Re: [PATCH] drm/i915: Disable read only ppgtt support for gen11

[Rodrigo Vivi <rodrigo.vivi@intel.com>]

On Thu, Apr 11, 2019 at 11:30:34AM +0300, Mika Kuoppala wrote:
> On gen11 writing to read only ppgtt page causes a gpu hang.
> This behaviour is different than with previous gen where
> read only ppgtt access is supported. On those, the write
> is just dropped without visible side effects.
> 
> Disable ro ppgtt support on gen11 until a solution can
> be found to bring it into line with its predecessors.
> 
> References: HSDES#1807136187
> References: https://bugzilla.freedesktop.org/show_bug.cgi?id=108569
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Signed-off-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/i915_gem_gtt.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
> index 736c845eb77f..caae8cdafc1a 100644
> --- a/drivers/gpu/drm/i915/i915_gem_gtt.c
> +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
> @@ -1548,8 +1548,13 @@ static struct i915_hw_ppgtt *gen8_ppgtt_create(struct drm_i915_private *i915)
>  
>  	ppgtt_init(i915, ppgtt);
>  
> -	/* From bdw, there is support for read-only pages in the PPGTT. */
> -	ppgtt->vm.has_read_only = true;
> +	/*
> +	 * From bdw, there is hw support for read-only pages in the PPGTT.
> +	 *
> +	 * Gen11 has HSDES#:1807136187 unresolved. Disable ro support
> +	 * for now.
> +	 */
> +	ppgtt->vm.has_read_only = INTEL_GEN(i915) != 11;

I believe it is safest to use < 11, no?!

>  
>  	/* There are only few exceptions for gen >=6. chv and bxt.
>  	 * And we are not sure about the latter so play safe for now.
> -- 
> 2.17.1
> 
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