Re: port-amd64/60920: 11.0 kernel for amd64 fails with null pointer deref in uvm_page_redim()

["Michael van Elst via gnats" <gnats-admin%NetBSD.org@localhost>]

The following reply was made to PR port-amd64/60920; it has been noted by GNATS.

From: mlelstv%serpens.de@localhost (Michael van Elst)
To: gnats-bugs%netbsd.org@localhost
Cc: 
Subject: Re: port-amd64/60920: 11.0 kernel for amd64 fails with null pointer deref in uvm_page_redim()
Date: Sat, 24 Oct 2026 23:43:33 -0000 (UTC)

 he%NetBSD.org@localhost (Havard Eidnes) writes:
 
 >>  >So bucketcount = 2, at least in 10.0?
 >>
 >>  bucketcount = 2 is a problem if the code touches bucket 2
 >>  (only 0 + 1 exist).
 
 >Well, there's a difference between "index" and "count"; one would
 >say that one has 2 buckets if they're indexed with 0 and 1, no?
 
 >If uvm.bucketcount = newnbuckets = 2, (whatever % newnbuckets)
 >will be either 0 or 1, no?  So are we getting to the crash via
 
 >                      if (uvm_page_numa_region != NULL) {
 >                              nb = uvm_page_numa_lookup(pg);
 
 >?
 
 
 Either that, or the code is miscompiled.
 
 
 >I'll note that I don't quite understand why the last 4 cores are
 >noted as "node 1" whereas the 4 first in the last package are
 >"node 0", in
 
 You have two packages, each made out of two dies, each die
 has 4 cores and an L3 cache. That's the 4 NUMA nodes.