The quilt patch titled
Subject: x86/mm: drop 4MB restriction on minimal NUMA node size
has been removed from the -mm tree. Its filename was
x86-mm-drop-4mb-restriction-on-minimal-numa-node-size.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
From: "Mike Rapoport (IBM)" <rppt@xxxxxxxxxx>
Subject: x86/mm: drop 4MB restriction on minimal NUMA node size
Date: Tue, 17 Oct 2023 09:22:15 +0300
Qi Zheng reports crashes in a production environment and provides a
simplified example as a reproducer:
For example, if we use qemu to start a two NUMA node kernel,
one of the nodes has 2M memory (less than NODE_MIN_SIZE),
and the other node has 2G, then we will encounter the
following panic:
[ 0.149844] BUG: kernel NULL pointer dereference, address: 0000000000000000
[ 0.150783] #PF: supervisor write access in kernel mode
[ 0.151488] #PF: error_code(0x0002) - not-present page
<...>
[ 0.156056] RIP: 0010:_raw_spin_lock_irqsave+0x22/0x40
<...>
[ 0.169781] Call Trace:
[ 0.170159] <TASK>
[ 0.170448] deactivate_slab+0x187/0x3c0
[ 0.171031] ? bootstrap+0x1b/0x10e
[ 0.171559] ? preempt_count_sub+0x9/0xa0
[ 0.172145] ? kmem_cache_alloc+0x12c/0x440
[ 0.172735] ? bootstrap+0x1b/0x10e
[ 0.173236] bootstrap+0x6b/0x10e
[ 0.173720] kmem_cache_init+0x10a/0x188
[ 0.174240] start_kernel+0x415/0x6ac
[ 0.174738] secondary_startup_64_no_verify+0xe0/0xeb
[ 0.175417] </TASK>
[ 0.175713] Modules linked in:
[ 0.176117] CR2: 0000000000000000
The crashes happen because of inconsistency between nodemask that has
nodes with less than 4MB as memoryless and the actual memory fed into
core mm.
The commit 9391a3f9c7f1 ("[PATCH] x86_64: Clear more state when ignoring
empty node in SRAT parsing") that introduced minimal size of a NUMA node
does not explain why a node size cannot be less than 4MB and what boot
failures this restriction might fix.
Since then a lot has changed and core mm won't confuse badly about small
node sizes.
Drop the limitation for the minimal node size.
Link: https://lkml.kernel.org/r/20231017062215.171670-1-rppt@xxxxxxxxxx
Signed-off-by: Mike Rapoport (IBM) <rppt@xxxxxxxxxx>
Reported-by: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
Closes: https://lore.kernel.org/all/20230212110305.93670-1-zhengqi.arch@xxxxxxxxxxxxx/
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Tested-by: Mario Casquero <mcasquer@xxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Peter Ziljstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/x86/include/asm/numa.h | 7 -------
arch/x86/mm/numa.c | 7 -------
2 files changed, 14 deletions(-)
--- a/arch/x86/include/asm/numa.h~x86-mm-drop-4mb-restriction-on-minimal-numa-node-size
+++ a/arch/x86/include/asm/numa.h
@@ -12,13 +12,6 @@
#define NR_NODE_MEMBLKS (MAX_NUMNODES*2)
-/*
- * Too small node sizes may confuse the VM badly. Usually they
- * result from BIOS bugs. So dont recognize nodes as standalone
- * NUMA entities that have less than this amount of RAM listed:
- */
-#define NODE_MIN_SIZE (4*1024*1024)
-
extern int numa_off;
/*
--- a/arch/x86/mm/numa.c~x86-mm-drop-4mb-restriction-on-minimal-numa-node-size
+++ a/arch/x86/mm/numa.c
@@ -601,13 +601,6 @@ static int __init numa_register_memblks(
if (start >= end)
continue;
- /*
- * Don't confuse VM with a node that doesn't have the
- * minimum amount of memory:
- */
- if (end && (end - start) < NODE_MIN_SIZE)
- continue;
-
alloc_node_data(nid);
}
_
Patches currently in -mm which might be from rppt@xxxxxxxxxx are
