On Wed, Oct 27, 2010 at 05:07:32PM +0800, Xiao Guangrong wrote:
> The current way is queued a complete async pf with:
> asyc_pf.page = bad_page
> async_pf.arch.gfn = 0
>
> It has two problems while kvm_check_async_pf_completion handle this
> async_pf:
> - since !async_pf.page, it can retry a pseudo #PF
kvm_arch_async_page_ready checks for is_error_page()
> - it can delete gfn 0 from vcpu->arch.apf.gfns[]
kvm_arch_async_page_present() checks for is_error_page() too and,
in case of PV guest, injects special token if it is true.
After your patch special token will not be injected and migration will
not work.
> Actually, we can simply record this wakeup request and let
> kvm_check_async_pf_completion simply break the wait
>
May be wakeup_all function naming is misleading. It means wake up all PV
guest processes by sending broadcast async pf notification. It is not
about waking host vcpu thread.
> Signed-off-by: Xiao Guangrong <xiaoguangrong@xxxxxxxxxxxxxx>
> ---
> include/linux/kvm_host.h | 1 +
> virt/kvm/async_pf.c | 21 ++++++---------------
> 2 files changed, 7 insertions(+), 15 deletions(-)
>
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 0c1b7c5..d91add9 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -131,6 +131,7 @@ struct kvm_vcpu {
> struct list_head queue;
> struct list_head done;
> spinlock_t lock;
> + bool wakeup;
> } async_pf;
> #endif
>
> diff --git a/virt/kvm/async_pf.c b/virt/kvm/async_pf.c
> index 5307a32..0d1f6c4 100644
> --- a/virt/kvm/async_pf.c
> +++ b/virt/kvm/async_pf.c
> @@ -124,6 +124,11 @@ bool kvm_check_async_pf_completion(struct kvm_vcpu *vcpu)
> {
> struct kvm_async_pf *work;
>
> + if (vcpu->async_pf.wakeup) {
> + vcpu->async_pf.wakeup = false;
> + return true;
> + }
> +
> if (list_empty_careful(&vcpu->async_pf.done) ||
> !kvm_arch_can_inject_async_page_present(vcpu))
> return false;
> @@ -197,20 +202,6 @@ retry_sync:
>
> int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu)
> {
> - struct kvm_async_pf *work;
> -
> - if (!list_empty(&vcpu->async_pf.done))
> - return 0;
> -
> - work = kmem_cache_zalloc(async_pf_cache, GFP_ATOMIC);
> - if (!work)
> - return -ENOMEM;
> -
> - work->page = bad_page;
> - get_page(bad_page);
> - INIT_LIST_HEAD(&work->queue); /* for list_del to work */
> -
> - list_add_tail(&work->link, &vcpu->async_pf.done);
> - vcpu->async_pf.queued++;
> + vcpu->async_pf.wakeup = true;
> return 0;
> }
> --
> 1.7.0.4
>
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Gleb.
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