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

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Message-ID: <9412dba0-8e52-3361-f51d-0a8c70364d7f@chelsio.com>
Date:   Tue, 26 Sep 2017 18:34:54 +0530
From:   Harsh Jain <Harsh@...lsio.com>
To:     Dan Williams <dan.j.williams@...el.com>,
        Casey Leedom <leedom@...lsio.com>
Cc:     Robin Murphy <robin.murphy@....com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "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>,
        "dwmw2@...radead.org" <dwmw2@...radead.org>,
        David Woodhouse <David.Woodhouse@...el.com>
Subject: Re: DMA error when sg->offset value is greater than PAGE_SIZE in
 Intel IOMMU



On 26-09-2017 01:41, Dan Williams wrote:
> On Mon, Sep 25, 2017 at 1:05 PM, Casey Leedom <leedom@...lsio.com> wrote:
>> | From: Dan Williams <dan.j.williams@...el.com>
>> | Sent: Monday, September 25, 2017 12:31 PM
>> | ...
>> | IIUC it looks like this has been broken ever since commit e1605495c716
>> | "intel-iommu: Introduce domain_sg_mapping() to speed up
>> | intel_map_sg()". I.e. it looks like the calculation for pte_val should
>> | be:
>> |
>> |     pteval = (page_to_phys(sg_page(sg)) + sg->offset) | prot;
>>
>> Hhmmm, shouldn't that be:
>>
>>     pteval = (page_to_phys(sg_page(sg)) + (sg->offset>>PAGE_SHIFT)) | prot;
> Yes, I think you're right. We do want to mask off the page-unaligned
> portion of sg->offset.
Tried changing above line in "__domain_mapping" but didn't help.