Hi Christian, I read amdgpu_ttm_io_mem_reserve() and amdgpu_ttm_io_mem_free() and relevant codes from amdgpu_vram_scratch_init and amdgpu_vram_scratch_fini. No. For the current source code, I think the premap and no-op is not working. I add printk to prove. You can see bo_kmap_type is an invalid value. ioremap_wc is really called to map the IO range into vmalloc space. ... Apr 20 16:31:18 axie-System-Product-Name kernel: [ 106.759623] entering amdgpu_vram_scratch_init. Apr 20 16:31:18 axie-System-Product-Name kernel: [ 106.759631] scratch ioremap_wc Apr 20 16:31:18 axie-System-Product-Name kernel: [ 106.759631] bo_kmap_type = 129 Apr 20 16:31:18 axie-System-Product-Name kernel: [ 106.759632] bus address = (null) Apr 20 16:31:18 axie-System-Product-Name kernel: [ 106.759632] is_iomem = 1 Apr 20 16:31:18 axie-System-Product-Name kernel: [ 106.759633] leaving amdgpu_vram_scratch_init. ... I don't have log on rmmod AMDGPU yet. There are quite some settings to make that happen in my computer. I think they are symemtric. Both mapping and unmapping are not no-op. Here is the printk patch for your reference.
