[dpdk-dev] [PATCH] doc/guides/rel_notes: Add known issue for IOMMU attributes read

[Xu, Rosen]

Hi Anatoly,

> -----Original Message-----
> From: Burakov, Anatoly
> Sent: Tuesday, May 15, 2018 1:10
> To: Xu, Rosen <rosen.xu at intel.com>; dev at dpdk.org
> Cc: gaetan.rivet at 6wind.com; Mcnamara, John <john.mcnamara at intel.com>;
> Pei, Yulong <yulong.pei at intel.com>; stable at dpdk.org
> Subject: Re: [PATCH] doc/guides/rel_notes: Add known issue for IOMMU
> attributes read
> 
> On 14-May-18 11:44 AM, Rosen Xu wrote:
> > Read IOMMU attributes from linux kernle 4.10.0 error.
> 
> s/kernle/kernel :)

Fixed
 
> >
> > Cc: stable at dpdk.org
> >
> > Signed-off-by: Rosen Xu <rosen.xu at intel.com>
> > ---
> >   doc/guides/rel_notes/known_issues.rst | 21 +++++++++++++++++++++
> >   1 file changed, 21 insertions(+)
> >
> > diff --git a/doc/guides/rel_notes/known_issues.rst
> > b/doc/guides/rel_notes/known_issues.rst
> > index afcc2c4..74876ff 100644
> > --- a/doc/guides/rel_notes/known_issues.rst
> > +++ b/doc/guides/rel_notes/known_issues.rst
> > @@ -714,3 +714,24 @@ igb_uio can not be used when running l3fwd-
> power
> >
> >   **Driver/Module**:
> >      ``igb_uio`` module.
> > +
> > +
> > +linux kernel iommu attribute read error
> 
> Should this be capitalized?

Fixed
 
> > +---------------------------------------
> > +
> > +**Description**:
> > +   Read immu attributes from /sys/devices/virtual/iommu/dmarXXX/intel-
> iommu/cap in linux kernel
> > +   4.10.0 error. That because the link between the iommu sysfs-device and
> the struct intel_iommu
> > +   is no longer stored as driver-data.
> 
> s/immu/IOMMU/, and i think this needs to be rewritten to something like as
> follows:
> 
> Reading IOMMU attributes from

Fixed

> /sys/devices/virtual/iommu/dmarXXX/intel-iommu/cap in Linux kernel
> 4.10.0 results in an error. This is because the link between the IOMMU sysfs-
> device and struct intel_iommu is no longer stored as driver-data.
> 
> (i have no idea what that last sentence means, maybe someone could help
> provide a better explanation?)

This linux kernel issue is fixed, around the 4.10/4.11 timeframe.
commit a7fdb6e648fb10a4174483b5fc4dac9c25bd2093
Author: Joerg Roedel <jroedel at suse.de>
Date:   Tue Feb 28 13:57:18 2017 +0100

    iommu/vt-d: Fix crash when accessing VT-d sysfs entries
    
    The link between the iommu sysfs-device and the struct
    intel_iommu is no longer stored as driver-data. Update the
    code to use the new access method.
 
> > +
> > +**Implication**:
> > +   When insmod ``vfio-pci`` and running testpmd APP, it doesn't initiate
> properly.
> 
> Should probably be reworded as follows:
> 
> When binding devices to VFIO and attempting to run testpmd application,
> testpmd (and other DPDK applications) will not initialize.

Fixed.
 
> > +
> > +**Resolution/Workaround**:
> > +   Use other linux kernel version. It only happens in linux kernel 4.10.0.
> > +
> > +**Affected Environment/Platform**:
> > +   ALL OS of linux kernel 4.10.0.
> > +
> > +**Driver/Module**:
> > +   ``vfio-pci`` module.
> >
> 
> 
> --
> Thanks,
> Anatoly