STRUCT PANTHOR_VM_POOL(9)

okay bestie, welcome to the Kernel API Manual 💖 — today's main character is struct panthor_vm_pool(9), aka the VM pool object. It's giving kernel plumbing but make it cute. ✨

🦋 NAME 🦋

struct panthor_vm_pool — VM pool object. That's it, that's the name. No cap. 💅

✨ SYNOPSIS ✨

here's the struct in all its glory, copied exactly:

struct panthor_vm_pool {
    struct xarray xa;
    struct panthor_gem_object *dummy;
};

🫶 Members 🫶

okay so it has exactly two members, and they're both important:

• xa — the array used for VM handle tracking. It's the little index card system for VM handles, basically. 🗂️
• dummy — the dummy object used for sparse mappings. Yes, it's literally called dummy, and it's doing important work. 🙈

now the lore behind dummy: sparse bindings map virtual address ranges onto a dummy BO in a modulo fashion. Sparse writes are meant to be discarded, and sparse reads are undefined — but those writes are still reflected in the dummy buffer. So we have to keep a dummy object per file context, or data leaks between them. That's the whole reason it exists. Periodt. 🫶

🚨 bestie, this is the caveat: one dummy object per file context, not shared, because sharing it would leak data between contexts. Not the vibe. 💀

💜 SEE ALSO 💜

the kernel file is ./drivers/gpu/drm/panthor/panthor_mmu.c, and here's the whole friend group:

• struct panthor_as_slot(9)
• struct panthor_mmu(9)
• struct panthor_vma(9)
• struct panthor_vm_op_ctx(9)
• struct panthor_vm(9)
• struct panthor_vm_bind_job(9)
• alloc_pt(9)
• free_pt(9)
• panthor_vm_has_unhandled_faults(9)
• panthor_vm_is_unusable(9)
• panthor_vm_active(9)
• panthor_vm_idle(9)
• panthor_vm_as(9)
• panthor_vm_alloc_va(9)
• panthor_vm_free_va(9)
• panthor_vm_get_bo_for_va(9)
• panthor_vm_pool_create_vm(9)
• panthor_vm_pool_destroy_vm(9)
• panthor_vm_pool_get_vm(9)
• panthor_vm_pool_destroy(9)
• panthor_vm_pool_create(9)
• panthor_mmu_suspend(9)
• panthor_mmu_resume(9)
• panthor_mmu_pre_reset(9)
• panthor_mmu_post_reset(9)
• panthor_vm_put(9)
• panthor_vm_get(9)
• panthor_vm_get_heap_pool(9)
• panthor_vm_heaps_sizes(9)
• panthor_vm_resv(9)
• panthor_vm_bind_job_put(9)
• panthor_vm_create(9)
• panthor_vm_bind_job_create(9)
• panthor_vm_bind_job_prepare_resvs(9)
• panthor_vm_bind_job_update_resvs(9)
• panthor_vm_bind_exec_sync_op(9)
• panthor_vm_map_bo_range(9)
• panthor_vm_unmap_range(9)
• panthor_vm_prepare_mapped_bos_resvs(9)
• panthor_mmu_unplug(9)
• panthor_mmu_init(9)
• panthor_mmu_debugfs_init(9)
• panthor_mmu_pt_cache_init(9)
• panthor_mmu_pt_cache_fini(9)

xoxo, source/version ./drivers/gpu/drm/panthor, dated October 2026, and this whole page is struct panthor_vm_pool(9) 💖✨