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From:   Halil Pasic <pasic@linux.ibm.com>
To:     Christian Borntraeger <borntraeger@de.ibm.com>,
        Janosch Frank <frankja@linux.ibm.com>,
        David Hildenbrand <david@redhat.com>,
        Cornelia Huck <cohuck@redhat.com>,
        Claudio Imbrenda <imbrenda@linux.ibm.com>,
        Heiko Carstens <hca@linux.ibm.com>,
        Vasily Gorbik <gor@linux.ibm.com>, kvm@vger.kernel.org,
        linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org
Cc:     Halil Pasic <pasic@linux.ibm.com>, stable@vger.kernel.org,
        Michael Mueller <mimu@linux.ibm.com>
Subject: [PATCH 1/1] KVM: s390: index kvm->arch.idle_mask by vcpu_idx
Date:   Fri, 27 Aug 2021 14:54:29 +0200
Message-Id: <20210827125429.1912577-1-pasic@linux.ibm.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

While in practice vcpu->vcpu_idx ==  vcpu->vcp_id is often true,
it may not always be, and we must not rely on this.

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. 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.

Signed-off-by: Halil Pasic <pasic@linux.ibm.com>
Fixes: 1ee0bc559dc3 ("KVM: s390: get rid of local_int array")
Cc: <stable@vger.kernel.org> # 3.15+
---
 arch/s390/include/asm/kvm_host.h |  1 +
 arch/s390/kvm/interrupt.c        | 12 ++++++------
 arch/s390/kvm/kvm-s390.c         |  2 +-
 arch/s390/kvm/kvm-s390.h         |  2 +-
 4 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index 161a9e12bfb8..630eab0fa176 100644
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -957,6 +957,7 @@ struct kvm_arch{
 	atomic64_t cmma_dirty_pages;
 	/* subset of available cpu features enabled by user space */
 	DECLARE_BITMAP(cpu_feat, KVM_S390_VM_CPU_FEAT_NR_BITS);
+	/* indexed by vcpu_idx */
 	DECLARE_BITMAP(idle_mask, KVM_MAX_VCPUS);
 	struct kvm_s390_gisa_interrupt gisa_int;
 	struct kvm_s390_pv pv;
diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
index d548d60caed2..16256e17a544 100644
--- a/arch/s390/kvm/interrupt.c
+++ b/arch/s390/kvm/interrupt.c
@@ -419,13 +419,13 @@ 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.idle_mask);
+	set_bit(kvm_vcpu_get_idx(vcpu), vcpu->kvm->arch.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.idle_mask);
+	clear_bit(kvm_vcpu_get_idx(vcpu), vcpu->kvm->arch.idle_mask);
 }
 
 static void __reset_intercept_indicators(struct kvm_vcpu *vcpu)
@@ -3050,18 +3050,18 @@ int kvm_s390_get_irq_state(struct kvm_vcpu *vcpu, __u8 __user *buf, int len)
 
 static void __airqs_kick_single_vcpu(struct kvm *kvm, u8 deliverable_mask)
 {
-	int vcpu_id, online_vcpus = atomic_read(&kvm->online_vcpus);
+	int vcpu_idx, online_vcpus = atomic_read(&kvm->online_vcpus);
 	struct kvm_s390_gisa_interrupt *gi = &kvm->arch.gisa_int;
 	struct kvm_vcpu *vcpu;
 
-	for_each_set_bit(vcpu_id, kvm->arch.idle_mask, online_vcpus) {
-		vcpu = kvm_get_vcpu(kvm, vcpu_id);
+	for_each_set_bit(vcpu_idx, kvm->arch.idle_mask, online_vcpus) {
+		vcpu = kvm_get_vcpu(kvm, vcpu_idx);
 		if (psw_ioint_disabled(vcpu))
 			continue;
 		deliverable_mask &= (u8)(vcpu->arch.sie_block->gcr[6] >> 24);
 		if (deliverable_mask) {
 			/* lately kicked but not yet running */
-			if (test_and_set_bit(vcpu_id, gi->kicked_mask))
+			if (test_and_set_bit(vcpu_idx, gi->kicked_mask))
 				return;
 			kvm_s390_vcpu_wakeup(vcpu);
 			return;
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 4527ac7b5961..8580543c5bc3 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -4044,7 +4044,7 @@ static int vcpu_pre_run(struct kvm_vcpu *vcpu)
 		kvm_s390_patch_guest_per_regs(vcpu);
 	}
 
-	clear_bit(vcpu->vcpu_id, vcpu->kvm->arch.gisa_int.kicked_mask);
+	clear_bit(kvm_vcpu_get_idx(vcpu), vcpu->kvm->arch.gisa_int.kicked_mask);
 
 	vcpu->arch.sie_block->icptcode = 0;
 	cpuflags = atomic_read(&vcpu->arch.sie_block->cpuflags);
diff --git a/arch/s390/kvm/kvm-s390.h b/arch/s390/kvm/kvm-s390.h
index 9fad25109b0d..ecd741ee3276 100644
--- a/arch/s390/kvm/kvm-s390.h
+++ b/arch/s390/kvm/kvm-s390.h
@@ -79,7 +79,7 @@ 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.idle_mask);
+	return test_bit(kvm_vcpu_get_idx(vcpu), vcpu->kvm->arch.idle_mask);
 }
 
 static inline int kvm_is_ucontrol(struct kvm *kvm)

base-commit: 77dd11439b86e3f7990e4c0c9e0b67dca82750ba
-- 
2.25.1