On 2/27/2024 12:28 PM, Dave Jiang wrote:
On 2/27/24 1:24 PM, Jane Chu wrote:
On 2/27/2024 8:40 AM, Dave Jiang wrote:
On 2/26/24 10:32 PM, Cao, Quanquan/曹 全全 wrote:
Hi, Dave
On the basis of this patch, I conducted some tests and encountered unexpected
errors. I would like to inquire whether the design here is reasonable? Below
are the steps of my testing:
Link:
https://lore.kernel.org/linux-cxl/170138109724.2882696.123294980050048623.stgit@djiang5-mobl3/
Problem description: after creating a region, directly forcing 'disable-memdev'
and then consuming memory leads to a kernel panic.
If you are forcing memory disable when the memory cannot be offlined, then this
behavior is expected. You are ripping the memory away from underneath kernel
mm. The reason the check was added is to prevent the users from doing exactly
that.
Since user is doing the illegal thing, shouldn't that lead to SIGBUS or SIGKILL
?
The behavior is unpredictable once the CXL memory is ripped away. If the memory
only backed user memory then you may see SIGBUS. But if the memory backed
kernel data then kernel OOPs is not out of question.
Make sense, thanks for the clarification.
-jane
thanks,
-jane
Test environment:
KERNEL 6.8.0-rc1
QEMU 8.2.0-rc4
Test steps：
step1: set memory auto_online to movable zones.
echo online_movable > /sys/devices/system/memory/auto_online_blocks
step2: create region
cxl create-region -t ram -d decoder0.0 -m mem0
step3: disable memdev
cxl disable-memdev mem0 -f
step4: consum CXL memory
./consumemem <------kernel panic
numactl node status:
step1: numactl -H
available: 2 nodes (0-1)
node 0 cpus: 0 1
node 0 size: 968 MB
node 0 free: 664 MB
node 1 cpus: 2 3
node 1 size: 683 MB
node 1 free: 333 MB
node distances:
node 0 1
0: 10 20
step2: numactl -H
available: 3 nodes (0-2)
node 0 cpus: 0 1
node 0 size: 968 MB
node 0 free: 677 MB
node 1 cpus: 2 3
node 1 size: 683 MB
node 1 free: 333 MB
node 2 cpus:
node 2 size: 256 MB
node 2 free: 256 MB
node distances:
node 0 1 2
0: 10 20 20
1: 20 10 20
2: 20 20 10
step3: numactl -H
available: 3 nodes (0-2)
node 0 cpus: 0 1
node 0 size: 968 MB
node 0 free: 686 MB
node 1 cpus: 2 3
node 1 size: 683 MB
node 1 free: 336 MB
node 2 cpus:
node 2 size: 256 MB
node 2 free: 256 MB
node distances:
node 0 1 2
0: 10 20 20
1: 20 10 20
2: 20 20 10
