Re: [PATCH v2 8/9] drm/xe/migrate: Introduce xe_migrate_reinit()

[Matthew Brost <matthew.brost@intel.com>]

On Fri, Feb 27, 2026 at 10:30:48PM +0530, Raag Jadav wrote:
> In preparation of usecases which require re-initializing migrate context
> after PCIe FLR, introduce xe_migrate_reinit() helper. Migrate exec queue
> and pt_bo already exist in migrate structure but since their contents live
> on VRAM, they are lost on PCIe FLR and need re-initialization.
> 
> Signed-off-by: Raag Jadav <raag.jadav@intel.com>
> ---
> v2: Re-initialize migrate context (Matthew Brost)
> ---
>  drivers/gpu/drm/xe/xe_gt.c      | 10 +++++
>  drivers/gpu/drm/xe/xe_migrate.c | 65 +++++++++++++++++++++++++--------
>  drivers/gpu/drm/xe/xe_migrate.h |  1 +
>  3 files changed, 61 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_gt.c b/drivers/gpu/drm/xe/xe_gt.c
> index ff4a4e769fb1..ab34312830e3 100644
> --- a/drivers/gpu/drm/xe/xe_gt.c
> +++ b/drivers/gpu/drm/xe/xe_gt.c
> @@ -966,6 +966,16 @@ void xe_gt_flr_prepare(struct xe_gt *gt)
>   */
>  int xe_gt_flr_done(struct xe_gt *gt)
>  {
> +	int err;
> +
> +	if (xe_gt_is_main_type(gt)) {
> +		struct xe_tile *tile = gt_to_tile(gt);
> +
> +		err = xe_migrate_reinit(tile->migrate);

I think there is work ahead for future platforms where multiple tiles
point to the same migrate object, so we’ll need to keep an eye on that.
Perhaps calling xe_migrate_reinit twice is harmless too.

Anyways the patch looks correct.

