Re: [RFC PATCH 2/3] dma-buf: add a warn-only mode to DMABUF_DEBUG

["Christian König" <christian.koenig@amd.com>]

On 10/9/26 14:53, Jason Gunthorpe wrote:
> On Wed, Oct 07, 2026 at 02:02:31PM +0200, Diederik de Haas wrote:
>> [ 1091.981354] rc rc3: two consecutive events of type space
>> [ 1104.670513] input: EDIFIER e235 (AVRCP) as /devices/virtual/input/input12
>> [ 1172.090231] devfreq fb000000.gpu: Couldn't update frequency transition information.
>> [ 1189.403278] devfreq fb000000.gpu: Couldn't update frequency transition information.
>> [ 1206.309295] input: EDIFIER e235 (AVRCP) as /devices/virtual/input/input13
>> [ 1268.968696] DMA-BUF: importer used the CPU side of an exporter's sg_table
> 
> This is a nice stack trace, is that the point of this series?
> 
>> [ 1268.968710] CPU: 6 UID: 1000 PID: 29025 Comm: sway Not tainted 7.3-rc6+unreleased-arm64-cknow #1 PREEMPTLAZY  Debian 7.3~rc6-3
>> [ 1268.968715] Hardware name: FriendlyElec NanoPC-T6 Plus (DT)
>> [ 1268.968717] Call trace:
>> [ 1268.968719]  show_stack+0x20/0x38 (C)
>> [ 1268.968726]  dump_stack_lvl+0x60/0x80
>> [ 1268.968730]  sg_dmabuf_cpu_access_warn.part.0+0x24/0x30
>> [ 1268.968734]  sg_dmabuf_cpu_access_warn+0x34/0x38
>> [ 1268.968739]  iommu_map_sg+0xc8/0x1e0
>> [ 1268.968745]  rockchip_gem_iommu_map+0x8c/0x128 [rockchipdrm]
>> [ 1268.968757]  rockchip_gem_prime_import_sg_table+0x58/0x160 [rockchipdrm]
>> [ 1268.968761]  drm_gem_prime_import_dev+0xa8/0x1d0 [drm]
>> [ 1268.968776]  drm_gem_prime_fd_to_handle+0x1a4/0x280 [drm]
> 
> So.. This is the exact same thing I need for iommufd.
> 
> rockchip is managing its own iommu domain and you cannot map to an
> iommu domain without using a physical address.
> 
> Of course it is *completely* illegal to call iommu_map_sgtable() in the
> importer side of a dmabuf.

Yeah we are deprecating this for the last ~5 years now. This bubbled up because I change to DMA-buf debug code to be enabled by default on DEBUG_KERNEL.

Rob is now working on a solution right now for MSM which should be used for rockchip as well.

Regards,
Christian.

> 
> static int rockchip_gem_iommu_map(struct rockchip_gem_object *rk_obj)
> {
> [..]
> 	ret = iommu_map_sgtable(private->domain, rk_obj->dma_addr, rk_obj->sgt,
> 				prot);
> 
> Jason