RE: [PATCH] iommu/dma: Setup iova_domain granule for IOMMU_DMA_MSI cookies

[Bharat Bhushan]

Hi Robin,

I faced same issue on our platform and debugged to get the root cause of the issue. Also fixed in somewhat similar way, cleared iova_off and not change size for if cookie->type is  IOMMU_DMA_MSI_COOKIE. Anyways that was not as good as below changes.

While just now I saw this was already discussed and solved. Should have looked earlier to save time, but the debugging was some learning experience ð 

I have tested your below change and it works fine on NXP platform.

Thanks
-Bharat

> -----Original Message-----
> From: iommu-bounces@xxxxxxxxxxxxxxxxxxxxxxxxxx [mailto:iommu-
> bounces@xxxxxxxxxxxxxxxxxxxxxxxxxx] On Behalf Of Shanker Donthineni
> Sent: Thursday, April 13, 2017 8:00 PM
> To: Robin Murphy <robin.murphy@xxxxxxx>; Nate Watterson
> <nwatters@xxxxxxxxxxxxxx>; Joerg Roedel <joro@xxxxxxxxxx>;
> iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH] iommu/dma: Setup iova_domain granule for
> IOMMU_DMA_MSI cookies
> 
> Hi Robin,
> 
> I tested your changes and the device pass-through feature works fine on
> QDF2400 server platform. Maybe Nate comments on the patch contents but
> it fixes the problem.
> 
> 
> @@ -317,13 +317,13 @@ static void iommu_dma_free_iova(struct
> iommu_dma_cookie *cookie,
>                 dma_addr_t iova, size_t size)  {
>         struct iova_domain *iovad = &cookie->iovad;
> -       unsigned long shift = iova_shift(iovad);
> 
>         /* The MSI case is only ever cleaning up its most recent allocation */
>         if (cookie->type == IOMMU_DMA_MSI_COOKIE)
>                 cookie->msi_iova -= size;
>         else
> -               free_iova_fast(iovad, iova >> shift, size >> shift);
> +               free_iova_fast(iovad, iova_pfn(iovad, iova),
> +                              size >> iova_shift(iovad));
>  }
> 
>  static void __iommu_dma_unmap(struct iommu_domain *domain,
> dma_addr_t dma_addr, @@ -538,11 +538,14 @@ static dma_addr_t
> __iommu_dma_map(struct device *dev, phys_addr_t phys,  {
>         struct iommu_domain *domain = iommu_get_domain_for_dev(dev);
>         struct iommu_dma_cookie *cookie = domain->iova_cookie;
> -       struct iova_domain *iovad = &cookie->iovad;
> -       size_t iova_off = iova_offset(iovad, phys);
> +       size_t iova_off = 0;
>         dma_addr_t iova;
> 
> -       size = iova_align(iovad, size + iova_off);
> +       if (cookie->type == IOMMU_DMA_IOVA_COOKIE) {
> +               iova_off = iova_offset(&cookie->iovad, phys);
> +               size = iova_align(&cookie->iovad, size + iova_off);
> +       }
> 
> 
> On 04/13/2017 06:21 AM, Robin Murphy wrote:
> > Hi Nate,
> >
> > On 13/04/17 09:55, Nate Watterson wrote:
> >> Currently, the __iommu_dma_{map/free} functions call
> >> iova_{offset/align} making them unsuitable for use with iommu_domains
> >> having an IOMMU_DMA_MSI cookie since the cookie's iova_domain
> member, iovad, is uninitialized.
> >>
> >> Now that iommu_dma_get_msi_page() calls __iommu_dma_map()
> regardless
> >> of cookie type, failures are being seen when mapping MSI target
> >> addresses for devices attached to UNMANAGED domains. To work
> around
> >> this issue, the iova_domain granule for IOMMU_DMA_MSI cookies is
> >> initialized to the value returned by cookie_msi_granule().
> > Oh bum. Thanks for the report.
> >
