[PATCH v5 08/23] drm/xe: Allow CPU address mirror VMA unbind with gpu bindings for madvise

[Matthew Brost]

On Tue, Jul 22, 2025 at 07:05:11PM +0530, Himal Prasad Ghimiray wrote:
> In the case of the MADVISE ioctl, if the start or end addresses fall
> within a VMA and existing SVM ranges are present, remove the existing
> SVM mappings. Then, continue with ops_parse to create new VMAs by REMAP
> unmapping of old one.
> 
> v2 (Matthew Brost)
> - Use vops flag to call unmapping of ranges in vm_bind_ioctl_ops_parse
> - Rename the function
> 
> v3
> - Fix doc
> 
> Signed-off-by: Himal Prasad Ghimiray <himal.prasad.ghimiray at intel.com>
> ---
>  drivers/gpu/drm/xe/xe_svm.c | 28 ++++++++++++++++++++++++++++
>  drivers/gpu/drm/xe/xe_svm.h |  7 +++++++
>  drivers/gpu/drm/xe/xe_vm.c  |  8 ++++++--
>  3 files changed, 41 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_svm.c b/drivers/gpu/drm/xe/xe_svm.c
> index a7ff5975873f..ce8a71b80811 100644
> --- a/drivers/gpu/drm/xe/xe_svm.c
> +++ b/drivers/gpu/drm/xe/xe_svm.c
> @@ -933,6 +933,34 @@ bool xe_svm_has_mapping(struct xe_vm *vm, u64 start, u64 end)
>  	return drm_gpusvm_has_mapping(&vm->svm.gpusvm, start, end);
>  }
>  
> +/**
> + * xe_svm_unmap_address_range - UNMAP SVM mappings and ranges
> + * @vm: The VM
> + * @start: start addr
> + * @end: end addr
> + *
> + * This function UNMAPS svm ranges if start or end address are inside them.
> + */
> +void xe_svm_unmap_address_range(struct xe_vm *vm, u64 start, u64 end)
> +{
> +	struct drm_gpusvm_notifier *notifier, *next;
> +
> +	lockdep_assert_held_write(&vm->lock);
> +
> +	drm_gpusvm_for_each_notifier_safe(notifier, next, &vm->svm.gpusvm, start, end) {
> +		struct drm_gpusvm_range *range, *__next;
> +
> +		drm_gpusvm_for_each_range_safe(range, __next, notifier, start, end) {
> +			if (start > drm_gpusvm_range_start(range) ||
> +			    end < drm_gpusvm_range_end(range)) {
> +				if (IS_DGFX(vm->xe) && xe_svm_range_in_vram(to_xe_range(range)))
> +					drm_gpusvm_range_evict(&vm->svm.gpusvm, range);
> +				__xe_svm_garbage_collector(vm, to_xe_range(range));

There is a corner here - the range could be in the garbage collector
list...

I think to fix you have to do this:

drm_gpusvm_range_get(range);
__xe_svm_garbage_collector(vm, to_xe_range(range));
if (!list_empty(&to_xe_range(range)->garbage_collector_link)) {
	spin_lock(&vm->svm.garbage_collector.list_lock);
	list_del(&to_xe_range(range)->garbage_collector_link);	
	spin_unlock(&vm->svm.garbage_collector.list_lock);
}
drm_gpusvm_range_put(range);

A little convoluted as it is only safe to check if the range is in the
garbage collector list after it has been removed from the notifier,
hence the need for extra ref counting here.

Also I believe this code path will need an IGT specifically to test this
code path.

Roughly...

buf = aligned_alloc(SZ_2M, SZ_2M);
fault_in_buf_on_gpu();
madvise(buf, SZ_1M, some attribute);
fault_in_buf_on_gpu();	/* Ideally showing different behavior between 2 chunks */
read_buf_back_via_cpu();

Matt

> +			}
> +		}
> +	}
> +}
> +
>  /**
>   * xe_svm_bo_evict() - SVM evict BO to system memory
>   * @bo: BO to evict
> diff --git a/drivers/gpu/drm/xe/xe_svm.h b/drivers/gpu/drm/xe/xe_svm.h
> index da9a69ea0bb1..754d56b4d255 100644
> --- a/drivers/gpu/drm/xe/xe_svm.h
> +++ b/drivers/gpu/drm/xe/xe_svm.h
> @@ -90,6 +90,8 @@ bool xe_svm_range_validate(struct xe_vm *vm,
>  
>  u64 xe_svm_find_vma_start(struct xe_vm *vm, u64 addr, u64 end,  struct xe_vma *vma);
>  
> +void xe_svm_unmap_address_range(struct xe_vm *vm, u64 start, u64 end);
> +
>  /**
>   * xe_svm_range_has_dma_mapping() - SVM range has DMA mapping
>   * @range: SVM range
> @@ -303,6 +305,11 @@ u64 xe_svm_find_vma_start(struct xe_vm *vm, u64 addr, u64 end, struct xe_vma *vm
>  	return ULONG_MAX;
>  }
>  
> +static inline
> +void xe_svm_unmap_address_range(struct xe_vm *vm, u64 start, u64 end)
> +{
> +}
> +
>  #define xe_svm_assert_in_notifier(...) do {} while (0)
>  #define xe_svm_range_has_dma_mapping(...) false
>  
> diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c
> index a56384325f4d..7f3d0ad04b3f 100644
> --- a/drivers/gpu/drm/xe/xe_vm.c
> +++ b/drivers/gpu/drm/xe/xe_vm.c
> @@ -2663,8 +2663,12 @@ static int vm_bind_ioctl_ops_parse(struct xe_vm *vm, struct drm_gpuva_ops *ops,
>  				end = op->base.remap.next->va.addr;
>  
>  			if (xe_vma_is_cpu_addr_mirror(old) &&
> -			    xe_svm_has_mapping(vm, start, end))
> -				return -EBUSY;
> +			    xe_svm_has_mapping(vm, start, end)) {
> +				if (vops->flags & XE_VMA_OPS_FLAG_MADVISE)
> +					xe_svm_unmap_address_range(vm, start, end);
> +				else
> +					return -EBUSY;
> +			}
>  
>  			op->remap.start = xe_vma_start(old);
>  			op->remap.range = xe_vma_size(old);
> -- 
> 2.34.1
>