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vfio: remove useless judgement

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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 8f0d5bb95f ("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>
Reviewed-by: Jason Gunthorpe <jgg@ziepe.ca>
Link: https://lore.kernel.org/r/20220627035109.73745-1-lizhe.67@bytedance.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
This commit is contained in:
Li Zhe 2022-06-27 11:51:09 +08:00 committed by Alex Williamson
parent d1877e639b
commit ffed0518d8
1 changed files with 0 additions and 6 deletions
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6
drivers/vfio/vfio_iommu_type1.c
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@ -1377,12 +1377,6 @@ again:
if (!iommu->v2 && iova > dma->iova)
break;
/*
* Task with same address space who mapped this iova range is
* allowed to unmap the iova range.
*/
if (dma->task->mm != current->mm)
break;
if (invalidate_vaddr) {
if (dma->vaddr_invalid) {