Reviewed-by: Matthew Brost <matthew.brost@intel.com>

> +		if (err)
> +			return err;
> +	}
> +
>  	return xe_uc_flr_done(&gt->uc);
>  }
>  
> diff --git a/drivers/gpu/drm/xe/xe_migrate.c b/drivers/gpu/drm/xe/xe_migrate.c
> index 333af7b57ae9..f4a2ad3ce601 100644
> --- a/drivers/gpu/drm/xe/xe_migrate.c
> +++ b/drivers/gpu/drm/xe/xe_migrate.c
> @@ -184,19 +184,11 @@ static void xe_migrate_program_identity(struct xe_device *xe, struct xe_vm *vm,
>  	xe_assert(xe, pos == vram_limit);
>  }
>  
> -static int xe_migrate_prepare_vm(struct xe_tile *tile, struct xe_migrate *m,
> -				 struct xe_vm *vm, struct drm_exec *exec)
> +static int xe_migrate_pt_bo_alloc(struct xe_tile *tile, struct xe_migrate *m,
> +				  struct xe_vm *vm, struct drm_exec *exec)
>  {
> -	struct xe_device *xe = tile_to_xe(tile);
> -	u16 pat_index = xe->pat.idx[XE_CACHE_WB];
> -	u8 id = tile->id;
> -	u32 num_entries = NUM_PT_SLOTS, num_level = vm->pt_root[id]->level;
> -#define VRAM_IDENTITY_MAP_COUNT	2
> -	u32 num_setup = num_level + VRAM_IDENTITY_MAP_COUNT;
> -#undef VRAM_IDENTITY_MAP_COUNT
> -	u32 map_ofs, level, i;
>  	struct xe_bo *bo, *batch = tile->mem.kernel_bb_pool->bo;
> -	u64 entry, pt29_ofs;
> +	u32 num_entries = NUM_PT_SLOTS;
>  
>  	/* Can't bump NUM_PT_SLOTS too high */
>  	BUILD_BUG_ON(NUM_PT_SLOTS > SZ_2M/XE_PAGE_SIZE);
> @@ -216,6 +208,24 @@ static int xe_migrate_prepare_vm(struct xe_tile *tile, struct xe_migrate *m,
>  	if (IS_ERR(bo))
>  		return PTR_ERR(bo);
>  
> +	m->pt_bo = bo;
> +	return 0;
> +}
> +
> +static void xe_migrate_prepare_vm(struct xe_tile *tile, struct xe_migrate *m,
> +				  struct xe_vm *vm, u32 *ofs)
> +{
> +	struct xe_device *xe = tile_to_xe(tile);
> +	u16 pat_index = xe->pat.idx[XE_CACHE_WB];
> +	u8 id = tile->id;
> +	u32 num_entries = NUM_PT_SLOTS, num_level = vm->pt_root[id]->level;
> +#define VRAM_IDENTITY_MAP_COUNT	2
> +	u32 num_setup = num_level + VRAM_IDENTITY_MAP_COUNT;
> +#undef VRAM_IDENTITY_MAP_COUNT
> +	u32 map_ofs, level, i;
> +	struct xe_bo *bo = m->pt_bo, *batch = tile->mem.kernel_bb_pool->bo;
> +	u64 entry, pt29_ofs;
> +
>  	/* PT30 & PT31 reserved for 2M identity map */
>  	pt29_ofs = xe_bo_size(bo) - 3 * XE_PAGE_SIZE;
>  	entry = vm->pt_ops->pde_encode_bo(bo, pt29_ofs);
> @@ -338,6 +348,12 @@ static int xe_migrate_prepare_vm(struct xe_tile *tile, struct xe_migrate *m,
>  		}
>  	}
>  
> +	if (ofs)
> +		*ofs = map_ofs;
> +}
> +
> +static void xe_migrate_suballoc_manager_init(struct xe_migrate *m, u32 map_ofs)
> +{
>  	/*
>  	 * Example layout created above, with root level = 3:
>  	 * [PT0...PT7]: kernel PT's for copy/clear; 64 or 4KiB PTE's
> @@ -363,9 +379,6 @@ static int xe_migrate_prepare_vm(struct xe_tile *tile, struct xe_migrate *m,
>  	drm_suballoc_manager_init(&m->vm_update_sa,
>  				  (size_t)(map_ofs / XE_PAGE_SIZE - NUM_KERNEL_PDE) *
>  				  NUM_VMUSA_UNIT_PER_PAGE, 0);
> -
> -	m->pt_bo = bo;
> -	return 0;
>  }
>  
>  /*
> @@ -416,12 +429,22 @@ static int xe_migrate_lock_prepare_vm(struct xe_tile *tile, struct xe_migrate *m
>  	struct xe_device *xe = tile_to_xe(tile);
>  	struct xe_validation_ctx ctx;
>  	struct drm_exec exec;
> +	u32 map_ofs;
>  	int err = 0;
>  
>  	xe_validation_guard(&ctx, &xe->val, &exec, (struct xe_val_flags) {}, err) {
>  		err = xe_vm_drm_exec_lock(vm, &exec);
> +		if (err)
> +			return err;
> +
>  		drm_exec_retry_on_contention(&exec);
> -		err = xe_migrate_prepare_vm(tile, m, vm, &exec);
> +
> +		err = xe_migrate_pt_bo_alloc(tile, m, vm, &exec);
> +		if (err)
> +			return err;
> +
> +		xe_migrate_prepare_vm(tile, m, vm, &map_ofs);
> +		xe_migrate_suballoc_manager_init(m, map_ofs);
>  		drm_exec_retry_on_contention(&exec);
>  		xe_validation_retry_on_oom(&ctx, &err);
>  	}
> @@ -429,6 +452,18 @@ static int xe_migrate_lock_prepare_vm(struct xe_tile *tile, struct xe_migrate *m
>  	return err;
>  }
>  
> +/**
> + * xe_migrate_reinit() - Re-initialize a migrate context
> + * @m: The migration context
> + *
> + * Returns: 0 on success, negative error code otherwise.
> + */
> +int xe_migrate_reinit(struct xe_migrate *m)
> +{
> +	xe_migrate_prepare_vm(m->tile, m, m->q->vm, NULL);
> +	return xe_exec_queue_reinit(m->q);
> +}
> +
>  /**
>   * xe_migrate_init() - Initialize a migrate context
>   * @m: The migration context
> diff --git a/drivers/gpu/drm/xe/xe_migrate.h b/drivers/gpu/drm/xe/xe_migrate.h
> index 1522afb37dcf..fffbcab8b2e3 100644
> --- a/drivers/gpu/drm/xe/xe_migrate.h
> +++ b/drivers/gpu/drm/xe/xe_migrate.h
> @@ -112,6 +112,7 @@ struct xe_migrate_pt_update {
>  
>  struct xe_migrate *xe_migrate_alloc(struct xe_tile *tile);
>  int xe_migrate_init(struct xe_migrate *m);
> +int xe_migrate_reinit(struct xe_migrate *m);
>  
>  struct dma_fence *xe_migrate_to_vram(struct xe_migrate *m,
>  				     unsigned long npages,
> -- 
> 2.43.0
>