Re: [PATCH v2 06/15] drm/panthor: Add GEM logical block

From: Steven Price <steven.price@arm.com>
To: Boris Brezillon <boris.brezillon@collabora.com>,
	dri-devel@lists.freedesktop.org
Cc: "Nicolas Boichat" <drinkcat@chromium.org>,
	"Daniel Stone" <daniels@collabora.com>,
	"Neil Armstrong" <neil.armstrong@linaro.org>,
	"Liviu Dudau" <Liviu.Dudau@arm.com>,
	"Clément Péron" <peron.clem@gmail.com>,
	"Marty E . Plummer" <hanetzer@startmail.com>,
	"Robin Murphy" <robin.murphy@arm.com>,
	"Faith Ekstrand" <faith.ekstrand@collabora.com>
Subject: Re: [PATCH v2 06/15] drm/panthor: Add GEM logical block
Date: Mon, 14 Aug 2023 14:40:25 +0100	[thread overview]
Message-ID: <1ae8e22b-c9f2-aa93-dc39-b25cd3adbfda@arm.com> (raw)
In-Reply-To: <20230809165330.2451699-7-boris.brezillon@collabora.com>

On 09/08/2023 17:53, Boris Brezillon wrote:
> Anything relating to GEM object management is placed here. Nothing
> particularly interesting here, given the implementation is based on
> drm_gem_shmem_object, which is doing most of the work.
> 
> v2:
> - Rename the driver (pancsf -> panthor)
> - Change the license (GPL2 -> MIT + GPL2)
> - Split the driver addition commit
> - Document the code
> 
> Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>

One minor comment below, but otherwise:

