releases/4.19.54/kvm-ppc-book3s-use-new-mutex-to-synchronize-access-t.patch

   1 From bc3c51cabd27911f6b6c25722ba71b02de162077 Mon Sep 17 00:00:00 2001
   2 From: Paul Mackerras <paulus@ozlabs.org>
   3 Date: Wed, 29 May 2019 11:54:00 +1000
   4 Subject: KVM: PPC: Book3S: Use new mutex to synchronize access to rtas token
   5  list
   6
   7 [ Upstream commit 1659e27d2bc1ef47b6d031abe01b467f18cb72d9 ]
   8
   9 Currently the Book 3S KVM code uses kvm->lock to synchronize access
  10 to the kvm->arch.rtas_tokens list.  Because this list is scanned
  11 inside kvmppc_rtas_hcall(), which is called with the vcpu mutex held,
  12 taking kvm->lock cause a lock inversion problem, which could lead to
  13 a deadlock.
  14
  15 To fix this, we add a new mutex, kvm->arch.rtas_token_lock, which nests
  16 inside the vcpu mutexes, and use that instead of kvm->lock when
  17 accessing the rtas token list.
  18
  19 This removes the lockdep_assert_held() in kvmppc_rtas_tokens_free().
  20 At this point we don't hold the new mutex, but that is OK because
  21 kvmppc_rtas_tokens_free() is only called when the whole VM is being
  22 destroyed, and at that point nothing can be looking up a token in
  23 the list.
  24
  25 Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
  26 Signed-off-by: Sasha Levin <sashal@kernel.org>
  27 ---
  28  arch/powerpc/include/asm/kvm_host.h |  1 +
  29  arch/powerpc/kvm/book3s.c           |  1 +
  30  arch/powerpc/kvm/book3s_rtas.c      | 14 ++++++--------
  31  3 files changed, 8 insertions(+), 8 deletions(-)
  32
  33 diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
  34 index bccc5051249e..2b6049e83970 100644
  35 --- a/arch/powerpc/include/asm/kvm_host.h
  36 +++ b/arch/powerpc/include/asm/kvm_host.h
  37 @@ -299,6 +299,7 @@ struct kvm_arch {
  38  #ifdef CONFIG_PPC_BOOK3S_64
  39         struct list_head spapr_tce_tables;
  40         struct list_head rtas_tokens;
  41 +       struct mutex rtas_token_lock;
  42         DECLARE_BITMAP(enabled_hcalls, MAX_HCALL_OPCODE/4 + 1);
  43  #endif
  44  #ifdef CONFIG_KVM_MPIC
  45 diff --git a/arch/powerpc/kvm/book3s.c b/arch/powerpc/kvm/book3s.c
  46 index 87348e498c89..281f074581a3 100644
  47 --- a/arch/powerpc/kvm/book3s.c
  48 +++ b/arch/powerpc/kvm/book3s.c
  49 @@ -840,6 +840,7 @@ int kvmppc_core_init_vm(struct kvm *kvm)
  50  #ifdef CONFIG_PPC64
  51         INIT_LIST_HEAD_RCU(&kvm->arch.spapr_tce_tables);
  52         INIT_LIST_HEAD(&kvm->arch.rtas_tokens);
  53 +       mutex_init(&kvm->arch.rtas_token_lock);
  54  #endif
  55
  56         return kvm->arch.kvm_ops->init_vm(kvm);
  57 diff --git a/arch/powerpc/kvm/book3s_rtas.c b/arch/powerpc/kvm/book3s_rtas.c
  58 index 2d3b2b1cc272..8f2355138f80 100644
  59 --- a/arch/powerpc/kvm/book3s_rtas.c
  60 +++ b/arch/powerpc/kvm/book3s_rtas.c
  61 @@ -146,7 +146,7 @@ static int rtas_token_undefine(struct kvm *kvm, char *name)
  62  {
  63         struct rtas_token_definition *d, *tmp;
  64
  65 -       lockdep_assert_held(&kvm->lock);
  66 +       lockdep_assert_held(&kvm->arch.rtas_token_lock);
  67
  68         list_for_each_entry_safe(d, tmp, &kvm->arch.rtas_tokens, list) {
  69                 if (rtas_name_matches(d->handler->name, name)) {
  70 @@ -167,7 +167,7 @@ static int rtas_token_define(struct kvm *kvm, char *name, u64 token)
  71         bool found;
  72         int i;
  73
  74 -       lockdep_assert_held(&kvm->lock);
  75 +       lockdep_assert_held(&kvm->arch.rtas_token_lock);
  76
  77         list_for_each_entry(d, &kvm->arch.rtas_tokens, list) {
  78                 if (d->token == token)
  79 @@ -206,14 +206,14 @@ int kvm_vm_ioctl_rtas_define_token(struct kvm *kvm, void __user *argp)
  80         if (copy_from_user(&args, argp, sizeof(args)))
  81                 return -EFAULT;
  82
  83 -       mutex_lock(&kvm->lock);
  84 +       mutex_lock(&kvm->arch.rtas_token_lock);
  85
  86         if (args.token)
  87                 rc = rtas_token_define(kvm, args.name, args.token);
  88         else
  89                 rc = rtas_token_undefine(kvm, args.name);
  90
  91 -       mutex_unlock(&kvm->lock);
  92 +       mutex_unlock(&kvm->arch.rtas_token_lock);
  93
  94         return rc;
  95  }
  96 @@ -245,7 +245,7 @@ int kvmppc_rtas_hcall(struct kvm_vcpu *vcpu)
  97         orig_rets = args.rets;
  98         args.rets = &args.args[be32_to_cpu(args.nargs)];
  99
 100 -       mutex_lock(&vcpu->kvm->lock);
 101 +       mutex_lock(&vcpu->kvm->arch.rtas_token_lock);
 102
 103         rc = -ENOENT;
 104         list_for_each_entry(d, &vcpu->kvm->arch.rtas_tokens, list) {
 105 @@ -256,7 +256,7 @@ int kvmppc_rtas_hcall(struct kvm_vcpu *vcpu)
 106                 }
 107         }
 108
 109 -       mutex_unlock(&vcpu->kvm->lock);
 110 +       mutex_unlock(&vcpu->kvm->arch.rtas_token_lock);
 111
 112         if (rc == 0) {
 113                 args.rets = orig_rets;
 114 @@ -282,8 +282,6 @@ void kvmppc_rtas_tokens_free(struct kvm *kvm)
 115  {
 116         struct rtas_token_definition *d, *tmp;
 117
 118 -       lockdep_assert_held(&kvm->lock);
 119 -
 120         list_for_each_entry_safe(d, tmp, &kvm->arch.rtas_tokens, list) {
 121                 list_del(&d->list);
 122                 kfree(d);
 123 --
 124 2.20.1
 125