Re: [PATCH v8 4/6] drm/xe: apply debug page-size allocation policy to user BOs

["Ghimiray, Himal Prasad" <himal.prasad.ghimiray@intel.com>]

On 22-07-2026 20:07, Nareshkumar Gollakoti wrote:
> Apply the debug page-size allocation policy during user BO creation.
> 
> When page-size allocation control is enabled, override the user BO
> page-size selection flags based on the selected debug mode and round the
> requested size up to the corresponding granularity:
>    - 2M mode selects 2M handling
>    - 1G mode selects 1G handling
>    - mixed mode selects the page size from the current mixed-mode index
> 
> This is intended for internal debug and validation flows. When the
> control mode is left at the default setting, the normal user BO creation
> path is unchanged.
> 
> v2
> - ensure debug page-size allocation does not
>    affect the default path (sashiko)
> - rework synchronization for concurrent access (sashiko)
> - refactor commit message for readability
> 
> v3
> - update user BO size alignment based on debug policy mode
> - reword commit message
> - ensure normal user flow is unchanged when debug policy is disabled
> 
> v4(sashiko)
> - limit debug page-size policy application to VRAM BOs
> - do not override preexisting page-size requirement flags
> - advance mixed-mode index only after successful
>    BO create ioctl completion
> - add overflow checks before ALIGN() in debug page-size handling
> - ensure CONFIG_DRM_XE_DEBUG_PAGE_SIZE enabled and it is dgfx
> 
> v5(Himal)
> v5:
> - Guard debug page-size policy paths with CONFIG_DRM_XE_DEBUG_PAGE_SIZE
> - Leave the normal BO creation path unchanged
>    when no debug mode is selected
> 
> v8(Himal)
> - Avoid current index increment for system BO's
> - Simplify mixed mode align logic by changing array to struct array
> - Have a inline check if it is on debug mode or not
> - Avoid condition compiled debug in function code blocks
> 

Looks got to me.

