[PATCH] drm/xe: Do not allow scratch page on long running jobs

[Matthew Brost]

On Thu, Sep 19, 2024 at 12:47:04PM +0200, Nirmoy Das wrote:
> This was agreed upon but not enforced, so enforce the limitation
> of not allowing scratch pages on long-running jobs unless absolutely
> required, which is currently the case for a DG2 SKU.
> 
> Cc: Gwan-gyeong Mun <gwan-gyeong.mun at intel.com>
> Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
> Cc: Matthew Brost <matthew.brost at intel.com>

I think this type of change we will need a maintainer to bless and
likely someone from the compute UMD.

It does LGTM, with that:
Acked-by: Matthew Brost <matthew.brost at intel.com>

> Cc: Stuart Summers <stuart.summers at intel.com>
> Cc: "Thomas Hellström" <thomas.hellstrom at linux.intel.com>
> Suggested-by: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> Signed-off-by: Nirmoy Das <nirmoy.das at intel.com>
> ---
>  drivers/gpu/drm/xe/xe_vm.c | 16 +++++++++++++++-
>  1 file changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c
> index a3d7cb7cfd22..92dc55f3479b 100644
> --- a/drivers/gpu/drm/xe/xe_vm.c
> +++ b/drivers/gpu/drm/xe/xe_vm.c
> @@ -1711,6 +1711,11 @@ find_ufence_get(struct xe_sync_entry *syncs, u32 num_syncs)
>  	return NULL;
>  }
>  
> +static bool xe_vm_device_requires_scratch_page(struct xe_device *xe)
> +{
> +	return XE_WA(xe_root_mmio_gt(xe), 14016763929);
> +}
> +
>  #define ALL_DRM_XE_VM_CREATE_FLAGS (DRM_XE_VM_CREATE_FLAG_SCRATCH_PAGE | \
>  				    DRM_XE_VM_CREATE_FLAG_LR_MODE | \
>  				    DRM_XE_VM_CREATE_FLAG_FAULT_MODE)
> @@ -1730,7 +1735,7 @@ int xe_vm_create_ioctl(struct drm_device *dev, void *data,
>  	if (XE_IOCTL_DBG(xe, args->extensions))
>  		return -EINVAL;
>  
> -	if (XE_WA(xe_root_mmio_gt(xe), 14016763929))
> +	if (xe_vm_device_requires_scratch_page(xe))
>  		args->flags |= DRM_XE_VM_CREATE_FLAG_SCRATCH_PAGE;
>  
>  	if (XE_IOCTL_DBG(xe, args->flags & DRM_XE_VM_CREATE_FLAG_FAULT_MODE &&
> @@ -1747,6 +1752,15 @@ int xe_vm_create_ioctl(struct drm_device *dev, void *data,
>  			 args->flags & DRM_XE_VM_CREATE_FLAG_FAULT_MODE))
>  		return -EINVAL;
>  
> +	/*
> +	 * Scratch page is disabled for long running job unless absolutely
> +	 * required as this can introduce hidden bugs.
> +	 */
> +	if (!xe_vm_device_requires_scratch_page(xe) &&
> +	    XE_IOCTL_DBG(xe, args->flags & DRM_XE_VM_CREATE_FLAG_SCRATCH_PAGE &&
> +			 (args->flags & DRM_XE_VM_CREATE_FLAG_LR_MODE)))
> +		return -EINVAL;
> +
>  	if (XE_IOCTL_DBG(xe, !(args->flags & DRM_XE_VM_CREATE_FLAG_LR_MODE) &&
>  			 args->flags & DRM_XE_VM_CREATE_FLAG_FAULT_MODE))
>  		return -EINVAL;
> -- 
> 2.46.0
>