On Tue, Mar 03, 2026 at 09:51:58AM +0800, Kai Huang wrote: > Increase 'maxnode' when using 'get_mempolicy' syscall in guest_memfd > mmap and NUMA policy tests to fix a failure on one Intel GNR platform. > > On a CXL-capable platform, the memory affinity of CXL memory regions may > not be covered by the SRAT. Since each CXL memory region is enumerated > via a CFMWS table, at early boot the kernel parses all CFMWS tables to > detect all CXL memory regions and assigns a 'faked' NUMA node for each > of them, starting from the highest NUMA node ID enumerated via the SRAT. > > This increases the 'nr_node_ids'. E.g., on the aforementioned Intel GNR > platform which has 4 NUMA nodes and 18 CFMWS tables, it increases to 22. > > This results in the 'get_mempolicy' syscall failure on that platform, > because currently 'maxnode' is hard-coded to 8 but the 'get_mempolicy' > syscall requires the 'maxnode' to be not smaller than the 'nr_node_ids'. > > Increase the 'maxnode' to the number of bits of 'nodemask', which is > 'unsigned long', to fix this. > > This may not cover all systems. Perhaps a better way is to always set > the 'nodemask' and 'maxnode' based on the actual maximum NUMA node ID on > the system, but for now just do the simple way.
Reviewed-by: Yuan Yao <[email protected]> > > Reported-by: Yi Lai <[email protected]> > Closes: https://bugzilla.kernel.org/show_bug.cgi?id=221014 > Closes: > https://lore.kernel.org/all/[email protected]%2F > Signed-off-by: Kai Huang <[email protected]> > --- > > v1 -> v2: > - Add 'Reported-by' and 'Closes" tags. - Sean > - Use BITS_PER_TYPE(). - Sean > - Slightly simplify changelog to simply say "increase 'maxnode' to bits > of 'nodemask'" to reflect the code better. > > --- > tools/testing/selftests/kvm/guest_memfd_test.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/tools/testing/selftests/kvm/guest_memfd_test.c > b/tools/testing/selftests/kvm/guest_memfd_test.c > index 618c937f3c90..cc329b57ce2e 100644 > --- a/tools/testing/selftests/kvm/guest_memfd_test.c > +++ b/tools/testing/selftests/kvm/guest_memfd_test.c > @@ -80,7 +80,7 @@ static void test_mbind(int fd, size_t total_size) > { > const unsigned long nodemask_0 = 1; /* nid: 0 */ > unsigned long nodemask = 0; > - unsigned long maxnode = 8; > + unsigned long maxnode = BITS_PER_TYPE(nodemask); > int policy; > char *mem; > int ret; > > base-commit: a91cc48246605af9aeef1edd32232976d74d9502 > -- > 2.53.0 >
