Re: [PATCH v5 07/12] Maintain memslot version number

Avi Kivity
2010-08-23T15:53:58Z

On 07/19/2010 06:30 PM, Gleb Natapov wrote:
> Code that depends on particular memslot layout can track changes and
> adjust to new layout.
>
>
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index c13cc48..c74ffc0 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -177,6 +177,7 @@ struct kvm {
> raw_spinlock_t requests_lock;
> struct mutex slots_lock;
> struct mm_struct *mm; /* userspace tied to this vm */
> + u32 memslot_version;
> struct kvm_memslots *memslots;
> struct srcu_struct srcu;
> #ifdef CONFIG_KVM_APIC_ARCHITECTURE
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index b78b794..292514c 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -733,6 +733,7 @@ skip_lpage:
> slots->memslots[mem->slot] = new;
> old_memslots = kvm->memslots;
> rcu_assign_pointer(kvm->memslots, slots);
> + kvm->memslot_version++;
> synchronize_srcu_expedited(&kvm->srcu);
>
> kvm_arch_commit_memory_region(kvm, mem, old, user_alloc);

How does this interact with rcu? Nothing enforces consistency between
rcu_dereference(kvm->memslots) and kvm->memslot_version.

Should probably be rcu_dereference(kvm->memslots)->version.

--
error compiling committee.c: too many arguments to function