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From:   Christoph Hellwig <hch@lst.de>
To:     Qian Cai <quic_qiancai@quicinc.com>
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Subject: Re: [PATCH v14 06/12] swiotlb: Use is_swiotlb_force_bounce for
 swiotlb data bouncing
Message-ID: <20210624054315.GA25381@lst.de>
References: <20210619034043.199220-1-tientzu@chromium.org> <20210619034043.199220-7-tientzu@chromium.org> <76c3343d-72e5-9df3-8924-5474ee698ef4@quicinc.com> <20210623183736.GA472@willie-the-truck> <19d4c7a2-744d-21e0-289c-a576e1f0e6f3@quicinc.com>
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On Wed, Jun 23, 2021 at 02:44:34PM -0400, Qian Cai wrote:
> is_swiotlb_force_bounce at /usr/src/linux-next/./include/linux/swiotlb.h:119
> 
> is_swiotlb_force_bounce() was the new function introduced in this patch here.
> 
> +static inline bool is_swiotlb_force_bounce(struct device *dev)
> +{
> +	return dev->dma_io_tlb_mem->force_bounce;
> +}

To me the crash looks like dev->dma_io_tlb_mem is NULL.  Can you
turn this into :

	return dev->dma_io_tlb_mem && dev->dma_io_tlb_mem->force_bounce;

for a quick debug check?