Re: [Xen-devel] [PATCH v2 1/1] evtchn: make EVTCHNOP_reset suitable for kexec

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 30.07.14 at 15:42, <david.vrabel@xxxxxxxxxx> wrote:
> On 30/07/14 14:26, Vitaly Kuznetsov wrote:
>> --- a/xen/common/event_channel.c
>> +++ b/xen/common/event_channel.c
>> @@ -957,6 +957,17 @@ static long evtchn_reset(evtchn_reset_t *r)
>>      for ( i = 0; port_is_valid(d, i); i++ )
>>          (void)__evtchn_close(d, i);
>>  
>> +    if ( (d == current->domain) && d->evtchn_fifo )
>> +    {
>> +        /*
>> +         * Guest domain called EVTCHNOP_reset with DOMID_SELF, destroying
>> +         * FIFO event array and control blocks, resetting evtchn_port_ops to
>> +         * evtchn_port_ops_2l.
>> +         */
>> +        evtchn_fifo_destroy(d);
>> +        evtchn_2l_init(d);
> 
> You need to take d->event_lock around this if, or the guest could try to
> bind another event whilst the ABI is in an inconsistent state.

True, but then not just around this. Subsequent to any of the
__evtchn_close() invocations above, a port could also get
re-used (resulting in at least leaks). So I guess after taking the
lock there would also need to be a loop checking that all ports
are still closed (and return an error if they aren't).

Jan


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