Re: [Xen-devel] [PATCH v8 05/11] xen: grant_table: implement grant_table_warn_active_grants()

[Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>]

Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> writes:

> On Tue, Jun 23, 2015 at 06:11:47PM +0200, Vitaly Kuznetsov wrote:
>> Log first 10 active grants of 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.
>
> Is there an particular reason 10 was choosen instead of 42 for example :-)
>

I was inpired by dump_pageframe_info() :-)

> Also the 10 should probably have an #define for it.
>

Ok, any preferred place/name for such define?

> Not sure I understand the usage case - except for development uses
> to report on the Xen console? But if that is the case why not
> use the 'g' on the ring console?

If there is a misbehaving backend and this cases the domain to crash
right after the soft reset 'g' option will not be available and it won't
be clear what caused the domain to crash.

>
>> 
>> Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
>> ---
>>  xen/common/grant_table.c      | 31 +++++++++++++++++++++++++++++++
>>  xen/include/xen/grant_table.h |  5 +++++
>>  2 files changed, 36 insertions(+)
>> 
>> diff --git a/xen/common/grant_table.c b/xen/common/grant_table.c
>> index db5e5db..c67db28 100644
>> --- a/xen/common/grant_table.c
>> +++ b/xen/common/grant_table.c
>> @@ -3309,6 +3309,37 @@ 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;
>> +
>> +    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 <= 10 )
>> +            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 > 10 )
>> +        printk(XENLOG_G_DEBUG "Dom%d has too many (%d) active grants"
>> +               " to report\n", d->domain_id, nr_active);
>> +
>> +    read_unlock(&gt->lock);
>> +}
>>  
>>  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(
>> -- 
>> 2.4.2
>> 

-- 
  Vitaly

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