From: Paul Mackerras paulus@ozlabs.org
[ 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: Paul Mackerras paulus@ozlabs.org Signed-off-by: Sasha Levin sashal@kernel.org --- arch/powerpc/include/asm/kvm_host.h | 1 + arch/powerpc/kvm/book3s.c | 1 + arch/powerpc/kvm/book3s_rtas.c | 14 ++++++-------- 3 files changed, 8 insertions(+), 8 deletions(-)
diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h index e3ba58f64c3d..5070b34b12fd 100644 --- a/arch/powerpc/include/asm/kvm_host.h +++ b/arch/powerpc/include/asm/kvm_host.h @@ -296,6 +296,7 @@ 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 diff --git a/arch/powerpc/kvm/book3s.c b/arch/powerpc/kvm/book3s.c index 72d977e30952..d38280b01ef0 100644 --- a/arch/powerpc/kvm/book3s.c +++ b/arch/powerpc/kvm/book3s.c @@ -836,6 +836,7 @@ 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); diff --git a/arch/powerpc/kvm/book3s_rtas.c b/arch/powerpc/kvm/book3s_rtas.c index 2d3b2b1cc272..8f2355138f80 100644 --- a/arch/powerpc/kvm/book3s_rtas.c +++ b/arch/powerpc/kvm/book3s_rtas.c @@ -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);