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

> ---
>  drivers/gpu/drm/panthor/panthor_gem.c | 229 ++++++++++++++++++++++++++
>  drivers/gpu/drm/panthor/panthor_gem.h |  96 +++++++++++
>  2 files changed, 325 insertions(+)
>  create mode 100644 drivers/gpu/drm/panthor/panthor_gem.c
>  create mode 100644 drivers/gpu/drm/panthor/panthor_gem.h
> 
> diff --git a/drivers/gpu/drm/panthor/panthor_gem.c b/drivers/gpu/drm/panthor/panthor_gem.c
> new file mode 100644
> index 000000000000..a441a68822ca
> --- /dev/null
> +++ b/drivers/gpu/drm/panthor/panthor_gem.c
> @@ -0,0 +1,229 @@
> +// SPDX-License-Identifier: GPL-2.0 or MIT
> +/* Copyright 2019 Linaro, Ltd, Rob Herring <robh@kernel.org> */
> +/* Copyright 2023 Collabora ltd. */
> +
> +#include <linux/err.h>
> +#include <linux/slab.h>
> +#include <linux/dma-buf.h>
> +#include <linux/dma-mapping.h>
> +
> +#include <drm/panthor_drm.h>
> +
> +#include "panthor_device.h"
> +#include "panthor_gem.h"
> +#include "panthor_mmu.h"
> +
> +static void panthor_gem_free_object(struct drm_gem_object *obj)
> +{
> +	struct panthor_gem_object *bo = to_panthor_bo(obj);
> +
> +	if (drm_WARN_ON(obj->dev, bo->va_node))
> +		panthor_vm_free_va(bo->exclusive_vm, bo->va_node);
> +
> +	panthor_vm_put(bo->exclusive_vm);
> +	drm_gem_free_mmap_offset(&bo->base.base);
> +	mutex_destroy(&bo->gpuva_list_lock);
> +	drm_gem_shmem_free(&bo->base);
> +}
> +
> +/**
> + * panthor_gem_unmap_and_put() - Unmap and drop the reference on a GEM object
> + * @vm: VM to unmap the GEM from.
> + * @bo: GEM object to unmap/release.
> + * @gpu_va: GPU/MCU virtual address the GEM object was mapped at.
> + * @cpu_va: kernel mapping of the GEM object.
> + * Can be NULL if the GEM was not CPU mapped.
> + *
> + * Should be called to undo what was done in panthor_gem_create_and_map().
> + */
> +void panthor_gem_unmap_and_put(struct panthor_vm *vm,
> +			       struct panthor_gem_object *bo,
> +			       u64 gpu_va, void *cpu_va)
> +{
> +	if (cpu_va) {
> +		struct iosys_map map = IOSYS_MAP_INIT_VADDR(cpu_va);
> +
> +		drm_gem_vunmap_unlocked(&bo->base.base, &map);
> +	}
> +
> +	drm_WARN_ON(bo->base.base.dev, panthor_vm_unmap_range(vm, gpu_va, bo->base.base.size));
> +	panthor_vm_free_va(vm, bo->va_node);
> +	bo->va_node = NULL;
> +	drm_gem_object_put(&bo->base.base);
> +}
> +
> +/**
> + * panthor_gem_create_and_map() - Create and map a GEM object to a VM
> + * @ptdev: Device.
> + * @vm: VM to map the GEM to.
> + * @bo_flags: Combination of drm_panthor_bo_flags flags.
> + * @vm_map_flags: Combination of drm_panthor_vm_bind_op_flags (only those
> + * that are related to map operations).
> + * @gpu_va: Pointer holding the GPU address assigned when mapping to the VM.
> + * If *gpu_va == PANTHOR_GEM_ALLOC_VA, a virtual address range will be allocated
> + * and the allocated address returned, otherwise *gpu_va is used directly.
> + * @cpu_va: Pointer holding the kernel CPU mapping. If NULL, the GEM object
> + * is not CPU-mapped.
> + *
> + * Return: A valid pointer in case of success, an ERR_PTR() otherwise.
> + */
> +struct panthor_gem_object *
> +panthor_gem_create_and_map(struct panthor_device *ptdev, struct panthor_vm *vm,
> +			   size_t size, u32 bo_flags, u32 vm_map_flags,
> +			   u64 *gpu_va, void **cpu_va)
> +{
> +	struct drm_gem_shmem_object *obj;
> +	struct panthor_gem_object *bo;
> +	int ret;
> +
> +	obj = drm_gem_shmem_create(&ptdev->base, size);
> +	if (!obj)
> +		return ERR_PTR(-ENOMEM);
> +
> +	bo = to_panthor_bo(&obj->base);
> +	bo->flags = bo_flags;
> +	bo->exclusive_vm = panthor_vm_get(vm);
> +	bo->base.base.resv = panthor_vm_resv(vm);
> +
> +	if (*gpu_va == PANTHOR_GEM_ALLOC_VA) {
> +		bo->va_node = panthor_vm_alloc_va(vm, obj->base.size);
> +
> +		if (IS_ERR(bo->va_node)) {
> +			ret = PTR_ERR(bo->va_node);
> +			bo->va_node = NULL;
> +			goto err_put_obj;
> +		}
> +
> +		*gpu_va = bo->va_node->start;
> +	}
> +
