linux-kernel - Re: DMA error when sg->offset value is greater than PAGE

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Message-ID: <6d2af675-7b97-6eaf-4daa-d7bf80a05923@chelsio.com>
Date:   Tue, 26 Sep 2017 17:51:06 +0530
From:   Harsh Jain <Harsh@...lsio.com>
To:     Casey Leedom <leedom@...lsio.com>,
        "Raj, Ashok" <ashok.raj@...el.com>
Cc:     Robin Murphy <robin.murphy@....com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        David Woodhouse <David.Woodhouse@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        "dwmw2@...radead.org" <dwmw2@...radead.org>
Subject: Re: DMA error when sg->offset value is greater than PAGE_SIZE in
 Intel IOMMU

Find attached new set of log. After repeated tries it panics.


On 26-09-2017 09:16, Harsh Jain wrote:
> On 26-09-2017 00:16, Casey Leedom wrote:
>> | From: Raj, Ashok <ashok.raj@...el.com>
>> | Sent: Monday, September 25, 2017 8:54 AM
>> |
>> | Not sure how the page->offset would end up being greater than page-size?
> Refer below
>> |
>> | If you have additional traces, please send them by.
>> |
>> | Is this a new driver? wondering how we didn't run into this?
>>
>>   According to Herbert Xu and one of our own engineers, it's actually legal
>> for Scatter/Gather Lists to have this.  This isn't my area of expertise
>> though so I'm just passing that on.
>>
>>   I've asked our team to produce a detailed trace of the exact
>> Scatter/Gather Lists they're seeing and what ends up coming out of the DMA
>> Mappings, etc.  They're in India, so I expect that they'll have this for you
>> by tomorrow morning.
> Below mentioned log was already there in 1st mail. Copied here for easy reference. Let me know if you need
> additional traces.
>
> 1) IN esp_output() "__skb_to_sgvec()" convert skb frags to scatter gather list. 
> At that moment sg->offset was 4094.
> 2) From esp_output control reaches to "crypto_authenc_encrypt()". Here in 
> "scatterwalk_ffwd()" sg->offset become 4110.
> 3) Same sg list received by chelsio crypto driver(chcr). When chcr try to do 
> DMA mapping it starts giving DMA errors.
>
> Following error observed. first two prints are added for debugging in chcr. 
> Kernel version used to reproduce is 4.9.28 on x86_64 with Page size 4K.
>
> Sep 15 12:40:52 heptagon kernel: process_cipher req src ffff8803cb41f0a8
> Sep 15 12:40:52 heptagon kernel: ========= issue    hit offset:4110 ======= 
> dma_addr f24b000e ==> DMA mapped address returned by dma_map_sg()
>
> Sep 15 12:40:52 heptagon kernel: DMAR: DRHD: handling fault status reg 2
> Sep 15 12:40:52 heptagon kernel: DMAR: [DMA Write] Request device [02:00.4] 
> fault addr f24b0000 [fault reason 05] PTE Write access is not set
>
>> Casey


View attachment "dma_err_ssh_from_a_to_c.log" of type "text/plain" (17301 bytes)