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FAILED: patch "[PATCH] KVM: s390: index kvm->arch.idle_mask by vcpu_idx" failed to apply to 4.9-stable tree

PATCH [email protected] 1 participant 1 message Sep 13, 2021

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The patch below does not apply to the 4.9-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From a3e03bc1368c1bc16e19b001fc96dc7430573cc8 Mon Sep 17 00:00:00 2001
From: Halil Pasic <[email protected]>
Date: Fri, 27 Aug 2021 14:54:29 +0200
Subject: [PATCH] KVM: s390: index kvm->arch.idle_mask by vcpu_idx
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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 <[email protected]>
Reviewed-by Christian Bornträger <[email protected]>
Reviewed-by Claudio Imbrenda <[email protected]>
Cc <[email protected]> # 3.15+
Link https://lore.kernel.org/r/[email protected] open here
Signed-off-by Christian Borntraeger <[email protected]>
arch/s390/include/asm/kvm_host.h +1 -0
index 118d5450c523..611f18ecde91 100644
@@ -963,6 +963,7 @@ 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;
arch/s390/kvm/interrupt.c +6 -6
index d548d60caed2..16256e17a544 100644
@@ -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;
arch/s390/kvm/kvm-s390.c +1 -1
index 5b45c83ced21..e144c8046ceb 100644
@@ -4026,7 +4026,7 @@ 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);
arch/s390/kvm/kvm-s390.h +1 -1
index 9fad25109b0d..ecd741ee3276 100644
@@ -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)