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Date: Fri, 3 Feb 2023 12:12:19 +0100
From: Joerg Roedel <joro@8bytes.org>
To: Vasant Hegde <vasant.hegde@amd.com>
Cc: iommu@lists.linux.dev, robin.murphy@arm.com, will@kernel.org,
	suravee.suthikulpanit@amd.com, Matt Fagnani <matt.fagnani@bell.net>
Subject: Re: [PATCH 3/3] iommu/amd: Call BUG_ON in page fault hanlder path if
 domain is NULL
Message-ID: <Y9zsE800/NhF8unH@8bytes.org>
References: <20230113135956.5788-1-vasant.hegde@amd.com>
 <20230113135956.5788-3-vasant.hegde@amd.com>
 <Y9zVnkfEp3bC+UfL@8bytes.org>
 <8f161d2b-2c00-5a91-5799-36746af5b32c@amd.com>
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In-Reply-To: <8f161d2b-2c00-5a91-5799-36746af5b32c@amd.com>

Hi Vasant

On Fri, Feb 03, 2023 at 04:10:33PM +0530, Vasant Hegde wrote:
> Initially I was thinking of logging error message and return. But it will hit
> device faults continuously.  Also we don't have nice way to recover from this
> condition.
> 
> So I thought crashing here with explicit BUG_ON is better. But I agree with
> Robin's comment. We don't really get anything extra with BUG_ON. We should be
> able to figureout crash reason based on NULL pointer dereference easily.
> 
> Do you want me to just add explicit log here? Otherwise I am fine dropping this
> patch (3/3). I think we still need first two patches from this series.

The best for now is to print a ratelimited error message and just return
from the handler. The ratelimit ensures that no misbehaving device can
flood the kernel log.

Regards,

	Joerg