Hi Peter, > -----Original Message----- > From: Peter Xu [mailto:pet...@redhat.com] > Sent: Wednesday, September 27, 2017 12:32 PM > To: Bharat Bhushan <bharat.bhus...@nxp.com> > Cc: eric.au...@redhat.com; eric.auger....@gmail.com; > peter.mayd...@linaro.org; alex.william...@redhat.com; m...@redhat.com; > qemu-...@nongnu.org; qemu-devel@nongnu.org; w...@redhat.com; > kevin.t...@intel.com; marc.zyng...@arm.com; t...@semihalf.com; > will.dea...@arm.com; drjo...@redhat.com; robin.mur...@arm.com; > christoffer.d...@linaro.org; bharatb.ya...@gmail.com > Subject: Re: [PATCH v4 0/5] virtio-iommu: VFIO integration > > On Wed, Sep 27, 2017 at 06:46:18AM +0000, Bharat Bhushan wrote: > > Hi Peter, > > Hi, Bharat! > > > > > While vfio with virtio-iommu I observed one issue, When virtio-iommu > device exists but guest kernel does not have virtio-iommu driver (not > enabled in Config) then IOMMU faults are reported on host. > > > > This is because no mapping is created in IOMMU, not even default > guest-physical to real-physical. While looking at vfio_listener_region_add(), > it > does not create initial mapping in IOMMU and relies on guest to create > mapping. Is this something known or I am missing something? > > For VT-d, the trick is played using dynamic IOMMU memory region. > Please refer to commit 558e0024a428 ("intel_iommu: allow dynamic switch of > IOMMU region") for more information. > > The whole idea is that, the IOMMU region will not be enabled only if the > guest enables that explicitly for the device. Otherwise (for your case, when > guest driver is not loaded at all), the IOMMU region is by default off, then > the default GPA region will be used to build up the mapping (just like when > we don't have vIOMMU at all). Thanks,
Thanks, I will analyze and see how we can use for virtio-iommu. Regards -Bharat > > -- > Peter Xu
