linux-kernel - Re: [PATCH V2 5/5] DO NOT MERGE: iommu: disable list appending in dma-iommu

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Date:   Sat, 12 Sep 2020 11:13:44 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     baolu.lu@...ux.intel.com, Tom Murphy <murphyt7@....ie>,
        intel-gfx@...ts.freedesktop.org,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        iommu@...ts.linux-foundation.org,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        David Woodhouse <dwmw2@...radead.org>
Subject: Re: [PATCH V2 5/5] DO NOT MERGE: iommu: disable list appending in
 dma-iommu

On 2020/9/9 15:06, Christoph Hellwig wrote:
> On Wed, Sep 09, 2020 at 09:43:09AM +0800, Lu Baolu wrote:
>> +       /*
>> +        * The Intel graphic device driver is used to assume that the
>> returned
>> +        * sg list is not combound. This blocks the efforts of converting
>> the
> 
> This adds pointless overly long lines.
> 
>> +        * Intel IOMMU driver to dma-iommu api's. Add this quirk to make the
>> +        * device driver work and should be removed once it's fixed in i915
>> +        * driver.
>> +        */
>> +       if (dev_is_pci(dev) &&
>> +           to_pci_dev(dev)->vendor == PCI_VENDOR_ID_INTEL &&
>> +           (to_pci_dev(dev)->class >> 16) == PCI_BASE_CLASS_DISPLAY) {
>> +               for_each_sg(sg, s, nents, i) {
>> +                       unsigned int s_iova_off = sg_dma_address(s);
>> +                       unsigned int s_length = sg_dma_len(s);
>> +                       unsigned int s_iova_len = s->length;
>> +
>> +                       s->offset += s_iova_off;
>> +                       s->length = s_length;
>> +                       sg_dma_address(s) = dma_addr + s_iova_off;
>> +                       sg_dma_len(s) = s_length;
>> +                       dma_addr += s_iova_len;
>> +               }
>> +
>> +               return nents;
>> +       }
> 
> This wants an IS_ENABLED() check.  And probably a pr_once reminding
> of the workaround.
> 

Will fix in the next version.

Best regards,
baolu