Re: [PATCH] drm/xe: Add warn when level can not be zero.

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

On Tue, May 21, 2024 at 12:36:23PM +0200, Nirmoy Das wrote:
> At xe_pt_zap_ptes_entry() and xe_pt_stage_unbind_entry, the level cannot
> be 0. Therefore, add an independent check for the level. Since the level
> cannot be zero at this point, there is no need to check for `is_compact`,
> so remove that instead.
> 

This doesn't look right. Both xe_pt_zap_ptes_entry &
xe_pt_stage_unbind_entry can be at level 0 is 4K page entries are used,
right? CI looks good though so confused by that. I think maybe 2
independent VMAs would have to mapped within a 2M range for these paths
to decend to level 0. Maybe we don't have tests in place that do this.

Regardless please don't merge this until my concerns are addresesed.

Matt

> Cc: Matthew Auld <matthew.auld@intel.com>
> Signed-off-by: Nirmoy Das <nirmoy.das@intel.com>
> ---
>  drivers/gpu/drm/xe/xe_pt.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_pt.c b/drivers/gpu/drm/xe/xe_pt.c
> index 11dd0988ffda..cd60c009b679 100644
> --- a/drivers/gpu/drm/xe/xe_pt.c
> +++ b/drivers/gpu/drm/xe/xe_pt.c
> @@ -763,7 +763,7 @@ static int xe_pt_zap_ptes_entry(struct xe_ptw *parent, pgoff_t offset,
>  	pgoff_t end_offset;
>  
>  	XE_WARN_ON(!*child);
> -	XE_WARN_ON(!level && xe_child->is_compact);
> +	XE_WARN_ON(!level);
>  
>  	/*
>  	 * Note that we're called from an entry callback, and we're dealing
> @@ -1445,7 +1445,7 @@ static int xe_pt_stage_unbind_entry(struct xe_ptw *parent, pgoff_t offset,
>  	struct xe_pt *xe_child = container_of(*child, typeof(*xe_child), base);
>  
>  	XE_WARN_ON(!*child);
> -	XE_WARN_ON(!level && xe_child->is_compact);
> +	XE_WARN_ON(!level);
>  
>  	xe_pt_check_kill(addr, next, level - 1, xe_child, action, walk);
>  
> -- 
> 2.42.0
>