On Thu, Feb 22, 2024 at 05:33:48PM +0100, Marco Pagani wrote:

...

In this context, the TTM unit tests fail as well in qemu, with worse result: It seems there is some bad cleanup after a failed test case, causing list corruptions in the drm core and ultimately a crash. I don't know if this is also caused by the missing dma_mask initialization.

That's interesting. Which --arch argument are you using to run the tests with QEMU?

Example (I am not sure if any of those parameters matters; it is just one of my tests):

qemu-system-x86_64 -kernel arch/x86/boot/bzImage -M q35 -cpu IvyBridge \ -no-reboot -snapshot -smp 2 \ -device e1000,netdev=net0 -netdev user,id=net0 -m 512 \ -drive file=rootfs.ext2,format=raw,if=ide \ --append "earlycon=uart8250,io,0x3f8,9600n8 root=/dev/sda1 console=ttyS0" \ -d unimp,guest_errors -nographic -monitor none

This results in:

[ ... ] [ 5.989496] KTAP version 1 [ 5.989639] # Subtest: ttm_device [ 5.989711] # module: ttm_device_test [ 5.989760] 1..5 [ 6.002044] ok 1 ttm_device_init_basic [ 6.013557] ok 2 ttm_device_init_multiple ILLOPC: ffffffffb8ac9350: 0f 0b [ 6.022481] ok 3 ttm_device_fini_basic [ 6.026172] ------------[ cut here ]------------ [ 6.026315] WARNING: CPU: 1 PID: 1575 at drivers/gpu/drm/ttm/ttm_device.c:206 ttm_device_init+0x170/0x190 ... [ 6.135016] ok 3 Above the allocation limit [ 6.138759] ------------[ cut here ]------------ [ 6.138925] WARNING: CPU: 1 PID: 1595 at kernel/dma/mapping.c:503 dma_alloc_attrs+0xf6/0x100 ... [ 6.143850] # ttm_pool_alloc_basic: ASSERTION FAILED at drivers/gpu/drm/ttm/tests/ttm_pool_test.c:162 [ 6.143850] Expected err == 0, but [ 6.143850] err == -12 (0xfffffffffffffff4) [ 6.148824] not ok 4 One page, with coherent DMA mappings enabled

From there things go downhill.

[ 6.152821] list_add corruption. prev->next should be next (ffffffffbbd53950), but was 0000000000000000. (prev=ffff8af1c38f9e20).

and so on until the emulation crashes.

Guenter