diff mbox series

x86/mm: drop 4MB restriction on minimal NUMA node size

Message ID 20231017062215.171670-1-rppt@kernel.org
State New
Headers
Series x86/mm: drop 4MB restriction on minimal NUMA node size |

Commit Message

Mike Rapoport Oct. 17, 2023, 6:22 a.m. UTC 
  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(-)


base-commit: 94f6f0550c625fab1f373bb86a6669b45e9748b3

Comments

David Hildenbrand Oct. 17, 2023, 7:28 a.m. UTC | #1 
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?
David Hildenbrand Oct. 17, 2023, 7:35 a.m. UTC | #2 
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.
Mike Rapoport Oct. 17, 2023, 7:52 a.m. UTC | #3 
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
>
Mario Casquero Oct. 18, 2023, 11:55 a.m. UTC | #4 
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 mbox series

Patch

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);
 	}