Re: [PATCH] Revert "drm/pagemap: Disable device-to-device migration"

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

On Wed, Feb 11, 2026 at 11:41:59AM +0100, Thomas Hellström wrote:
> With commit
> a69d1ab971a6 ("mm: Fix a hmm_range_fault() livelock / starvation problem")
> device-to-device migration is not functional again and the
> disabling can be reverted.
> 
> Add the above commit as a Fixes: tag in order for the revert to not
> take place unless that commit is present.
> 
> This reverts commit 10dd1eaa80a56d3cf6d7c36b5269c8fed617f001.
> 
> Cc: Matthew Brost <matthew.brost@intel.com>

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

> Fixes: a69d1ab971a6 ("mm: Fix a hmm_range_fault() livelock / starvation problem")
> Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> ---
>  drivers/gpu/drm/drm_pagemap.c | 14 ++------------
>  1 file changed, 2 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_pagemap.c b/drivers/gpu/drm/drm_pagemap.c
> index 38eca94f01a1..73438ba275bc 100644
> --- a/drivers/gpu/drm/drm_pagemap.c
> +++ b/drivers/gpu/drm/drm_pagemap.c
> @@ -480,18 +480,8 @@ int drm_pagemap_migrate_to_devmem(struct drm_pagemap_devmem *devmem_allocation,
>  		.start		= start,
>  		.end		= end,
>  		.pgmap_owner	= pagemap->owner,
> -		/*
> -		 * FIXME: MIGRATE_VMA_SELECT_DEVICE_PRIVATE intermittently
> -		 * causes 'xe_exec_system_allocator --r *race*no*' to trigger aa
> -		 * engine reset and a hard hang due to getting stuck on a folio
> -		 * lock. This should work and needs to be root-caused. The only
> -		 * downside of not selecting MIGRATE_VMA_SELECT_DEVICE_PRIVATE
> -		 * is that device-to-device migrations won’t work; instead,
> -		 * memory will bounce through system memory. This path should be
> -		 * rare and only occur when the madvise attributes of memory are
> -		 * changed or atomics are being used.
> -		 */
> -		.flags		= MIGRATE_VMA_SELECT_SYSTEM | MIGRATE_VMA_SELECT_DEVICE_COHERENT,
> +		.flags		= MIGRATE_VMA_SELECT_SYSTEM | MIGRATE_VMA_SELECT_DEVICE_COHERENT |
> +		MIGRATE_VMA_SELECT_DEVICE_PRIVATE,
>  	};
>  	unsigned long i, npages = npages_in_range(start, end);
>  	unsigned long own_pages = 0, migrated_pages = 0;
> -- 
> 2.52.0
>