KVM: PPC: Use RCU for arch.spapr_tce_tables
At the moment only spapr_tce_tables updates are protected against races
but not lookups. This fixes missing protection by using RCU for the list.
As lookups also happen in real mode, this uses
list_for_each_entry_lockless() (which is expected not to access any
vmalloc'd memory).
This converts release_spapr_tce_table() to a RCU scheduled handler.
Signed-off-by: Alexey Kardashevskiy <[email protected]>
Reviewed-by: David Gibson <[email protected]>
Signed-off-by: Paul Mackerras <[email protected]>
diff --git a/arch/powerpc/kvm/book3s_64_vio.c b/arch/powerpc/kvm/book3s_64_vio.c
index 54cf9bc94..9526c34 100644
--- a/arch/powerpc/kvm/book3s_64_vio.c
+++ b/arch/powerpc/kvm/book3s_64_vio.c
@@ -45,19 +45,16 @@
* sizeof(u64), PAGE_SIZE) / PAGE_SIZE;
}
-static void release_spapr_tce_table(struct kvmppc_spapr_tce_table *stt)
+static void release_spapr_tce_table(struct rcu_head *head)
{
- struct kvm *kvm = stt->kvm;
+ struct kvmppc_spapr_tce_table *stt = container_of(head,
+ struct kvmppc_spapr_tce_table, rcu);
int i;
- mutex_lock(&kvm->lock);
- list_del(&stt->list);
for (i = 0; i < kvmppc_stt_npages(stt->window_size); i++)
__free_page(stt->pages[i]);
- kfree(stt);
- mutex_unlock(&kvm->lock);
- kvm_put_kvm(kvm);
+ kfree(stt);
}
static int kvm_spapr_tce_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
@@ -88,7 +85,12 @@
{
struct kvmppc_spapr_tce_table *stt = filp->private_data;
- release_spapr_tce_table(stt);
+ list_del_rcu(&stt->list);
+
+ kvm_put_kvm(stt->kvm);
+
+ call_rcu(&stt->rcu, release_spapr_tce_table);
+
return 0;
}
@@ -131,7 +133,7 @@
kvm_get_kvm(kvm);
mutex_lock(&kvm->lock);
- list_add(&stt->list, &kvm->arch.spapr_tce_tables);
+ list_add_rcu(&stt->list, &kvm->arch.spapr_tce_tables);
mutex_unlock(&kvm->lock);
