Re: rte_memzone_reserve and invalid socket id

[Tyler Retzlaff <roretzla@linux.microsoft.com>]

On Thu, Apr 14, 2022 at 10:03:10PM +0300, Dmitry Kozlyuk wrote:
> 2022-04-13 00:54 (UTC-0700), Tyler Retzlaff:
> > On Mon, Mar 28, 2022 at 11:04:36PM -0700, Tyler Retzlaff wrote:
> [...]
> > > 	memzone3 = rte_memzone_reserve(TEST_MEMZONE_NAME("testzone3"), 1000,
> > > 				1, 0);
> > >                                 ^ socket_id (to repeat just make it invalid)
> > > 
> > > the parameter documentation provided for reference.
> > > 
> > >  * @param socket_id
> > >  *   The socket identifier in the case of
> > >  *   NUMA. The value can be SOCKET_ID_ANY if there is no NUMA
> > >  *   constraint for the reserved zone.
> > > 
> > > of interest is should rte_memzone_reserve fail when provided a
> > > completely invalid socket_id?
> 
> I think it should.
> 
> > > 
> > > when running with --no-huge it does not because when --no-huge the
> > > socket_id no matter the value is silently re-mapped to SOCKET_ID_ANY
> > > though without --no-huge if a completely garbage socket_id were provided
> > > it seems the allocation would fail.
> 
> It's an implementation detail.
> NUMA could be respected for --no-huge if there was a need.
> 
> > > 
> > > so you get different behavior for an invalid socket_id depending on
> > > --no-huge vs with.
> > > 
> > > 	if (!rte_eal_has_hugepages() && socket_id < RTE_MAX_NUMA_NODES)
> > > 		socket_id = SOCKET_ID_ANY;
> > > 
> > > the test later fails at this check. where it compares the memzone3
> > > socket_id to what was used in the call to rte_memzone_reserve.
> > > 
> > > 	if (memzone3 != NULL && memzone3->socket_id != 1)
> > > 		return -1;                ^ SOCKET_ID_ANY if --no-huge
> > > 
> > > if the allocation had failed, the test would pass instead of failing at
> > > this point.
> > > 
> > > so what's wrong here? the test should be changed to expect different
> > > behavior with --no-huge vs huge or should rte_memzone_reserve be
> > > explicitly requiring SOCKET_ID_ANY instead of re-mapping invalid socket
> > > id?
> 
> memzone3->socket_id == SOCKET_ID_ANY should not be possible,
> because it's a specific selected socket ID.
> Rather, the check should be relaxed depending on rte_eal_has_hugepages().

okay, i think we are in agreement. my interpreted summary of how things
should be are as follows.

* rte_memzone_reserve() should fail if the provided socket_id is invalid
  for both huge and no-huge.

* the test of memzone3 should be conditional on rte_eal_has_hugepages()
  instead of allocation succcess/failure of memzone3.
  note: if this is corrected it would have masked the bug/difference
        in behavior.

* a separate test should exist that checks rte_memzone_reserve()
  correctly fails when given an invalid socket_id with both huge
  and no-huge.

if the 3 points above were to be addressed the issue is it is a
compatibility break. so while it should work a certain way the question
for the community now what should we do?

thanks