Re: [PATCH] drm/panfrost: Don't try to map on error faults

From: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
To: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Cc: David Airlie <airlied@linux.ie>,
	linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
	Steven Price <steven.price@arm.com>
Subject: Re: [PATCH] drm/panfrost: Don't try to map on error faults
Date: Wed, 5 Feb 2020 07:24:23 -0500	[thread overview]
Message-ID: <20200205122423.GA2903@kevin> (raw)
In-Reply-To: <20200205100719.24999-1-tomeu.vizoso@collabora.com>

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Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com> 

Although it might be nice to

	#define TRANSLATION_FAULT_LEVEL1 0xC1
	...
	#define TRANSLATION_FAULT_LEVEL4 0xC4

and then use semantic names instead of magic values. Minimally maybe add
a comment explaining that.

On Wed, Feb 05, 2020 at 11:07:16AM +0100, Tomeu Vizoso wrote:
> If the exception type isn't one of the normal faults, don't try to map
> and instead go straight to a terminal fault.
> 
> Otherwise, we can get flooded by kernel warnings and further faults.
> 
> Signed-off-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
> ---
>  drivers/gpu/drm/panfrost/panfrost_mmu.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panfrost/panfrost_mmu.c b/drivers/gpu/drm/panfrost/panfrost_mmu.c
> index 763cfca886a7..80abddb4544c 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_mmu.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_mmu.c
> @@ -596,8 +596,9 @@ static irqreturn_t panfrost_mmu_irq_handler_thread(int irq, void *data)
>  		source_id = (fault_status >> 16);
>  
>  		/* Page fault only */
> -		if ((status & mask) == BIT(i)) {
> -			WARN_ON(exception_type < 0xC1 || exception_type > 0xC4);
> +		if ((status & mask) == BIT(i) &&
> +		     exception_type >= 0xC1 &&
> +		     exception_type <= 0xC4) {
>  
>  			ret = panfrost_mmu_map_fault_addr(pfdev, i, addr);
>  			if (!ret) {
> -- 
> 2.21.0
> 

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