[RFC PATCH v7 19/23] entry/kvm: Protect the kernel when entering from guest

From: Julien Desfossez
Date: Fri Aug 28 2020 - 15:53:43 EST


From: Vineeth Pillai <viremana@xxxxxxxxxxxxxxxxxxx>

Similar to how user to kernel mode transitions are protected in earlier
patches, protect the entry into kernel from guest mode as well.

Signed-off-by: Vineeth Pillai <viremana@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kvm/x86.c | 3 +++
include/linux/entry-kvm.h | 12 ++++++++++++
kernel/entry/kvm.c | 12 ++++++++++++
3 files changed, 27 insertions(+)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 33945283fe07..2c2f211a556a 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -8526,6 +8526,8 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
*/
smp_mb__after_srcu_read_unlock();

+ kvm_exit_to_guest_mode(vcpu);
+
/*
* This handles the case where a posted interrupt was
* notified with kvm_vcpu_kick.
@@ -8619,6 +8621,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
}
}

+ kvm_enter_from_guest_mode(vcpu);
local_irq_enable();
preempt_enable();

diff --git a/include/linux/entry-kvm.h b/include/linux/entry-kvm.h
index 0cef17afb41a..32aabb7f3e6d 100644
--- a/include/linux/entry-kvm.h
+++ b/include/linux/entry-kvm.h
@@ -77,4 +77,16 @@ static inline bool xfer_to_guest_mode_work_pending(void)
}
#endif /* CONFIG_KVM_XFER_TO_GUEST_WORK */

+/**
+ * kvm_enter_from_guest_mode - Hook called just after entering kernel from guest.
+ * @vcpu: Pointer to the current VCPU data
+ */
+void kvm_enter_from_guest_mode(struct kvm_vcpu *vcpu);
+
+/**
+ * kvm_exit_to_guest_mode - Hook called just before entering guest from kernel.
+ * @vcpu: Pointer to the current VCPU data
+ */
+void kvm_exit_to_guest_mode(struct kvm_vcpu *vcpu);
+
#endif
diff --git a/kernel/entry/kvm.c b/kernel/entry/kvm.c
index eb1a8a4c867c..994af4241646 100644
--- a/kernel/entry/kvm.c
+++ b/kernel/entry/kvm.c
@@ -49,3 +49,15 @@ int xfer_to_guest_mode_handle_work(struct kvm_vcpu *vcpu)
return xfer_to_guest_mode_work(vcpu, ti_work);
}
EXPORT_SYMBOL_GPL(xfer_to_guest_mode_handle_work);
+
+void kvm_enter_from_guest_mode(struct kvm_vcpu *vcpu)
+{
+ sched_core_unsafe_enter();
+}
+EXPORT_SYMBOL_GPL(kvm_enter_from_guest_mode);
+
+void kvm_exit_to_guest_mode(struct kvm_vcpu *vcpu)
+{
+ sched_core_unsafe_exit_wait(XFER_TO_GUEST_MODE_WORK);
+}
+EXPORT_SYMBOL_GPL(kvm_exit_to_guest_mode);
--
2.17.1