid the below warning for kvmi intercepted msrs.
+ */
+ if (!kvmi_msrw_intercept_originator(vcpu))
+#endif /* CONFIG_KVM_INTROSPECTION */
/*
* If this warning triggers extend the direct_access_msrs list at the
* beginning of the file
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 964840430537..1df0a29d1d8d 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -3798,6 +3798,12 @@ void vmx_disable_intercept_for_msr(struct kvm_vcpu
*vcpu, u32 msr, int type)
if (!cpu_has_vmx_msr_bitmap())
return;
+#ifdef CONFIG_KVM_INTROSPECTION
+ if ((type & MSR_TYPE_W) &&
+ kvmi_monitor_msrw_intercept(vcpu, msr, false))
+ type &= ~MSR_TYPE_W;
+#endif /* CONFIG_KVM_INTROSPECTION */
+
if (static_branch_unlikely(&enable_evmcs))
evmcs_touch_msr_bitmap();
@@ -3843,6 +3849,11 @@ void vmx_enable_intercept_for_msr(struct kvm_vcpu *vcpu,
u32 msr, int type)
if (!cpu_has_vmx_msr_bitmap())
return;
+#ifdef CONFIG_KVM_INTROSPECTION
+ if (type & MSR_TYPE_W)
+ kvmi_monitor_msrw_intercept(vcpu, msr, true);
+#endif /* CONFIG_KVM_INTROSPECTION */
+
if (static_branch_unlikely(&enable_evmcs))
evmcs_touch_msr_bitmap();
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