Messages in this thread | | | Date | Fri, 24 Jun 2022 21:13:04 -0300 | From | Jason Gunthorpe <> | Subject | Re: [RFC] vfio: remove useless judgement |
| |
On Thu, Jun 23, 2022 at 07:56:03PM +0800, lizhe.67@bytedance.com wrote: > From: Li Zhe <lizhe.67@bytedance.com> > > In function vfio_dma_do_unmap(), we currently prevent process to unmap > vfio dma region whose mm_struct is different from the vfio_dma->task. > In our virtual machine scenario which is using kvm and qemu, this > judgement stops us from liveupgrading our qemu, which uses fork() && > exec() to load the new binary but the new process cannot do the > VFIO_IOMMU_UNMAP_DMA action during vm exit because of this judgement. > > This judgement is added in commit 8f0d5bb95f76 ("vfio iommu type1: Add > task structure to vfio_dma") for the security reason. But it seems that > no other task who has no family relationship with old and new process > can get the same vfio_dma struct here for the reason of resource > isolation. So this patch delete it. > > Signed-off-by: Li Zhe <lizhe.67@bytedance.com> > --- > drivers/vfio/vfio_iommu_type1.c | 6 ------ > 1 file changed, 6 deletions(-)
I'm inclined to agree with this reasoning and deliberately did not include a similar check in iommufd. Any process with access to the container FD should be able to manipulate the IOVA space.
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Jason
| |