Re: [PATCH v9 05/11] xen: grant_table: implement grant_table_warn_active_grants()

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

On Thu, Jul 16, 2015 at 06:27:20PM +0200, Vitaly Kuznetsov wrote:
> Log first 10 active grants for a domain. This function is going to be used
> for soft reset, active grants on this path usually mean misbehaving backends
> refusing to release their mappings on shutdown. We need that in addition to
> the already existent 'g' keyhandler as such misbehaving backends can cause a
> domain to crash right after the soft reset operation and 'g' option won't be
> available in this case.
> 
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>

Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> ---
> Changes since v8:
> - Use WARN_GRANT_MAX define instead of hardcoded 10 [Konrad Rzeszutek Wilk]
> - Update commit message explaining why 'g' keyhandler is not enough
>   [Konrad Rzeszutek Wilk]
> ---
>  xen/common/grant_table.c      | 35 +++++++++++++++++++++++++++++++++++
>  xen/include/xen/grant_table.h |  5 +++++
>  2 files changed, 40 insertions(+)
> 
> diff --git a/xen/common/grant_table.c b/xen/common/grant_table.c
> index 92f078e..c2e0210 100644
> --- a/xen/common/grant_table.c
> +++ b/xen/common/grant_table.c
> @@ -3348,6 +3348,41 @@ gnttab_release_mappings(
>      }
>  }
>  
> +void grant_table_warn_active_grants(struct domain *d)
> +{
> +    struct grant_table *gt = d->grant_table;
> +    struct active_grant_entry *act;
> +    grant_ref_t ref;
> +    unsigned int nr_active = 0;
> +
> +#define WARN_GRANT_MAX 10
> +
> +    read_lock(&gt->lock);
> +
> +    for ( ref = 0; ref != nr_grant_entries(gt); ref++ )
> +    {
> +        act = active_entry_acquire(gt, ref);
> +        if ( !act->pin )
> +        {
> +            active_entry_release(act);
> +            continue;
> +        }
> +
> +        nr_active++;
> +        if ( nr_active <= WARN_GRANT_MAX )
> +            printk(XENLOG_G_DEBUG "Dom%d has an active grant: GFN: %lx"
> +                   " (MFN: %lx)\n", d->domain_id, act->gfn, act->frame);
> +        active_entry_release(act);
> +    }
> +
> +    if ( nr_active > WARN_GRANT_MAX )
> +        printk(XENLOG_G_DEBUG "Dom%d has too many (%d) active grants"
> +               " to report\n", d->domain_id, nr_active);
> +
> +    read_unlock(&gt->lock);
> +
> +#undef WARN_GRANT_MAX
> +}
>  
>  void
>  grant_table_destroy(
> diff --git a/xen/include/xen/grant_table.h b/xen/include/xen/grant_table.h
> index 9c7b5a3..54005cc 100644
> --- a/xen/include/xen/grant_table.h
> +++ b/xen/include/xen/grant_table.h
> @@ -90,6 +90,11 @@ void grant_table_destroy(
>      struct domain *d);
>  void grant_table_init_vcpu(struct vcpu *v);
>  
> +/*
> + * Check if domain has active grants and log first 10 of them.
> + */
> +void grant_table_warn_active_grants(struct domain *d);
> +
>  /* Domain death release of granted mappings of other domains' memory. */
>  void
>  gnttab_release_mappings(
> -- 
> 2.4.3
>