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KVM: PPC: Book3S: Use new mutex to synchronize access to rtas token list 

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>
This commit is contained in:
Paul Mackerras 2019-05-29 11:54:00 +10:00
parent 0d4ee88d92
commit 1659e27d2b
3 changed files with 8 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
arch/powerpc/include/asm/kvm_host.h
View File

@ -309,6 +309,7 @@ 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

1
arch/powerpc/kvm/book3s.c
View File

@ -902,6 +902,7 @@ 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);

14
arch/powerpc/kvm/book3s_rtas.c
View File

@ -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);