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authorSean Christopherson <seanjc@google.com>2022-04-15 00:43:43 +0000
committerPaolo Bonzini <pbonzini@redhat.com>2022-04-21 13:16:11 -0400
commit2031f2876896d82aca7e82f84accd9181b9587fb (patch)
tree3738b7477aeb1e7436fa3a01a0a3ff63d0266952 /include
parentfdd6f6ac2e489b9b256cd05a880d13bfdbac7c2e (diff)
KVM: Add helpers to wrap vcpu->srcu_idx and yell if it's abused
Add wrappers to acquire/release KVM's SRCU lock when stashing the index in vcpu->src_idx, along with rudimentary detection of illegal usage, e.g. re-acquiring SRCU and thus overwriting vcpu->src_idx. Because the SRCU index is (currently) either 0 or 1, illegal nesting bugs can go unnoticed for quite some time and only cause problems when the nested lock happens to get a different index. Wrap the WARNs in PROVE_RCU=y, and make them ONCE, otherwise KVM will likely yell so loudly that it will bring the kernel to its knees. Signed-off-by: Sean Christopherson <seanjc@google.com> Tested-by: Fabiano Rosas <farosas@linux.ibm.com> Message-Id: <20220415004343.2203171-4-seanjc@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'include')
-rw-r--r--include/linux/kvm_host.h24
1 files changed, 23 insertions, 1 deletions
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 3f9b22c4983a..2dab4b696682 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -315,7 +315,10 @@ struct kvm_vcpu {
int cpu;
int vcpu_id; /* id given by userspace at creation */
int vcpu_idx; /* index in kvm->vcpus array */
- int srcu_idx;
+ int ____srcu_idx; /* Don't use this directly. You've been warned. */
+#ifdef CONFIG_PROVE_RCU
+ int srcu_depth;
+#endif
int mode;
u64 requests;
unsigned long guest_debug;
@@ -840,6 +843,25 @@ static inline void kvm_vm_bugged(struct kvm *kvm)
unlikely(__ret); \
})
+static inline void kvm_vcpu_srcu_read_lock(struct kvm_vcpu *vcpu)
+{
+#ifdef CONFIG_PROVE_RCU
+ WARN_ONCE(vcpu->srcu_depth++,
+ "KVM: Illegal vCPU srcu_idx LOCK, depth=%d", vcpu->srcu_depth - 1);
+#endif
+ vcpu->____srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
+}
+
+static inline void kvm_vcpu_srcu_read_unlock(struct kvm_vcpu *vcpu)
+{
+ srcu_read_unlock(&vcpu->kvm->srcu, vcpu->____srcu_idx);
+
+#ifdef CONFIG_PROVE_RCU
+ WARN_ONCE(--vcpu->srcu_depth,
+ "KVM: Illegal vCPU srcu_idx UNLOCK, depth=%d", vcpu->srcu_depth);
+#endif
+}
+
static inline bool kvm_dirty_log_manual_protect_and_init_set(struct kvm *kvm)
{
return !!(kvm->manual_dirty_log_protect & KVM_DIRTY_LOG_INITIALLY_SET);