Re: [Qemu-devel] [Qemu-arm] [PATCH v4 0/5] virtio-iommu: VFIO integration

[Linu Cherian <linuc.decode@gmail.com>]

Hi Eric,


On Wed Sep 27, 2017 at 11:24:01AM +0200, Auger Eric wrote:
> Hi Linu,
> 
> On 27/09/2017 11:21, Linu Cherian wrote:
> > On Wed Sep 27, 2017 at 10:55:07AM +0200, Auger Eric wrote:
> >> Hi Linu,
> >>
> >> On 27/09/2017 10:30, Bharat Bhushan wrote:
> >>> Hi,
> >>>
> >>>> -----Original Message-----
> >>>> From: Linu Cherian [mailto:linuc.decode@gmail.com]
> >>>> Sent: Wednesday, September 27, 2017 1:11 PM
> >>>> To: Bharat Bhushan <bharat.bhushan@nxp.com>
> >>>> Cc: eric.auger@redhat.com; eric.auger.pro@gmail.com;
> >>>> peter.maydell@linaro.org; alex.williamson@redhat.com; mst@redhat.com;
> >>>> qemu-arm@nongnu.org; qemu-devel@nongnu.org; kevin.tian@intel.com;
> >>>> marc.zyngier@arm.com; tn@semihalf.com; will.deacon@arm.com;
> >>>> drjones@redhat.com; robin.murphy@arm.com; christoffer.dall@linaro.org;
> >>>> bharatb.yadav@gmail.com
> >>>> Subject: Re: [Qemu-arm] [PATCH v4 0/5] virtio-iommu: VFIO integration
> >>>>
> >>>> Hi,
> >>>>
> >>>> On Wed Sep 27, 2017 at 12:03:15PM +0530, Bharat Bhushan wrote:
> >>>>> This patch series integrates VFIO/VHOST with virtio-iommu.
> >>>>>
> >>>>> This version is mainly about rebasing on v4 version on virtio-iommu
> >>>>> device framework from Eric Augur and addresing review comments.
> >>>>>
> >>>>> This patch series allows PCI pass-through using virtio-iommu.
> >>>>>
> >>>>> This series is based on:
> >>>>>  - virtio-iommu kernel driver by Jean-Philippe Brucker
> >>>>>     [1] [RFC] virtio-iommu version 0.4
> >>>>>     git://linux-arm.org/virtio-iommu.git branch viommu/v0.4
> >>
> >> Just to make sure, do you use the v0.4 virtio-iommu driver from above
> >> branch?
> >>
> >> Thanks
> > 
> > I am using git://linux-arm.org/linux-jpb.git branch virtio-iommu/v0.4.
> > Hope you are referring to the same.
> 
> Yes that's the right one. I will also investigate on my side this afternoon.
> 
> Thanks
> 
> Eric

With the below workaround, atleast ping works for me.

diff --git a/drivers/iommu/virtio-iommu.c b/drivers/iommu/virtio-iommu.c
index 249964a..2904617 100644
--- a/drivers/iommu/virtio-iommu.c
+++ b/drivers/iommu/virtio-iommu.c
        .attach_dev             = viommu_attach_dev,
        .map                    = viommu_map,
        .unmap                  = viommu_unmap,
-       .map_sg                 = viommu_map_sg,
+       .map_sg                 = default_iommu_map_sg,
        .iova_to_phys           = viommu_iova_to_phys,
        .add_device             = viommu_add_device,
        .remove_device          = viommu_remove_device,


Looks like the qemu backend doesnt have support to handle the map requests from 
virtio_iommu_map_sg, since it  merges multiple map requests into one with 
mapsize larger than page size(for eg. 0x5000). 

Atleast vfio_get_vaddr called from vfio_iommu_map_notify in Qemu expects 
the map size to be a power of 2.

 if (len & iotlb->addr_mask) {
        error_report("iommu has granularity incompatible with target AS");
        return false;
    }

Just trying to understand how this is not hitting in your case. 
 
-- 
Linu cherian