On Thu, Jan 21, 2016 at 06:39:33PM +1100, Alexey Kardashevskiy wrote:
> At the moment spapr_tce_tables is not protected against races.
That's not really true - it's protected by the kvm->lock mutex.
> This makes
> use of RCU-variants of list helpers. As some bits are executed in real
> mode, this makes use of just introduced list_for_each_entry_rcu_notrace().
>
> This converts release_spapr_tce_table() to a RCU scheduled handler.
The change itself is fine, though.
> Signed-off-by: Alexey Kardashevskiy <aik@xxxxxxxxx>
> Reviewed-by: David Gibson <david@xxxxxxxxxxxxxxxxxxxxx>
> ---
> arch/powerpc/include/asm/kvm_host.h | 1 +
> arch/powerpc/kvm/book3s.c | 2 +-
> arch/powerpc/kvm/book3s_64_vio.c | 20 +++++++++++---------
> 3 files changed, 13 insertions(+), 10 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
> index 271fefb..c7ee696 100644
> --- a/arch/powerpc/include/asm/kvm_host.h
> +++ b/arch/powerpc/include/asm/kvm_host.h
> @@ -184,6 +184,7 @@ struct kvmppc_spapr_tce_table {
> struct kvm *kvm;
> u64 liobn;
> u32 window_size;
> + struct rcu_head rcu;
> struct page *pages[0];
> };
>
> diff --git a/arch/powerpc/kvm/book3s.c b/arch/powerpc/kvm/book3s.c
> index 638c6d9..b34220d 100644
> --- a/arch/powerpc/kvm/book3s.c
> +++ b/arch/powerpc/kvm/book3s.c
> @@ -807,7 +807,7 @@ int kvmppc_core_init_vm(struct kvm *kvm)
> {
>
> #ifdef CONFIG_PPC64
> - INIT_LIST_HEAD(&kvm->arch.spapr_tce_tables);
> + INIT_LIST_HEAD_RCU(&kvm->arch.spapr_tce_tables);
> INIT_LIST_HEAD(&kvm->arch.rtas_tokens);
> #endif
>
> diff --git a/arch/powerpc/kvm/book3s_64_vio.c b/arch/powerpc/kvm/book3s_64_vio.c
> index 54cf9bc..9526c34 100644
> --- a/arch/powerpc/kvm/book3s_64_vio.c
> +++ b/arch/powerpc/kvm/book3s_64_vio.c
> @@ -45,19 +45,16 @@ static long kvmppc_stt_npages(unsigned long window_size)
> * 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);
> }
>
> static int kvm_spapr_tce_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
> @@ -88,7 +85,12 @@ static int kvm_spapr_tce_release(struct inode *inode, struct file *filp)
> {
> 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 @@ long kvm_vm_ioctl_create_spapr_tce(struct kvm *kvm,
> 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);
>
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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