qemu-devel
[Top][All Lists]
Advanced
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [PATCH] hw/arm/virt: Prevent CPUs in one socket to span mutiple NUMA

From: Philippe Mathieu-Daudé
Subject: Re: [PATCH] hw/arm/virt: Prevent CPUs in one socket to span mutiple NUMA nodes
Date: Wed, 22 Feb 2023 00:31:38 +0100
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.8.0 
On 22/2/23 00:12, Gavin Shan wrote:

On 2/21/23 9:21 PM, Philippe Mathieu-Daudé wrote:

On 21/2/23 10:21, Gavin Shan wrote:

On 2/21/23 8:15 PM, Philippe Mathieu-Daudé wrote:

On 21/2/23 09:53, Gavin Shan wrote:

Linux kernel guest reports warning when two CPUs in one socket have
been associated with different NUMA nodes, using the following command
lines.

   -smp 6,maxcpus=6,sockets=2,clusters=1,cores=3,threads=1 \
   -numa node,nodeid=0,cpus=0-1,memdev=ram0                \
   -numa node,nodeid=1,cpus=2-3,memdev=ram1                \
   -numa node,nodeid=2,cpus=4-5,memdev=ram2                \

   ------------[ cut here ]------------
   WARNING: CPU: 0 PID: 1 at kernel/sched/topology.c:2271 build_sched_domains+0x284/0x910 
   Modules linked in:
   CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.14.0-268.el9.aarch64 #1
   pstate: 00400005 (nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
   pc : build_sched_domains+0x284/0x910
   lr : build_sched_domains+0x184/0x910
   sp : ffff80000804bd50
   x29: ffff80000804bd50 x28: 0000000000000002 x27: 0000000000000000
   x26: ffff800009cf9a80 x25: 0000000000000000 x24: ffff800009cbf840
   x23: ffff000080325000 x22: ffff0000005df800 x21: ffff80000a4ce508
   x20: 0000000000000000 x19: ffff000080324440 x18: 0000000000000014
   x17: 00000000388925c0 x16: 000000005386a066 x15: 000000009c10cc2e
   x14: 00000000000001c0 x13: 0000000000000001 x12: ffff00007fffb1a0
   x11: ffff00007fffb180 x10: ffff80000a4ce508 x9 : 0000000000000041
   x8 : ffff80000a4ce500 x7 : ffff80000a4cf920 x6 : 0000000000000001
   x5 : 0000000000000001 x4 : 0000000000000007 x3 : 0000000000000002
   x2 : 0000000000001000 x1 : ffff80000a4cf928 x0 : 0000000000000001
   Call trace:
    build_sched_domains+0x284/0x910
    sched_init_domains+0xac/0xe0
    sched_init_smp+0x48/0xc8
    kernel_init_freeable+0x140/0x1ac
    kernel_init+0x28/0x140
    ret_from_fork+0x10/0x20

Fix it by preventing mutiple CPUs in one socket to be associated with
different NUMA nodes.

Reported-by: Yihuang Yu <yihyu@redhat.com>
Signed-off-by: Gavin Shan <gshan@redhat.com>
---
  hw/arm/virt.c | 37 +++++++++++++++++++++++++++++++++++++
  1 file changed, 37 insertions(+)

diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index ac626b3bef..e0af267c77 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -230,6 +230,39 @@ static bool cpu_type_valid(const char *cpu)
      return false;
  }
+static bool numa_state_valid(MachineState *ms)
+{
+    MachineClass *mc = MACHINE_GET_CLASS(ms);
+    NumaState *state = ms->numa_state;
+    const CPUArchIdList *possible_cpus = mc->possible_cpu_arch_ids(ms); 
+    const CPUArchId *cpus = possible_cpus->cpus;
+    int len = possible_cpus->len, i, j;
+
+    if (!state || state->num_nodes <= 1 || len <= 1) {
+        return true;
+    }
+
+    for (i = 0; i < len; i++) {
+        for (j = i + 1; j < len; j++) {
+            if (cpus[i].props.has_socket_id &&
+                cpus[i].props.has_node_id &&
+                cpus[j].props.has_socket_id &&
+                cpus[j].props.has_node_id &&
+                cpus[i].props.socket_id == cpus[j].props.socket_id &&
+                cpus[i].props.node_id != cpus[j].props.node_id) {
+                error_report("CPU-%d and CPU-%d in socket-%ld have been " 
+                             "associated with node-%ld and node-%ld",
+                             i, j, cpus[i].props.socket_id,
+                             cpus[i].props.node_id,
+                             cpus[j].props.node_id);
+                return false;
+            }
+        }
+    }
+
+    return true;
+}
+
  static void create_randomness(MachineState *ms, const char *node)
  {
      struct {
@@ -2040,6 +2073,10 @@ static void machvirt_init(MachineState *machine) 
          exit(1);
      }
+    if (!numa_state_valid(machine)) {
+        exit(1);
+    }


Why restrict to the virt machine?
We tried x86 machines and virt machine, but the issue isn't reproducible on x86 machines. So I think it's machine or architecture specific issue. However, I believe RiscV should have similar issue because linux/drivers/base/arch_topology.c is shared by ARM64 and RiscV. 
x86 doesn't use the driver to populate its CPU topology.


Oh, I haven't thought about the other archs, I meant this seem a generic
issue which affects all (ARM) machines, so why restrict to the (ARM)
virt machine?



[Ccing Igor for comments]
Well, virt machine is the only concern to us for now. You're right that all ARM64 and ARM machines need this check and limitation. So the check needs to be done in the generic path. The best way I can figure out is like something below. The idea is to introduce a switch to 'struct NumaState' and do the check in the generic path. The switch is turned on by individual machines. Please let me 
know if you have better ideas


Can't this be done generically in machine_numa_finish_cpu_init()
-> numa_validate_initiator()?
- Add 'bool struct NumaState::has_strict_socket_mapping', which is 'false' by default until   machine specific initialization function calls helper set_numa_strict_socket_mapping(), for 
   example in hw/arm/virt.c::virt_instance_init().
- In numa_complete_configuration(), do the check to make sure the socket doesn't cross over   the NUMA node boundary if 'bool struct NumaState::has_strict_socket_mapping' is true. 

Thanks,
Gavin
reply via email to
[Prev in Thread] Current Thread [Next in Thread]