| Message ID | 20231017062215.171670-1-rppt@kernel.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | x86/mm: drop 4MB restriction on minimal NUMA node size | expand |
On 17.10.23 08:22, Mike Rapoport wrote: > From: "Mike Rapoport (IBM)" <rppt@kernel.org> > > 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. > > Reported-by: Qi Zheng <zhengqi.arch@bytedance.com> > Signed-off-by: Mike Rapoport (IBM) <rppt@kernel.org> > Acked-by: David Hildenbrand <david@redhat.com> > Acked-by: Michal Hocko <mhocko@suse.com> > Link: https://lore.kernel.org/all/20230212110305.93670-1-zhengqi.arch@bytedance.com/ That's just a resend I assume? Or has anything changed?
On 17.10.23 09:28, David Hildenbrand wrote: > On 17.10.23 08:22, Mike Rapoport wrote: >> From: "Mike Rapoport (IBM)" <rppt@kernel.org> >> >> 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. >> >> Reported-by: Qi Zheng <zhengqi.arch@bytedance.com> >> Signed-off-by: Mike Rapoport (IBM) <rppt@kernel.org> >> Acked-by: David Hildenbrand <david@redhat.com> >> Acked-by: Michal Hocko <mhocko@suse.com> >> Link: https://lore.kernel.org/all/20230212110305.93670-1-zhengqi.arch@bytedance.com/ > > That's just a resend I assume? Or has anything changed? Saw the other mail now, so just a resend.
On Tue, Oct 17, 2023 at 09:28:14AM +0200, David Hildenbrand wrote: > On 17.10.23 08:22, Mike Rapoport wrote: > > From: "Mike Rapoport (IBM)" <rppt@kernel.org> > > > > 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. > > > > Reported-by: Qi Zheng <zhengqi.arch@bytedance.com> > > Signed-off-by: Mike Rapoport (IBM) <rppt@kernel.org> > > Acked-by: David Hildenbrand <david@redhat.com> > > Acked-by: Michal Hocko <mhocko@suse.com> > > Link: https://lore.kernel.org/all/20230212110305.93670-1-zhengqi.arch@bytedance.com/ > > That's just a resend I assume? Or has anything changed? Oh, I forgot RESEND prefix, sorry > -- > Cheers, > > David / dhildenb >
This patch has been successfully tested by QE. Start a VM with two NUMA nodes, one of them with less than 2M of memory. Check there is no kernel panic and the VM boots up smoothly. Tested-by: Mario Casquero <mcasquer@redhat.com> BR, Mario On Tue, Oct 17, 2023 at 8:24 AM Mike Rapoport <rppt@kernel.org> wrote: > > From: "Mike Rapoport (IBM)" <rppt@kernel.org> > > 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. > > Reported-by: Qi Zheng <zhengqi.arch@bytedance.com> > Signed-off-by: Mike Rapoport (IBM) <rppt@kernel.org> > Acked-by: David Hildenbrand <david@redhat.com> > Acked-by: Michal Hocko <mhocko@suse.com> > Link: https://lore.kernel.org/all/20230212110305.93670-1-zhengqi.arch@bytedance.com/ > --- > arch/x86/include/asm/numa.h | 7 ------- > arch/x86/mm/numa.c | 7 ------- > 2 files changed, 14 deletions(-) > > diff --git a/arch/x86/include/asm/numa.h b/arch/x86/include/asm/numa.h > index e3bae2b60a0d..ef2844d69173 100644 > --- a/arch/x86/include/asm/numa.h > +++ b/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; > > /* > diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c > index 2aadb2019b4f..55e3d895f15c 100644 > --- a/arch/x86/mm/numa.c > +++ b/arch/x86/mm/numa.c > @@ -601,13 +601,6 @@ static int __init numa_register_memblks(struct numa_meminfo *mi) > 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); > } > > > base-commit: 94f6f0550c625fab1f373bb86a6669b45e9748b3 > -- > 2.39.2 >
diff --git a/arch/x86/include/asm/numa.h b/arch/x86/include/asm/numa.h index e3bae2b60a0d..ef2844d69173 100644 --- a/arch/x86/include/asm/numa.h +++ b/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; /* diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c index 2aadb2019b4f..55e3d895f15c 100644 --- a/arch/x86/mm/numa.c +++ b/arch/x86/mm/numa.c @@ -601,13 +601,6 @@ static int __init numa_register_memblks(struct numa_meminfo *mi) 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); }