Re: [PATCH v9 06/11] xen: Introduce XEN_DOMCTL_soft_reset

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Thu, Jul 16, 2015 at 06:27:21PM +0200, Vitaly Kuznetsov wrote:
> New domctl resets state for a domain allowing it to 'start over': register
> vcpu_info, switch to FIFO ABI for event channels. Still active grants are
> being logged to help debugging misbehaving backends.
> 
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> ---
> Changes since v8:
> - Introduce vcpu_info_reset() helper. [Konrad Rzeszutek Wilk]
> - Take shutdown_lock while checking v->paused_for_shutdown in
>   domain_soft_reset() [Konrad Rzeszutek Wilk]
> ---
>  xen/common/domain.c         | 44 ++++++++++++++++++++++++++++++++++++--------
>  xen/common/domctl.c         |  9 +++++++++
>  xen/include/public/domctl.h |  1 +
>  xen/include/xen/sched.h     |  2 ++
>  4 files changed, 48 insertions(+), 8 deletions(-)
> 
> diff --git a/xen/common/domain.c b/xen/common/domain.c
> index 8efef5c..4f805d5 100644
> --- a/xen/common/domain.c
> +++ b/xen/common/domain.c
> @@ -110,6 +110,16 @@ static void vcpu_check_shutdown(struct vcpu *v)
>      spin_unlock(&d->shutdown_lock);
>  }
>  
> +static void vcpu_info_reset(struct vcpu *v)
> +{
> +    struct domain *d = v->domain;
> +
> +    v->vcpu_info = ((v->vcpu_id < XEN_LEGACY_MAX_VCPUS)
> +                    ? (vcpu_info_t *)&shared_info(d, vcpu_info[v->vcpu_id])
> +                    : &dummy_vcpu_info);
> +    v->vcpu_info_mfn = INVALID_MFN;
> +}

Great!
> +
>  struct vcpu *alloc_vcpu(
>      struct domain *d, unsigned int vcpu_id, unsigned int cpu_id)
>  {
> @@ -145,10 +155,7 @@ struct vcpu *alloc_vcpu(
>          v->runstate.state = RUNSTATE_offline;        
>          v->runstate.state_entry_time = NOW();
>          set_bit(_VPF_down, &v->pause_flags);
> -        v->vcpu_info = ((vcpu_id < XEN_LEGACY_MAX_VCPUS)
> -                        ? (vcpu_info_t *)&shared_info(d, vcpu_info[vcpu_id])
> -                        : &dummy_vcpu_info);
> -        v->vcpu_info_mfn = INVALID_MFN;
> +        vcpu_info_reset(v);
>          init_waitqueue_vcpu(v);
>      }
>  
> @@ -1010,6 +1017,29 @@ int domain_unpause_by_systemcontroller(struct domain *d)
>      return 0;
>  }
>  
> +int domain_soft_reset(struct domain *d)
> +{
> +    struct vcpu *v;
> +    int rc;
> +
> +    spin_lock(&d->shutdown_lock);
> +    for_each_vcpu ( d, v )
> +        if ( !v->paused_for_shutdown )
> +            return -EINVAL;

Ahem. You leave the spinlock still locked :-(

> +    spin_unlock(&d->shutdown_lock);
> +
> +    rc = evtchn_reset(d);
> +
> +    grant_table_warn_active_grants(d);
> +
> +    for_each_vcpu ( d, v )
> +        unmap_vcpu_info(v);
> +
> +    domain_resume(d);
> +
> +    return 0;
> +}