KVM: x86: Rename interrupt.pending to interrupt.injected

For exceptions & NMIs events, KVM code use the following
coding convention:
*) "pending" represents an event that should be injected to guest at
some point but it's side-effects have not yet occurred.
*) "injected" represents an event that it's side-effects have already
occurred.

However, interrupts don't conform to this coding convention.
All current code flows mark interrupt.pending when it's side-effects
have already taken place (For example, bit moved from LAPIC IRR to
ISR). Therefore, it makes sense to just rename
interrupt.pending to interrupt.injected.

This change follows logic of previous commit 664f8e26b00c ("KVM: X86:
Fix loss of exception which has not yet been injected") which changed
exception to follow this coding convention as well.

It is important to note that in case !lapic_in_kernel(vcpu),
interrupt.pending usage was and still incorrect.
In this case, interrrupt.pending can only be set using one of the
following ioctls: KVM_INTERRUPT, KVM_SET_VCPU_EVENTS and
KVM_SET_SREGS. Looking at how QEMU uses these ioctls, one can see that
QEMU uses them either to re-set an "interrupt.pending" state it has
received from KVM (via KVM_GET_VCPU_EVENTS interrupt.pending or
via KVM_GET_SREGS interrupt_bitmap) or by dispatching a new interrupt
from QEMU's emulated LAPIC which reset bit in IRR and set bit in ISR
before sending ioctl to KVM. So it seems that indeed "interrupt.pending"
in this case is also suppose to represent "interrupt.injected".
However, kvm_cpu_has_interrupt() & kvm_cpu_has_injectable_intr()
is misusing (now named) interrupt.injected in order to return if
there is a pending interrupt.
This leads to nVMX/nSVM not be able to distinguish if it should exit
from L2 to L1 on EXTERNAL_INTERRUPT on pending interrupt or should
re-inject an injected interrupt.
Therefore, add a FIXME at these functions for handling this issue.

This patch introduce no semantics change.

Signed-off-by: Liran Alon <liran.alon@oracle.com>
Reviewed-by: Nikita Leshenko <nikita.leshchenko@oracle.com>
Reviewed-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Krish Sadhukhan <krish.sadhukhan@oracle.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>

1 files changed, 24 insertions, 2 deletions

diff --git a/arch/x86/kvm/irq.c b/arch/x86/kvm/irq.c
index f171051eecf3..faa264822cee 100644
--- a/arch/x86/kvm/irq.c
+++ b/arch/x86/kvm/irq.c
@@ -73,8 +73,19 @@ static int kvm_cpu_has_extint(struct kvm_vcpu *v)
  */
 int kvm_cpu_has_injectable_intr(struct kvm_vcpu *v)
 {
+	/*
+	 * FIXME: interrupt.injected represents an interrupt that it's
+	 * side-effects have already been applied (e.g. bit from IRR
+	 * already moved to ISR). Therefore, it is incorrect to rely
+	 * on interrupt.injected to know if there is a pending
+	 * interrupt in the user-mode LAPIC.
+	 * This leads to nVMX/nSVM not be able to distinguish
+	 * if it should exit from L2 to L1 on EXTERNAL_INTERRUPT on
+	 * pending interrupt or should re-inject an injected
+	 * interrupt.
+	 */
 	if (!lapic_in_kernel(v))
-		return v->arch.interrupt.pending;
+		return v->arch.interrupt.injected;
 
 	if (kvm_cpu_has_extint(v))
 		return 1;
@@ -91,8 +102,19 @@ int kvm_cpu_has_injectable_intr(struct kvm_vcpu *v)
  */
 int kvm_cpu_has_interrupt(struct kvm_vcpu *v)
 {
+	/*
+	 * FIXME: interrupt.injected represents an interrupt that it's
+	 * side-effects have already been applied (e.g. bit from IRR
+	 * already moved to ISR). Therefore, it is incorrect to rely
+	 * on interrupt.injected to know if there is a pending
+	 * interrupt in the user-mode LAPIC.
+	 * This leads to nVMX/nSVM not be able to distinguish
+	 * if it should exit from L2 to L1 on EXTERNAL_INTERRUPT on
+	 * pending interrupt or should re-inject an injected
+	 * interrupt.
+	 */
 	if (!lapic_in_kernel(v))
-		return v->arch.interrupt.pending;
+		return v->arch.interrupt.injected;
 
 	if (kvm_cpu_has_extint(v))
 		return 1;