Reviewed-by: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>

> Signed-off-by: Nareshkumar Gollakoti <naresh.kumar.g@intel.com>
> ---
>   drivers/gpu/drm/xe/xe_bo.c | 148 +++++++++++++++++++++++++++++++++++++
>   1 file changed, 148 insertions(+)
> 
> diff --git a/drivers/gpu/drm/xe/xe_bo.c b/drivers/gpu/drm/xe/xe_bo.c
> index cf0b7b35c331..929669f18788 100644
> --- a/drivers/gpu/drm/xe/xe_bo.c
> +++ b/drivers/gpu/drm/xe/xe_bo.c
> @@ -2640,6 +2640,145 @@ static struct xe_bo *xe_bo_create_novm(struct xe_device *xe, struct xe_tile *til
>   	return ret ? ERR_PTR(ret) : bo;
>   }
>   
> +#ifdef CONFIG_DRM_XE_DEBUG_PAGE_SIZE
> +static void xe_bo_debug_mixed_mode_cur_index_advance(struct xe_device *xe, struct xe_bo *bo)
> +{
> +	if (!xe_debug_page_size_mode_is_mixed(xe))
> +		return;
> +
> +	if (!(bo->flags & XE_BO_FLAG_VRAM_MASK) ||
> +	    !(bo->flags & XE_BO_FLAG_USER))
> +		return;
> +
> +	mutex_lock(&xe->page_size_alloc_ctrl.lock);
> +	if (xe->page_size_alloc_ctrl.mode == XE_PAGE_SIZE_ALLOC_CTRL_MODE_MIXED)
> +		xe->page_size_alloc_ctrl.cur_index++;
> +	mutex_unlock(&xe->page_size_alloc_ctrl.lock);
> +}
> +
> +static bool xe_size_align_overflows(size_t size, size_t align)
> +{
> +	return size > SIZE_MAX - (align - 1);
> +}
> +
> +static u32 get_flag_from_cur_index_in_mixed_mode(struct xe_device *xe, size_t *align_size,
> +						 int *err)
> +{
> +	static const struct {
> +		u32    flag;
> +		size_t align;
> +	} map[] = {
> +		{ 0,                     SZ_4K  }, /* default: 4K, no flag */
> +		{ XE_BO_FLAG_NEEDS_64K,  SZ_64K },
> +		{ XE_BO_FLAG_NEEDS_2M,   SZ_2M  },
> +		{ XE_BO_FLAG_NEEDS_1G,   SZ_1G  },
> +	};
> +	u32 idx;
> +	const typeof(*map) *entry;
> +
> +	lockdep_assert_held(&xe->page_size_alloc_ctrl.lock);
> +
> +	*err = 0;
> +	idx = xe->page_size_alloc_ctrl.cur_index % ARRAY_SIZE(map);
> +
> +	entry = &map[idx];
> +
> +	if (!entry->flag)
> +		return 0;
> +
> +	if (xe_size_align_overflows(*align_size, entry->align)) {
> +		*err = -EINVAL;
> +		return 0;
> +	}
> +	*align_size = ALIGN(*align_size, entry->align);
> +
> +	return entry->flag;
> +}
> +
> +static int xe_bo_apply_debug_page_size_policy(struct xe_device *xe,
> +					      u32 *bo_flags,
> +					      size_t *size)
> +{
> +	enum xe_page_size_alloc_ctrl_mode mode;
> +	u32 want = 0;
> +	size_t align_size = *size;
> +	int err = 0;
> +
> +	/*
> +	 * The debug page-size policy is only meaningful for BOs placed in
> +	 * VRAM, where the downstream BO init path can
> +	 * actually honor the corresponding minimum page-size requirement.
> +	 */
> +	if (!(*bo_flags & XE_BO_FLAG_VRAM_MASK))
> +		return 0;
> +
> +	/*
> +	 * Do not override existing page-size requirement flags, since they
> +	 * may reflect functional requirements for specific BO types.
> +	 */
> +	if (*bo_flags & (XE_BO_FLAG_NEEDS_64K |
> +			 XE_BO_FLAG_NEEDS_2M |
> +			 XE_BO_FLAG_NEEDS_1G))
> +		return 0;
> +
> +	if (!READ_ONCE(xe->page_size_alloc_ctrl.mode))
> +		return 0;
> +
> +	mutex_lock(&xe->page_size_alloc_ctrl.lock);
> +
> +	mode = xe->page_size_alloc_ctrl.mode;
> +	if (mode == XE_PAGE_SIZE_ALLOC_CTRL_MODE_NONE) {
> +		goto out_unlock;
> +	} else if (mode == XE_PAGE_SIZE_ALLOC_CTRL_MODE_ONLY_2M) {
> +		if (xe_size_align_overflows(align_size, SZ_2M)) {
> +			err = -EINVAL;
> +			goto out_unlock;
> +		}
> +		want = XE_BO_FLAG_NEEDS_2M;
> +		align_size = ALIGN(align_size, SZ_2M);
> +	} else if (mode == XE_PAGE_SIZE_ALLOC_CTRL_MODE_ONLY_1G) {
> +		if (xe_size_align_overflows(align_size, SZ_1G)) {
> +			err = -EINVAL;
> +			goto out_unlock;
> +		}
> +		want = XE_BO_FLAG_NEEDS_1G;
> +		align_size = ALIGN(align_size, SZ_1G);
> +	} else if (mode == XE_PAGE_SIZE_ALLOC_CTRL_MODE_MIXED) {
> +		want = get_flag_from_cur_index_in_mixed_mode(xe, &align_size, &err);
> +		if (err)
> +			goto out_unlock;
> +	} else {
> +		goto out_unlock;
> +	}
> +
> +	mutex_unlock(&xe->page_size_alloc_ctrl.lock);
> +
> +	*bo_flags |= want;
> +	/*
> +	 * Apply the debug page-size policy by rounding the user BO size up to
> +	 * the selected granularity.
> +	 */
> +	*size = align_size;
> +	return err;
> +
> +out_unlock:
> +	mutex_unlock(&xe->page_size_alloc_ctrl.lock);
> +	return err;
> +}
> +#else
> +static int xe_bo_apply_debug_page_size_policy(struct xe_device *xe,
> +					      u32 *bo_flags,
> +					      size_t *size)
> +{
> +	return 0;
> +}
> +
> +static void xe_bo_debug_mixed_mode_cur_index_advance(struct xe_device *xe,
> +						     struct xe_bo *bo)
> +{
> +}
> +#endif
> +
>   /**
>    * xe_bo_create_user() - Create a user BO
>    * @xe: The xe device.
> @@ -2660,9 +2799,16 @@ struct xe_bo *xe_bo_create_user(struct xe_device *xe,
>   				u32 flags, struct drm_exec *exec)
>   {
>   	struct xe_bo *bo;
> +	int err = 0;
>   
>   	flags |= XE_BO_FLAG_USER;
>   
> +	if (xe_debug_page_size_mode_not_none(xe)) {
> +		err = xe_bo_apply_debug_page_size_policy(xe, &flags, &size);
> +		if (err)
> +			return ERR_PTR(err);
> +	}
> +
>   	if (vm || exec) {
>   		xe_assert(xe, exec);
>   		bo = __xe_bo_create_locked(xe, NULL, vm, size, 0, ~0ULL,
> @@ -3477,6 +3623,8 @@ int xe_gem_create_ioctl(struct drm_device *dev, void *data,
>   	if (err)
>   		goto out_bulk;
>   
> +	xe_bo_debug_mixed_mode_cur_index_advance(xe, bo);
> +
>   	args->handle = handle;
>   	goto out_put;
>