[PATCH 1/1] KVM: s390: index kvm->arch.idle_mask by vcpu_idx

[Christian Borntraeger <borntraeger@xxxxxxxxxx>]

From: Halil Pasic <pasic@xxxxxxxxxxxxx>

While in practice vcpu->vcpu_idx ==  vcpu->vcp_id is often true, it may
not always be, and we must not rely on this. Reason is that KVM decides
the vcpu_idx, userspace decides the vcpu_id, thus the two might not
match.

Currently kvm->arch.idle_mask is indexed by vcpu_id, which implies
that code like
for_each_set_bit(vcpu_id, kvm->arch.idle_mask, online_vcpus) {
                vcpu = kvm_get_vcpu(kvm, vcpu_id);
		do_stuff(vcpu);
}
is not legit. Reason is that kvm_get_vcpu expects an vcpu_idx, not an
vcpu_id.  The trouble is, we do actually use kvm->arch.idle_mask like
this. To fix this problem we have two options. Either use
kvm_get_vcpu_by_id(vcpu_id), which would loop to find the right vcpu_id,
or switch to indexing via vcpu_idx. The latter is preferable for obvious
reasons.

Let us make switch from indexing kvm->arch.idle_mask by vcpu_id to
indexing it by vcpu_idx.  To keep gisa_int.kicked_mask indexed by the
same index as idle_mask lets make the same change for it as well.

Fixes: 1ee0bc559dc3 ("KVM: s390: get rid of local_int array")
Signed-off-by: Halil Pasic <pasic@xxxxxxxxxxxxx>
Reviewed-by: Christian Bornträger <borntraeger@xxxxxxxxxx>
Reviewed-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # 3.15+
Link: https://lore.kernel.org/r/20210827125429.1912577-1-pasic@xxxxxxxxxxxxx
Signed-off-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
[borntraeger@xxxxxxxxxx]: change  idle mask, remove kicked_mask 
---
 arch/s390/kvm/interrupt.c | 4 ++--
 arch/s390/kvm/kvm-s390.h  | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
index 3515f2b55eb9..dc5ecaea30d7 100644
--- a/arch/s390/kvm/interrupt.c
+++ b/arch/s390/kvm/interrupt.c
@@ -318,13 +318,13 @@ static unsigned long deliverable_irqs(struct kvm_vcpu *vcpu)
 static void __set_cpu_idle(struct kvm_vcpu *vcpu)
 {
 	kvm_s390_set_cpuflags(vcpu, CPUSTAT_WAIT);
-	set_bit(vcpu->vcpu_id, vcpu->kvm->arch.float_int.idle_mask);
+	set_bit(kvm_vcpu_get_idx(vcpu), vcpu->kvm->arch.float_int.idle_mask);
 }
 
 static void __unset_cpu_idle(struct kvm_vcpu *vcpu)
 {
 	kvm_s390_clear_cpuflags(vcpu, CPUSTAT_WAIT);
-	clear_bit(vcpu->vcpu_id, vcpu->kvm->arch.float_int.idle_mask);
+	clear_bit(kvm_vcpu_get_idx(vcpu), vcpu->kvm->arch.float_int.idle_mask);
 }
 
 static void __reset_intercept_indicators(struct kvm_vcpu *vcpu)
diff --git a/arch/s390/kvm/kvm-s390.h b/arch/s390/kvm/kvm-s390.h
index 981e3ba97461..0a2ffd5378be 100644
--- a/arch/s390/kvm/kvm-s390.h
+++ b/arch/s390/kvm/kvm-s390.h
@@ -67,7 +67,7 @@ static inline int is_vcpu_stopped(struct kvm_vcpu *vcpu)
 
 static inline int is_vcpu_idle(struct kvm_vcpu *vcpu)
 {
-	return test_bit(vcpu->vcpu_id, vcpu->kvm->arch.float_int.idle_mask);
+	return test_bit(kvm_vcpu_get_idx(vcpu), vcpu->kvm->arch.float_int.idle_mask);
 }
 
 static inline int kvm_is_ucontrol(struct kvm *kvm)
-- 
2.31.1