> +	ret = panthor_vm_map_bo_range(vm, bo, 0, obj->base.size, *gpu_va, vm_map_flags);
> +	if (ret)
> +		goto err_put_obj;
> +
> +	if (cpu_va) {
> +		struct iosys_map map;
> +		int ret;
> +
> +		ret = drm_gem_vmap_unlocked(&obj->base, &map);
> +		if (ret)
> +			goto err_vm_unmap_range;
> +
> +		*cpu_va = map.vaddr;
> +	}
> +
> +	return bo;
> +
> +err_vm_unmap_range:
> +	panthor_vm_unmap_range(vm, *gpu_va, obj->base.size);
> +
> +err_put_obj:
> +	drm_gem_object_put(&obj->base);
> +	return ERR_PTR(ret);
> +}
> +
> +static int panthor_gem_mmap(struct drm_gem_object *obj, struct vm_area_struct *vma)
> +{
> +	struct panthor_gem_object *bo = to_panthor_bo(obj);
> +
> +	/* Don't allow mmap on objects that have the NO_MMAP flag set. */
> +	if (bo->flags & DRM_PANTHOR_BO_NO_MMAP)
> +		return -EINVAL;
> +
> +	return drm_gem_shmem_object_mmap(obj, vma);
> +}
> +
> +static struct dma_buf *
> +panthor_gem_prime_export(struct drm_gem_object *obj, int flags)
> +{
> +	/* We can't export GEMs that have an exclusive VM. */
> +	if (to_panthor_bo(obj)->exclusive_vm)
> +		return ERR_PTR(-EINVAL);
> +
> +	return drm_gem_prime_export(obj, flags);
> +}
> +
> +static const struct drm_gem_object_funcs panthor_gem_funcs = {
> +	.free = panthor_gem_free_object,
> +	.print_info = drm_gem_shmem_object_print_info,
> +	.pin = drm_gem_shmem_object_pin,
> +	.unpin = drm_gem_shmem_object_unpin,
> +	.get_sg_table = drm_gem_shmem_object_get_sg_table,
> +	.vmap = drm_gem_shmem_object_vmap,
> +	.vunmap = drm_gem_shmem_object_vunmap,
> +	.mmap = panthor_gem_mmap,
> +	.export = panthor_gem_prime_export,
> +	.vm_ops = &drm_gem_shmem_vm_ops,
> +};
> +
> +/**
> + * panthor_gem_create_object - Implementation of driver->gem_create_object.
> + * @dev: DRM device
> + * @size: Size in bytes of the memory the object will reference
> + *
> + * This lets the GEM helpers allocate object structs for us, and keep
> + * our BO stats correct.
> + */
> +struct drm_gem_object *panthor_gem_create_object(struct drm_device *ddev, size_t size)
> +{
> +	struct panthor_device *ptdev = container_of(ddev, struct panthor_device, base);
> +	struct panthor_gem_object *obj;
> +
> +	obj = kzalloc(sizeof(*obj), GFP_KERNEL);
> +	if (!obj)
> +		return ERR_PTR(-ENOMEM);
> +
> +	obj->base.base.funcs = &panthor_gem_funcs;
> +	obj->base.map_wc = !ptdev->coherent;
> +	mutex_init(&obj->gpuva_list_lock);
> +	drm_gem_gpuva_set_lock(&obj->base.base, &obj->gpuva_list_lock);
> +
> +	return &obj->base.base;
> +}
> +
> +/**
> + * panthor_gem_create_with_handle() - Create a GEM object and attach it to a handle.
> + * @file: DRM file.
> + * @ddev: DRM device.
> + * @exclusive_vm: Exclusive VM. Not NULL if the GEM object can't be shared.
> + * @size: Size of the GEM object to allocate.
> + * @flags: Combination of drm_panthor_bo_flags flags.
> + * @handle: Pointer holding the handle pointing to the new GEM object.
> + *
> + * Return: A valid pointer on success, an ERR_PTR() otherwise.
> + */
> +struct panthor_gem_object *
> +panthor_gem_create_with_handle(struct drm_file *file,
> +			       struct drm_device *ddev,
> +			       struct panthor_vm *exclusive_vm,
> +			       size_t size,
> +			       u32 flags, u32 *handle)
> +{
> +	int ret;
> +	struct drm_gem_shmem_object *shmem;
> +	struct panthor_gem_object *bo;
> +
> +	shmem = drm_gem_shmem_create(ddev, size);
> +	if (IS_ERR(shmem))
> +		return ERR_CAST(shmem);
> +
> +	bo = to_panthor_bo(&shmem->base);
> +	bo->flags = flags;
> +
> +	if (exclusive_vm) {
> +		bo->exclusive_vm = panthor_vm_get(exclusive_vm);
> +		bo->base.base.resv = panthor_vm_resv(exclusive_vm);
> +	}
> +
> +	/*
> +	 * Allocate an id of idr table where the obj is registered
> +	 * and handle has the id what user can see.
> +	 */
> +	ret = drm_gem_handle_create(file, &shmem->base, handle);
> +	/* drop reference from allocate - handle holds it now. */
> +	drm_gem_object_put(&shmem->base);
> +	if (ret)
> +		return ERR_PTR(ret);
> +
> +	return bo;
> +}

