On 06.09.2022 15:40, Rahul Singh wrote: > From: Julien Grall <[email protected]> > > Since commit 01280dc19cf3 "evtchn: simplify port_is_valid()", the event > channels code assumes that all the buckets below d->valid_evtchns are > always allocated. > > This assumption hold in most of the situation because a guest is not > allowed to chose the port. Instead, it will be the first free from port > 0. > > When static event channel support will be added for dom0less domains > user can request to allocate the evtchn port numbers that are scattered > in nature. > > The existing implementation of evtchn_allocate_port() is not able to > deal with such situation and will end up to override bucket or/and leave > some bucket unallocated. The latter will result to a droplet crash if > the event channel belongs to an unallocated bucket. > > This can be solved by making sure that all the buckets below > d->valid_evtchns are allocated. There should be no impact for most of > the situation but LM/LU as only one bucket would be allocated. For > LM/LU, we may end up to allocate multiple buckets if ports in use are > sparse. > > A potential alternative is to check that the bucket is valid in > is_port_valid(). This should still possible to do it without taking > per-domain lock but will result a couple more of memory access. > > Signed-off-by: Julien Grall <[email protected]> > Signed-off-by: Rahul Singh <[email protected]> > Reviewed-by: Michal Orzel <[email protected]>
Reviewed-by: Jan Beulich <[email protected]>
