Re: [PATCH v4 0/5] vfio: type1: support for ARM SMMUS with VFIO_IOMMU_TYPE1

[Alex Williamson <alex.williamson@redhat.com>]

On Tue, 2015-03-03 at 18:46 +0100, Eric Auger wrote:
> Hi Baptiste,
> 
> In "vfio: type1: implement the VFIO_DMA_MAP_FLAG_NOEXEC flag" you still
> kept domain->caps |= IOMMU_CAP_NOEXEC so potentially overwriting 1<<
> IOMMU_CAP_CACHE_COHERENCY I guess.
> 
> Sorry I do not have this 4th patch file in my mailbox.
> 
> Best Regards
> 
> Eric
> 
> 	if (iommu_capable(bus, IOMMU_CAP_CACHE_COHERENCY))
> 		domain->caps |= (1 << IOMMU_CAP_CACHE_COHERENCY);
> 
> 	if (iommu_capable(bus, IOMMU_CAP_NOEXEC))
> 		domain->caps |= IOMMU_CAP_NOEXEC;


Patch 4/5 has problems too, vfio_domains_have_iommu_cap() is called with
IOMMU_CAP_CACHE_COHERENCY, but nobody is shifting that into a bitmap
before doing the comparison.

TBH, I don't see the point of creating this artificial bitmap out of the
capabilities.  Why can't we keep everything in the domain of actual
flags passed to iommu_ops functions?  It's just silly to test for cached
capability and re-invent the mapping flags on every mapping call and
it's just as easy to generalize a test using the actual flags as to use
the capabilities, perhaps easier.  Thanks,

Alex



> On 03/02/2015 05:58 PM, Baptiste Reynal wrote:
> > This patch series makes the VFIO_IOMMU_TYPE1 driver buildable on ARM, so it
> > may be used with ARM SMMUs. It also adds support for the IOMMU_NOEXEC flag
> > supported by SMMUs adhering to the ARM SMMU specification so the VFIO user can
> > specify whether the target memory can be executed by the device behind the
> > SMMU.
> > 
> > Changes from v3:
> >  - Rebased on linux v4.0-rc1
> >  - Use bit shifting for domain->caps
> >  - Baptiste Reynal is the new maintainer of this serie
> > Changes from v2:
> >  - Rebased on latest iommu/next branch by Joerg Roedel
> > Changes from v1:
> >  - Bugfixes and corrected some typos
> >  - Use enum for VFIO IOMMU driver capabilities
> > 
> > Antonios Motakis (5):
> >   vfio: implement iommu driver capabilities with an enum
> >   vfio: introduce the VFIO_DMA_MAP_FLAG_NOEXEC flag
> >   vfio: type1: replace domain wide protection flags with supported
> >     capabilities
> >   vfio: type1: replace vfio_domains_have_iommu_cache with generic
> >     function
> >   vfio: type1: implement the VFIO_DMA_MAP_FLAG_NOEXEC flag
> > 
> >  drivers/vfio/vfio_iommu_type1.c | 91 +++++++++++++++++++++++++++++------------
> >  include/uapi/linux/vfio.h       | 30 ++++++++------
> >  2 files changed, 81 insertions(+), 40 deletions(-)
> > 
> 
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