[PATCH v5 07/14] drm/panthor: Add the MMU/VM logical block

[Steven Price]

On 18/02/2024 21:41, Boris Brezillon wrote:
> MMU and VM management is related and placed in the same source file.
> 
> Page table updates are delegated to the io-pgtable-arm driver that's in
> the iommu subsystem.
> 
> The VM management logic is based on drm_gpuva_mgr, and is assuming the
> VA space is mostly managed by the usermode driver, except for a reserved
> portion of this VA-space that's used for kernel objects (like the heap
> contexts/chunks).
> 
> Both asynchronous and synchronous VM operations are supported, and
> internal helpers are exposed to allow other logical blocks to map their
> buffers in the GPU VA space.
> 
> There's one VM_BIND queue per-VM (meaning the Vulkan driver can only
> expose one sparse-binding queue), and this bind queue is managed with
> a 1:1 drm_sched_entity:drm_gpu_scheduler, such that each VM gets its own
> independent execution queue, avoiding VM operation serialization at the
> device level (things are still serialized at the VM level).
> 
> The rest is just implementation details that are hopefully well explained
> in the documentation.
> 
> v5:
> - Fix a double panthor_vm_cleanup_op_ctx() call
> - Fix a race between panthor_vm_prepare_map_op_ctx() and
>   panthor_vm_bo_put()
> - Fix panthor_vm_pool_destroy_vm() kernel doc
> - Fix paddr adjustment in panthor_vm_map_pages()
> - Fix bo_offset calculation in panthor_vm_get_bo_for_va()
> 
> v4:
> - Add an helper to return the VM state
> - Check drmm_mutex_init() return code
> - Remove the VM from the AS reclaim list when panthor_vm_active() is
>   called
> - Count the number of active VM users instead of considering there's
>   at most one user (several scheduling groups can point to the same
>   vM)
> - Pre-allocate a VMA object for unmap operations (unmaps can trigger
>   a sm_step_remap() call)
> - Check vm->root_page_table instead of vm->pgtbl_ops to detect if
>   the io-pgtable is trying to allocate the root page table
> - Don't memset() the va_node in panthor_vm_alloc_va(), make it a
>   caller requirement
> - Fix the kernel doc in a few places
> - Drop the panthor_vm::base offset constraint and modify
>   panthor_vm_put() to explicitly check for a NULL value
> - Fix unbalanced vm_bo refcount in panthor_gpuva_sm_step_remap()
> - Drop stale comments about the shared_bos list
> - Patch mmu_features::va_bits on 32-bit builds to reflect the
>   io_pgtable limitation and let the UMD know about it
> 
> v3:
> - Add acks for the MIT/GPL2 relicensing
> - Propagate MMU faults to the scheduler
> - Move pages pinning/unpinning out of the dma_signalling path
> - Fix 32-bit support
> - Rework the user/kernel VA range calculation
> - Make the auto-VA range explicit (auto-VA range doesn't cover the full
>   kernel-VA range on the MCU VM)
> - Let callers of panthor_vm_alloc_va() allocate the drm_mm_node
>   (embedded in panthor_kernel_bo now)
> - Adjust things to match the latest drm_gpuvm changes (extobj tracking,
>   resv prep and more)
> - Drop the per-AS lock and use slots_lock (fixes a race on vm->as.id)
> - Set as.id to -1 when reusing an address space from the LRU list
> - Drop misleading comment about page faults
> - Remove check for irq being assigned in panthor_mmu_unplug()
> 
> Co-developed-by: Steven Price <steven.price at arm.com>
> Signed-off-by: Steven Price <steven.price at arm.com>
> Signed-off-by: Boris Brezillon <boris.brezillon at collabora.com>
> Acked-by: Steven Price <steven.price at arm.com> # MIT+GPL2 relicensing,Arm
> Acked-by: Grant Likely <grant.likely at linaro.org> # MIT+GPL2 relicensing,Linaro
> Acked-by: Boris Brezillon <boris.brezillon at collabora.com> # MIT+GPL2 relicensing,Collabora

LGTM

Reviewed-by: Steven Price <steven.price at arm.com>

Thanks,

Stev