Re: [PATCH 2/4] KVM: MMU: support unsync sp out of the protection of 'mmu_lock'

Avi Kivity
2010-09-20T15:20:10Z

On 09/20/2010 04:19 PM, Xiao Guangrong wrote:
> It allows keep unsync sp alive while it's out of the protection, later we can use
> kvm_mmu_free_page() to free it if !sp->active_count

Don't understand. Of course unsync pages exist outside mmu_lock...?

>
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 839852d..4b7af3f 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -996,7 +996,6 @@ static void kvm_mmu_free_page(struct kvm *kvm, struct kvm_mmu_page *sp)
> {
> ASSERT(is_empty_shadow_page(sp->spt));
> hlist_del(&sp->hash_link);
> - list_del(&sp->link);
> __free_page(virt_to_page(sp->spt));
> if (!sp->role.direct)
> __free_page(virt_to_page(sp->gfns));
> @@ -1681,9 +1680,8 @@ static int kvm_mmu_prepare_zap_page(struct kvm *kvm, struct kvm_mmu_page *sp,
> kvm_mmu_unlink_parents(kvm, sp);
> if (!sp->role.invalid&& !sp->role.direct)
> unaccount_shadowed(kvm, sp->gfn);
> - if (sp->unsync)
> - kvm_unlink_unsync_page(kvm, sp);
> - if (!sp->active_count) {
> +
> + if (!sp->active_count || sp->unsync) {
> /* Count self */
> ret++;
> list_move(&sp->link, invalid_list);

How can you drop an active unsync page?

I'm missing something here.

> @@ -1692,6 +1690,8 @@ static int kvm_mmu_prepare_zap_page(struct kvm *kvm, struct kvm_mmu_page *sp,
> kvm_reload_remote_mmus(kvm);
> }
>
> + if (sp->unsync)
> + kvm_unlink_unsync_page(kvm, sp);
> sp->role.invalid = 1;
> kvm_mmu_reset_last_pte_updated(kvm);
> return ret;
> @@ -1709,8 +1709,12 @@ static void kvm_mmu_commit_zap_page(struct kvm *kvm,
>
> do {
> sp = list_first_entry(invalid_list, struct kvm_mmu_page, link);
> - WARN_ON(!sp->role.invalid || sp->active_count);
> - kvm_mmu_free_page(kvm, sp);
> + WARN_ON(!sp->role.invalid);
> + list_del(&sp->link);
> + if (sp->active_count)
> + WARN_ON(!sp->unsync);
> + else
> + kvm_mmu_free_page(kvm, sp);
> } while (!list_empty(invalid_list));
>
> }

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