Re: DMA error when sg->offset value is greater than PAGE_SIZE in Intel IOMMU

From	"Raj, Ashok" <ashok.raj@intel.com>
Newsgroups	linux.kernel
Subject	Re: DMA error when sg->offset value is greater than PAGE_SIZE in Intel IOMMU
Date	2017-09-25 23:50 +0200
Message-ID	<utJqi-3Hi-21@gated-at.bofh.it> (permalink)
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Hi

On Mon, Sep 25, 2017 at 01:11:04PM -0700, Dan Williams wrote:
> On Mon, Sep 25, 2017 at 1:05 PM, Casey Leedom <leedom@chelsio.com> wrote:
> > | From: Dan Williams <dan.j.williams@intel.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.

Shoulnd't we normalize the entire sg_page(sg) + sg_offset.

if when you only mask the page-unaligned portion i suspect you might be
pointing to a different region?

something like (sg_page(sg) + (sg->offset << VTD_PAGE_SHIFT)) 

then add the unaligned part.. sg->offset>>VTD_PAGE_SHIFT

Is this happening because you are using a 2M page? not sure what triggers
this or causes the driver to get passed in larger than 4K offset, or 
running 32bit kernel?

if its legal to get passed in such odd values, we should fix IOMMU driver to 
handle it properly, otherwise we should atleast fail those requests.

Cheers,
Ashok

Thread

DMA error when sg->offset value is greater than PAGE_SIZE in Intel  IOMMU Harsh Jain <Harsh@chelsio.com> - 2017-09-16 08:20 +0200
  Re: DMA error when sg->offset value is greater than PAGE_SIZE in  Intel IOMMU Herbert Xu <herbert@gondor.apana.org.au> - 2017-09-20 10:10 +0200
    Re: DMA error when sg->offset value is greater than PAGE_SIZE in  Intel IOMMU Robin Murphy <robin.murphy@arm.com> - 2017-09-20 12:20 +0200
      Re: DMA error when sg->offset value is greater than PAGE_SIZE in  Intel IOMMU Harsh Jain <Harsh@chelsio.com> - 2017-09-20 13:30 +0200
      Re: DMA error when sg->offset value is greater than PAGE_SIZE in  Intel IOMMU Casey Leedom <leedom@chelsio.com> - 2017-09-25 19:50 +0200
        Re: DMA error when sg->offset value is greater than PAGE_SIZE in  Intel IOMMU "Raj, Ashok" <ashok.raj@intel.com> - 2017-09-25 20:50 +0200
          Re: DMA error when sg->offset value is greater than PAGE_SIZE in  Intel IOMMU Casey Leedom <leedom@chelsio.com> - 2017-09-25 20:50 +0200
            Re: DMA error when sg->offset value is greater than PAGE_SIZE in  Intel IOMMU Harsh Jain <Harsh@chelsio.com> - 2017-09-26 05:50 +0200
              Re: DMA error when sg->offset value is greater than PAGE_SIZE in  Intel IOMMU Harsh Jain <Harsh@chelsio.com> - 2017-09-26 14:30 +0200
                Re: DMA error when sg->offset value is greater than PAGE_SIZE in  Intel IOMMU Robin Murphy <robin.murphy@arm.com> - 2017-09-26 16:30 +0200
        Re: DMA error when sg->offset value is greater than PAGE_SIZE in  Intel IOMMU Dan Williams <dan.j.williams@intel.com> - 2017-09-25 21:40 +0200
          Re: DMA error when sg->offset value is greater than PAGE_SIZE in  Intel IOMMU Casey Leedom <leedom@chelsio.com> - 2017-09-25 22:10 +0200
            Re: DMA error when sg->offset value is greater than PAGE_SIZE in  Intel IOMMU Dan Williams <dan.j.williams@intel.com> - 2017-09-25 22:20 +0200
              Re: DMA error when sg->offset value is greater than PAGE_SIZE in  Intel IOMMU "Raj, Ashok" <ashok.raj@intel.com> - 2017-09-25 23:50 +0200
                Re: DMA error when sg->offset value is greater than PAGE_SIZE in  Intel IOMMU Casey Leedom <leedom@chelsio.com> - 2017-09-26 01:50 +0200
              Re: DMA error when sg->offset value is greater than PAGE_SIZE in  Intel IOMMU Harsh Jain <Harsh@chelsio.com> - 2017-09-26 15:10 +0200
    Re: DMA error when sg->offset value is greater than PAGE_SIZE in  Intel IOMMU Harsh Jain <Harsh@chelsio.com> - 2017-09-20 13:40 +0200
    Re: DMA error when sg->offset value is greater than PAGE_SIZE in  Intel IOMMU David Woodhouse <dwmw2@infradead.org> - 2017-09-25 20:50 +0200
      Re: DMA error when sg->offset value is greater than PAGE_SIZE in  Intel IOMMU Casey Leedom <leedom@chelsio.com> - 2017-09-25 22:20 +0200
      Re: DMA error when sg->offset value is greater than PAGE_SIZE in  Intel IOMMU Harsh Jain <Harsh@chelsio.com> - 2017-09-26 13:20 +0200

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