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Commit b376683f authored by Paul Mackerras's avatar Paul Mackerras Committed by Greg Kroah-Hartman
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KVM: PPC: Book3S: Use new mutex to synchronize access to rtas token list 



[ Upstream commit 1659e27d2bc1ef47b6d031abe01b467f18cb72d9 ]

Currently the Book 3S KVM code uses kvm->lock to synchronize access
to the kvm->arch.rtas_tokens list.  Because this list is scanned
inside kvmppc_rtas_hcall(), which is called with the vcpu mutex held,
taking kvm->lock cause a lock inversion problem, which could lead to
a deadlock.

To fix this, we add a new mutex, kvm->arch.rtas_token_lock, which nests
inside the vcpu mutexes, and use that instead of kvm->lock when
accessing the rtas token list.

This removes the lockdep_assert_held() in kvmppc_rtas_tokens_free().
At this point we don't hold the new mutex, but that is OK because
kvmppc_rtas_tokens_free() is only called when the whole VM is being
destroyed, and at that point nothing can be looking up a token in
the list.

Signed-off-by: default avatarPaul Mackerras <paulus@ozlabs.org>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 4acce744

arch/powerpc/include/asm/kvm_host.h

+1 −0
Original line number Diff line number Diff line
@@ -299,6 +299,7 @@ struct kvm_arch { 
#ifdef CONFIG_PPC_BOOK3S_64

	struct list_head spapr_tce_tables;

	struct list_head rtas_tokens;

	struct mutex rtas_token_lock;

	DECLARE_BITMAP(enabled_hcalls, MAX_HCALL_OPCODE/4 + 1);

#endif

#ifdef CONFIG_KVM_MPIC

arch/powerpc/kvm/book3s.c

+1 −0
Original line number Diff line number Diff line
@@ -840,6 +840,7 @@ int kvmppc_core_init_vm(struct kvm *kvm) 
#ifdef CONFIG_PPC64

	INIT_LIST_HEAD_RCU(&kvm->arch.spapr_tce_tables);

	INIT_LIST_HEAD(&kvm->arch.rtas_tokens);

	mutex_init(&kvm->arch.rtas_token_lock);

#endif



	return kvm->arch.kvm_ops->init_vm(kvm);

arch/powerpc/kvm/book3s_rtas.c

+6 −8
Original line number Diff line number Diff line
@@ -146,7 +146,7 @@ static int rtas_token_undefine(struct kvm *kvm, char *name) 
{

	struct rtas_token_definition *d, *tmp;



	lockdep_assert_held(&kvm->lock);

	lockdep_assert_held(&kvm->arch.rtas_token_lock);



	list_for_each_entry_safe(d, tmp, &kvm->arch.rtas_tokens, list) {

		if (rtas_name_matches(d->handler->name, name)) {
@@ -167,7 +167,7 @@ static int rtas_token_define(struct kvm *kvm, char *name, u64 token) 
	bool found;

	int i;



	lockdep_assert_held(&kvm->lock);

	lockdep_assert_held(&kvm->arch.rtas_token_lock);



	list_for_each_entry(d, &kvm->arch.rtas_tokens, list) {

		if (d->token == token)
@@ -206,14 +206,14 @@ int kvm_vm_ioctl_rtas_define_token(struct kvm *kvm, void __user *argp) 
	if (copy_from_user(&args, argp, sizeof(args)))

		return -EFAULT;



	mutex_lock(&kvm->lock);

	mutex_lock(&kvm->arch.rtas_token_lock);



	if (args.token)

		rc = rtas_token_define(kvm, args.name, args.token);

	else

		rc = rtas_token_undefine(kvm, args.name);



	mutex_unlock(&kvm->lock);

	mutex_unlock(&kvm->arch.rtas_token_lock);



	return rc;

}
@@ -245,7 +245,7 @@ int kvmppc_rtas_hcall(struct kvm_vcpu *vcpu) 
	orig_rets = args.rets;

	args.rets = &args.args[be32_to_cpu(args.nargs)];



	mutex_lock(&vcpu->kvm->lock);

	mutex_lock(&vcpu->kvm->arch.rtas_token_lock);



	rc = -ENOENT;

	list_for_each_entry(d, &vcpu->kvm->arch.rtas_tokens, list) {
@@ -256,7 +256,7 @@ int kvmppc_rtas_hcall(struct kvm_vcpu *vcpu) 
		}

	}



	mutex_unlock(&vcpu->kvm->lock);

	mutex_unlock(&vcpu->kvm->arch.rtas_token_lock);



	if (rc == 0) {

		args.rets = orig_rets;
@@ -282,8 +282,6 @@ void kvmppc_rtas_tokens_free(struct kvm *kvm) 
{

	struct rtas_token_definition *d, *tmp;



	lockdep_assert_held(&kvm->lock);



	list_for_each_entry_safe(d, tmp, &kvm->arch.rtas_tokens, list) {

		list_del(&d->list);

		kfree(d);