[PATCH 2/3] drm/xe/migrate: don't overflow max copy size

[Summers, Stuart]

On Wed, 2025-07-30 at 15:33 +0100, Matthew Auld wrote:
> With non-page aligned copy, we need to use byte aligned pitch,
> however
> the size itself might still be close to our maximum of ~8M, and so
> the
> dimensions of the copy can easily exceed the S16_MAX limit of the
> copy
> command leading to the following assert:
> 
> xe 0000:03:00.0: [drm] Assertion `size / pitch <= ((s16)(((u16)~0U)
> >> 1))` failed!
> platform: BATTLEMAGE subplatform: 1
> graphics: Xe2_HPG 20.01 step A0
> media: Xe2_HPM 13.01 step A1
> tile: 0 VRAM 10.0 GiB
> GT: 0 type 1
> 
> WARNING: CPU: 23 PID: 10605 at drivers/gpu/drm/xe/xe_migrate.c:673
> emit_copy+0x4b5/0x4e0 [xe]
> 
> To fix this account for the pitch when calculating the number of
> current
> bytes to copy.
> 
> Fixes: 270172f64b11 ("drm/xe: Update xe_ttm_access_memory to use GPU
> for non-visible access")
> Signed-off-by: Matthew Auld <matthew.auld at intel.com>
> Cc: Maciej Patelczyk <maciej.patelczyk at intel.com>
> Cc: Matthew Brost <matthew.brost at intel.com>
> ---
>  drivers/gpu/drm/xe/xe_migrate.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/gpu/drm/xe/xe_migrate.c
> b/drivers/gpu/drm/xe/xe_migrate.c
> index b6bdc9bd32b0..daca18b5b45f 100644
> --- a/drivers/gpu/drm/xe/xe_migrate.c
> +++ b/drivers/gpu/drm/xe/xe_migrate.c
> @@ -2056,6 +2056,12 @@ int xe_migrate_access_memory(struct xe_migrate
> *m, struct xe_bo *bo,
>                 else
>                         current_bytes = min_t(int, bytes_left,
> cursor.size);
>  
> +               if (current_bytes & ~PAGE_MASK) {
> +                       int pitch = 4;

This 4 is ndwords right? It would be nice to have a macro here instead
of just assuming that all over this file. But not a review blocker..

Reviewed-by: Stuart Summers <stuart.summers at intel.com>

> +
> +                       current_bytes = min_t(int, current_bytes,
> S16_MAX * pitch);
> +               }
> +
>                 if (fence)
>                         dma_fence_put(fence);
>