> > However, I really don't like bodging around it with deliberate
> > undefined behaviour. Fixing things properly doesn't seem too hard:
> >
> > ----->8-----
> > diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> > index 8348f366ddd1..62618e77bedc 100644
> > --- a/drivers/iommu/dma-iommu.c
> > +++ b/drivers/iommu/dma-iommu.c
> > @@ -396,13 +396,13 @@ static void iommu_dma_free_iova(struct
> > iommu_dma_cookie *cookie,
> >                 dma_addr_t iova, size_t size)  {
> >         struct iova_domain *iovad = &cookie->iovad;
> > -       unsigned long shift = iova_shift(iovad);
> >
> >         /* The MSI case is only ever cleaning up its most recent
> > allocation */
> >         if (cookie->type == IOMMU_DMA_MSI_COOKIE)
> >                 cookie->msi_iova -= size;
> >         else
> > -               free_iova_fast(iovad, iova >> shift, size >> shift);
> > +               free_iova_fast(iovad, iova_pfn(iovad, iova),
> > +                               size >> iova_shift(iovad));
> >  }
> >
> >  static void __iommu_dma_unmap(struct iommu_domain *domain,
> dma_addr_t
> > dma_addr, @@ -617,11 +617,14 @@ static dma_addr_t
> > __iommu_dma_map(struct device *dev, phys_addr_t phys,  {
> >         struct iommu_domain *domain = iommu_get_domain_for_dev(dev);
> >         struct iommu_dma_cookie *cookie = domain->iova_cookie;
> > -       struct iova_domain *iovad = &cookie->iovad;
> > -       size_t iova_off = iova_offset(iovad, phys);
> > +       size_t iova_off = 0;
> >         dma_addr_t iova;
> >
> > -       size = iova_align(iovad, size + iova_off);
> > +       if (cookie->type == IOMMU_DMA_IOVA_COOKIE) {
> > +               iova_off = iova_offset(&cookie->iovad, phys);
> > +               size = iova_align(&cookie->iovad, size + iova_off);
> > +       }
> > +
> >         iova = iommu_dma_alloc_iova(domain, size, dma_get_mask(dev),
> dev);
> >         if (!iova)
> >                 return DMA_ERROR_CODE;
> > -----8<-----
> >
> > Untested, and you'll probably want to double-check it anyway given
> > that the original oversight was mine in the first place ;)
> >
> > Robin.
> >
> >> Fixes: a44e6657585b ("iommu/dma: Clean up MSI IOVA allocation")
> >> Signed-off-by: Nate Watterson <nwatters@xxxxxxxxxxxxxx>
> >> ---
> >>  drivers/iommu/dma-iommu.c | 10 ++++++++++
> >>  1 file changed, 10 insertions(+)
> >>
> >> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> >> index 8348f366..d7b0816 100644
> >> --- a/drivers/iommu/dma-iommu.c
> >> +++ b/drivers/iommu/dma-iommu.c
> >> @@ -127,6 +127,16 @@ int iommu_get_msi_cookie(struct
> iommu_domain
> >> *domain, dma_addr_t base)
> >>
> >>  	cookie->msi_iova = base;
> >>  	domain->iova_cookie = cookie;
> >> +
> >> +	/*
> >> +	 * Setup granule for compatibility with __iommu_dma_{alloc/free}
> and
> >> +	 * add a compile time check to ensure that writing granule won't
> >> +	 * clobber msi_iova.
> >> +	 */
> >> +	cookie->iovad.granule = cookie_msi_granule(cookie);
> >> +	BUILD_BUG_ON(offsetof(struct iova_domain, granule) <
> >> +			sizeof(cookie->msi_iova));
> >> +
> >>  	return 0;
> >>  }
> >>  EXPORT_SYMBOL(iommu_get_msi_cookie);
> >>
> 
> --
> Shanker Donthineni
> Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm
> Technologies, Inc.
> Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux
> Foundation Collaborative Project.
> 
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