This function might be better just returning a simple int. The
"with_handle" approach means that doing anything much with the returned
object is dodgy (because another user space thread could have already
guessed the handle), and anyway the only caller
(panthor_ioctl_bo_create()) doesn't use the object and just extracts the
error code (if any).

Steve

> diff --git a/drivers/gpu/drm/panthor/panthor_gem.h b/drivers/gpu/drm/panthor/panthor_gem.h
> new file mode 100644
> index 000000000000..07babadc7623
> --- /dev/null
> +++ b/drivers/gpu/drm/panthor/panthor_gem.h
> @@ -0,0 +1,96 @@
> +/* SPDX-License-Identifier: GPL-2.0 or MIT */
> +/* Copyright 2019 Linaro, Ltd, Rob Herring <robh@kernel.org> */
> +/* Copyright 2023 Collabora ltd. */
> +
> +#ifndef __PANTHOR_GEM_H__
> +#define __PANTHOR_GEM_H__
> +
> +#include <drm/drm_gem_shmem_helper.h>
> +#include <drm/drm_mm.h>
> +
> +#include <linux/rwsem.h>
> +
> +struct panthor_vm;
> +
> +/**
> + * struct panthor_gem_object - Driver specific GEM object.
> + */
> +struct panthor_gem_object {
> +	/** @base: Inherit from drm_gem_shmem_object. */
> +	struct drm_gem_shmem_object base;
> +
> +	/**
> +	 * @va_node: VA space allocated to this GEM.
> +	 *
> +	 * Should be NULL for all GEM objects managed by userspace.
> +	 *
> +	 * Not NULL when %PANTHOR_GEM_ALLOC_VA is passed as an address, in
> +	 * which case the GEM logic will auto-allocate a VA range before mapping
> +	 * to the VM.
> +	 *
> +	 * @exclusive_vm must be != NULL.
> +	 */
> +	struct drm_mm_node *va_node;
> +
> +	/**
> +	 * @exclusive_vm: Exclusive VM this GEM object can be mapped to.
> +	 *
> +	 * If @exclusive_vm != NULL, any attempt to bind the GEM to a different
> +	 * VM will fail.
> +	 *
> +	 * All FW memory objects have this field set to the MCU VM.
> +	 */
> +	struct panthor_vm *exclusive_vm;
> +
> +	/**
> +	 * @gpuva_list_lock: Custom GPUVA lock.
> +	 *
> +	 * Used to protect insertion of drm_gpuva elements to the
> +	 * drm_gem_object.gpuva.list list.
> +	 *
> +	 * We can't use the GEM resv for that, because drm_gpuva_link() is
> +	 * called in a dma-signaling path, where we're not allowed to take
> +	 * resv locks.
> +	 */
> +	struct mutex gpuva_list_lock;
> +
> +	/** @flags: Combination of drm_panthor_bo_flags flags. */
> +	u32 flags;
> +};
> +
> +static inline
> +struct panthor_gem_object *to_panthor_bo(struct drm_gem_object *obj)
> +{
> +	return container_of(to_drm_gem_shmem_obj(obj), struct panthor_gem_object, base);
> +}
> +
> +struct drm_gem_object *panthor_gem_create_object(struct drm_device *ddev, size_t size);
> +
> +struct drm_gem_object *
> +panthor_gem_prime_import_sg_table(struct drm_device *ddev,
> +				  struct dma_buf_attachment *attach,
> +				  struct sg_table *sgt);
> +
> +struct panthor_gem_object *
> +panthor_gem_create_with_handle(struct drm_file *file,
> +			       struct drm_device *ddev,
> +			       struct panthor_vm *exclusive_vm,
> +			       size_t size,
> +			       u32 flags,
> +			       uint32_t *handle);
> +
> +void panthor_gem_unmap_and_put(struct panthor_vm *vm, struct panthor_gem_object *bo,
> +			       u64 gpu_va, void *cpu_va);
> +
> +/*
> + * PANTHOR_GEM_ALLOC_VA: Use this magic address when you want the GEM
> + * logic to auto-allocate the virtual address in the reserved kernel VA range.
> + */
> +#define PANTHOR_GEM_ALLOC_VA		~0ull
> +
> +struct panthor_gem_object *
> +panthor_gem_create_and_map(struct panthor_device *ptdev, struct panthor_vm *vm,
> +			   size_t size, u32 bo_flags, u32 vm_map_flags,
> +			   u64 *gpu_va, void **cpu_va);
> +
> +#endif /* __PANTHOR_GEM_H__ */