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Message-ID: <7951dc11-6047-6beb-8ef8-98c862e26ec3@amd.com>
Date: Thu, 21 Sep 2023 09:39:08 +0200
From: Christian König <christian.koenig@....com>
To: Danilo Krummrich <dakr@...hat.com>, airlied@...il.com,
daniel@...ll.ch, matthew.brost@...el.com,
thomas.hellstrom@...ux.intel.com, sarah.walker@...tec.com,
donald.robson@...tec.com, boris.brezillon@...labora.com,
faith.ekstrand@...labora.com
Cc: dri-devel@...ts.freedesktop.org, nouveau@...ts.freedesktop.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH drm-misc-next v4 4/8] drm/gpuvm: add common dma-resv per
struct drm_gpuvm
Am 20.09.23 um 16:42 schrieb Danilo Krummrich:
> Provide a common dma-resv for GEM objects not being used outside of this
> GPU-VM. This is used in a subsequent patch to generalize dma-resv,
> external and evicted object handling and GEM validation.
>
> Signed-off-by: Danilo Krummrich <dakr@...hat.com>
> ---
> drivers/gpu/drm/drm_gpuvm.c | 9 +++++++--
> drivers/gpu/drm/nouveau/nouveau_uvmm.c | 2 +-
> include/drm/drm_gpuvm.h | 17 ++++++++++++++++-
> 3 files changed, 24 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_gpuvm.c b/drivers/gpu/drm/drm_gpuvm.c
> index bfea4a8a19ec..cbf4b738a16c 100644
> --- a/drivers/gpu/drm/drm_gpuvm.c
> +++ b/drivers/gpu/drm/drm_gpuvm.c
> @@ -655,6 +655,7 @@ drm_gpuva_range_valid(struct drm_gpuvm *gpuvm,
> /**
> * drm_gpuvm_init() - initialize a &drm_gpuvm
> * @gpuvm: pointer to the &drm_gpuvm to initialize
> + * @drm: the drivers &drm_device
> * @name: the name of the GPU VA space
> * @start_offset: the start offset of the GPU VA space
> * @range: the size of the GPU VA space
> @@ -668,7 +669,7 @@ drm_gpuva_range_valid(struct drm_gpuvm *gpuvm,
> * &name is expected to be managed by the surrounding driver structures.
> */
> void
> -drm_gpuvm_init(struct drm_gpuvm *gpuvm,
> +drm_gpuvm_init(struct drm_gpuvm *gpuvm, struct drm_device *drm,
> const char *name,
> u64 start_offset, u64 range,
> u64 reserve_offset, u64 reserve_range,
> @@ -694,6 +695,8 @@ drm_gpuvm_init(struct drm_gpuvm *gpuvm,
> reserve_range)))
> __drm_gpuva_insert(gpuvm, &gpuvm->kernel_alloc_node);
> }
> +
> + drm_gem_private_object_init(drm, &gpuvm->d_obj, 0);
> }
> EXPORT_SYMBOL_GPL(drm_gpuvm_init);
>
> @@ -713,7 +716,9 @@ drm_gpuvm_destroy(struct drm_gpuvm *gpuvm)
> __drm_gpuva_remove(&gpuvm->kernel_alloc_node);
>
> WARN(!RB_EMPTY_ROOT(&gpuvm->rb.tree.rb_root),
> - "GPUVA tree is not empty, potentially leaking memory.");
> + "GPUVA tree is not empty, potentially leaking memory.\n");
> +
> + drm_gem_private_object_fini(&gpuvm->d_obj);
> }
> EXPORT_SYMBOL_GPL(drm_gpuvm_destroy);
>
> diff --git a/drivers/gpu/drm/nouveau/nouveau_uvmm.c b/drivers/gpu/drm/nouveau/nouveau_uvmm.c
> index 6c86b64273c3..a80ac8767843 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_uvmm.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_uvmm.c
> @@ -1836,7 +1836,7 @@ nouveau_uvmm_init(struct nouveau_uvmm *uvmm, struct nouveau_cli *cli,
> uvmm->kernel_managed_addr = kernel_managed_addr;
> uvmm->kernel_managed_size = kernel_managed_size;
>
> - drm_gpuvm_init(&uvmm->base, cli->name,
> + drm_gpuvm_init(&uvmm->base, cli->drm->dev, cli->name,
> NOUVEAU_VA_SPACE_START,
> NOUVEAU_VA_SPACE_END,
> kernel_managed_addr, kernel_managed_size,
> diff --git a/include/drm/drm_gpuvm.h b/include/drm/drm_gpuvm.h
> index 0e802676e0a9..6666c07d7c3e 100644
> --- a/include/drm/drm_gpuvm.h
> +++ b/include/drm/drm_gpuvm.h
> @@ -240,14 +240,29 @@ struct drm_gpuvm {
> * @ops: &drm_gpuvm_ops providing the split/merge steps to drivers
> */
> const struct drm_gpuvm_ops *ops;
> +
> + /**
> + * @d_obj: Dummy GEM object; used internally to pass the GPU VMs
> + * dma-resv to &drm_exec. Provides the GPUVM's &dma-resv.
> + */
> + struct drm_gem_object d_obj;
Yeah, as pointed out in the other mail that won't work like this.
The GPUVM contains GEM objects and therefore should probably have a
reference to those objects.
When those GEM objects now use the dma-resv object embedded inside the
GPUVM then they also need a reference to the GPUVM to make sure the
dma-resv object won't be freed before they are freed.
This is a circle reference dependency.
The simplest solution I can see is to let the driver provide the GEM
object to use. Amdgpu uses the root page directory object for this.
Apart from that I strongly think that we shouldn't let the GPUVM code
create a driver GEM object. We did that in TTM for the ghost objects and
it turned out to be a bad idea.
Regards,
Christian.
> };
>
> -void drm_gpuvm_init(struct drm_gpuvm *gpuvm, const char *name,
> +void drm_gpuvm_init(struct drm_gpuvm *gpuvm, struct drm_device *drm,
> + const char *name,
> u64 start_offset, u64 range,
> u64 reserve_offset, u64 reserve_range,
> const struct drm_gpuvm_ops *ops);
> void drm_gpuvm_destroy(struct drm_gpuvm *gpuvm);
>
> +/**
> + * drm_gpuvm_resv() - returns the &drm_gpuvm's &dma_resv
> + * @gpuvm__: the &drm_gpuvm
> + *
> + * Returns: a pointer to the &drm_gpuvm's &dma_resv
> + */
> +#define drm_gpuvm_resv(gpuvm__) (&(gpuvm__)->d_obj._resv)
> +
> static inline struct drm_gpuva *
> __drm_gpuva_next(struct drm_gpuva *va)
> {
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