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

[Jason Gunthorpe <jgg@nvidia.com>]

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.

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