On 09.11.2020 14:16, Jürgen Groß wrote:
> On 09.11.20 12:58, Jan Beulich wrote:
>> On 09.11.2020 07:41, Juergen Gross wrote:
>>> --- a/xen/arch/x86/pv/shim.c
>>> +++ b/xen/arch/x86/pv/shim.c
>>> @@ -660,11 +660,12 @@ void pv_shim_inject_evtchn(unsigned int port)
>>> if ( port_is_valid(guest, port) )
>>> {
>>> struct evtchn *chn = evtchn_from_port(guest, port);
>>> - unsigned long flags;
>>>
>>> - spin_lock_irqsave(&chn->lock, flags);
>>> - evtchn_port_set_pending(guest, chn->notify_vcpu_id, chn);
>>> - spin_unlock_irqrestore(&chn->lock, flags);
>>> + if ( evtchn_read_trylock(chn) )
>>> + {
>>> + evtchn_port_set_pending(guest, chn->notify_vcpu_id, chn);
>>> + evtchn_read_unlock(chn);
>>> + }
>>
>> Does this need trylock?
>
> It is called directly from the event upcall, so interrupts should be
> off here. Without trylock this would result in check_lock() triggering.
Hmm, right. Since the trylock function needs exposing anyway, this
isn't much of a problem, the more that it fits the pattern of being
a send.
Jan
