Re: [PATCH 1/6] drm/xe/migrate: rework size restrictions for sram pte emit

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

On Wed, Oct 15, 2025 at 03:19:31PM +0100, Matthew Auld wrote:
> We allow the input size to not be aligned to PAGE_SIZE, which leads to
> various bugs in build_pt_update_batch_sram() for PAGE_SIZE > 4K systems.
> For example if ptes is exactly one gpu_page_size then the chunk size is
> rounded down to zero.  The simplest fix looks to be forcing PAGE_SIZE
> aligned inputs.
> 
> Signed-off-by: Matthew Auld <matthew.auld@intel.com>
> Cc: Matthew Brost <matthew.brost@intel.com>

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

> ---
>  drivers/gpu/drm/xe/xe_migrate.c | 13 ++++++++-----
>  1 file changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_migrate.c b/drivers/gpu/drm/xe/xe_migrate.c
> index 4ca48dd1cfd8..ff8e442bf519 100644
> --- a/drivers/gpu/drm/xe/xe_migrate.c
> +++ b/drivers/gpu/drm/xe/xe_migrate.c
> @@ -1798,6 +1798,8 @@ static void build_pt_update_batch_sram(struct xe_migrate *m,
>  	u32 ptes;
>  	int i = 0;
>  
> +	xe_tile_assert(m->tile, PAGE_ALIGNED(size));
> +
>  	ptes = DIV_ROUND_UP(size, gpu_page_size);
>  	while (ptes) {
>  		u32 chunk = min(MAX_PTE_PER_SDI, ptes);
> @@ -1811,12 +1813,13 @@ static void build_pt_update_batch_sram(struct xe_migrate *m,
>  		ptes -= chunk;
>  
>  		while (chunk--) {
> -			u64 addr = sram_addr[i].addr & ~(gpu_page_size - 1);
> -			u64 pte, orig_addr = addr;
> +			u64 addr = sram_addr[i].addr;
> +			u64 pte;
>  
>  			xe_tile_assert(m->tile, sram_addr[i].proto ==
>  				       DRM_INTERCONNECT_SYSTEM);
>  			xe_tile_assert(m->tile, addr);
> +			xe_tile_assert(m->tile, PAGE_ALIGNED(addr));
>  
>  again:
>  			pte = m->q->vm->pt_ops->pte_encode_addr(m->tile->xe,
> @@ -1827,7 +1830,7 @@ static void build_pt_update_batch_sram(struct xe_migrate *m,
>  
>  			if (gpu_page_size < PAGE_SIZE) {
>  				addr += XE_PAGE_SIZE;
> -				if (orig_addr + PAGE_SIZE != addr) {
> +				if (!PAGE_ALIGNED(addr)) {
>  					chunk--;
>  					goto again;
>  				}
> @@ -1918,10 +1921,10 @@ static struct dma_fence *xe_migrate_vram(struct xe_migrate *m,
>  
>  	if (use_pde)
>  		build_pt_update_batch_sram(m, bb, m->large_page_copy_pdes,
> -					   sram_addr, len + sram_offset, 1);
> +					   sram_addr, npages << PAGE_SHIFT, 1);
>  	else
>  		build_pt_update_batch_sram(m, bb, pt_slot * XE_PAGE_SIZE,
> -					   sram_addr, len + sram_offset, 0);
> +					   sram_addr, npages << PAGE_SHIFT, 0);
>  
>  	if (dir == XE_MIGRATE_COPY_TO_VRAM) {
>  		if (use_pde)
> -- 
> 2.51.0
>