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authorPaul Mackerras <paulus@ozlabs.org>2019-05-29 11:54:00 +1000
committerPaul Gortmaker <paul.gortmaker@windriver.com>2019-09-16 12:21:41 -0400
commit6de06a0e679314f188dddefb073131019c077b93 (patch)
tree7a45ce6b287a57ab88b9e49fc0c3228c898e8ee9
parent7cf39793612d9071edfcf6c02cb22a7a859dd4cc (diff)
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KVM: PPC: Book3S: Use new mutex to synchronize access to rtas token list
commit 1659e27d2bc1ef47b6d031abe01b467f18cb72d9 upstream. 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: Paul Gortmaker <paul.gortmaker@windriver.com>
-rw-r--r--arch/powerpc/include/asm/kvm_host.h1
-rw-r--r--arch/powerpc/kvm/book3s.c1
-rw-r--r--arch/powerpc/kvm/book3s_rtas.c14
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 68f69854095b..5a5c207f7ad2 100644
--- a/arch/powerpc/include/asm/kvm_host.h
+++ b/arch/powerpc/include/asm/kvm_host.h
@@ -292,6 +292,7 @@ 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 edaf4720d156..5b95ef13abd6 100644
--- a/arch/powerpc/kvm/book3s.c
+++ b/arch/powerpc/kvm/book3s.c
@@ -841,6 +841,7 @@ 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);